core, consensus: pluggable consensus engines (#3817)

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

61 files changed, 1682 insertions, 1427 deletions

diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index 3d7e96bf6..43f563159 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -27,6 +27,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -34,7 +35,6 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
@@ -61,7 +61,7 @@ func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
 	database, _ := ethdb.NewMemDatabase()
 	genesis := core.Genesis{Config: params.AllProtocolChanges, Alloc: alloc}
 	genesis.MustCommit(database)
-	blockchain, _ := core.NewBlockChain(database, genesis.Config, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	blockchain, _ := core.NewBlockChain(database, genesis.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	backend := &SimulatedBackend{database: database, blockchain: blockchain, config: genesis.Config}
 	backend.rollback()
 	return backend
diff --git a/cmd/evm/disasm.go b/cmd/evm/disasm.go
index 01a8c60ba..a78b2a8e1 100644
--- a/cmd/evm/disasm.go
+++ b/cmd/evm/disasm.go
@@ -20,10 +20,10 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"strings"
 
 	"github.com/ethereum/go-ethereum/core/asm"
 	cli "gopkg.in/urfave/cli.v1"
-	"strings"
 )
 
 var disasmCommand = cli.Command{
diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index cc6d3ac6a..e942d53c8 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -303,7 +303,15 @@ func startNode(ctx *cli.Context, stack *node.Node) {
 		if err := stack.Service(&ethereum); err != nil {
 			utils.Fatalf("ethereum service not running: %v", err)
 		}
-		if err := ethereum.StartMining(ctx.GlobalInt(utils.MinerThreadsFlag.Name)); err != nil {
+		if threads := ctx.GlobalInt(utils.MinerThreadsFlag.Name); threads > 0 {
+			type threaded interface {
+				SetThreads(threads int)
+			}
+			if th, ok := ethereum.Engine().(threaded); ok {
+				th.SetThreads(threads)
+			}
+		}
+		if err := ethereum.StartMining(); err != nil {
 			utils.Fatalf("Failed to start mining: %v", err)
 		}
 	}
diff --git a/cmd/geth/misccmd.go b/cmd/geth/misccmd.go
index 073c36beb..079f49310 100644
--- a/cmd/geth/misccmd.go
+++ b/cmd/geth/misccmd.go
@@ -26,9 +26,9 @@ import (
 	"strings"
 
 	"github.com/ethereum/go-ethereum/cmd/utils"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"gopkg.in/urfave/cli.v1"
 )
 
@@ -87,7 +87,7 @@ func makedag(ctx *cli.Context) error {
 				utils.Fatalf("Can't find dir")
 			}
 			fmt.Println("making DAG, this could take awhile...")
-			pow.MakeDataset(blockNum, dir)
+			ethash.MakeDataset(blockNum, dir)
 		}
 	default:
 		wrongArgs()
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 478e08834..acdf5d5dc 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -49,7 +50,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/nat"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rpc"
 	whisper "github.com/ethereum/go-ethereum/whisper/whisperv2"
 	"gopkg.in/urfave/cli.v1"
@@ -149,7 +149,7 @@ var (
 	}
 	TestNetFlag = cli.BoolFlag{
 		Name:  "testnet",
-		Usage: "Ropsten network: pre-configured test network",
+		Usage: "Ropsten network: pre-configured proof-of-work test network",
 	}
 	DevModeFlag = cli.BoolFlag{
 		Name:  "dev",
@@ -921,16 +921,16 @@ func MakeChain(ctx *cli.Context, stack *node.Node) (chain *core.BlockChain, chai
 	var err error
 	chainDb = MakeChainDatabase(ctx, stack)
 
-	seal := pow.PoW(pow.FakePow{})
+	engine := ethash.NewFaker()
 	if !ctx.GlobalBool(FakePoWFlag.Name) {
-		seal = pow.NewFullEthash("", 1, 0, "", 1, 0)
+		engine = ethash.New("", 1, 0, "", 1, 0)
 	}
 	config, _, err := core.SetupGenesisBlock(chainDb, MakeGenesis(ctx))
 	if err != nil {
 		Fatalf("%v", err)
 	}
 	vmcfg := vm.Config{EnablePreimageRecording: ctx.GlobalBool(VMEnableDebugFlag.Name)}
-	chain, err = core.NewBlockChain(chainDb, config, seal, new(event.TypeMux), vmcfg)
+	chain, err = core.NewBlockChain(chainDb, config, engine, new(event.TypeMux), vmcfg)
 	if err != nil {
 		Fatalf("Can't create BlockChain: %v", err)
 	}
diff --git a/consensus/consensus.go b/consensus/consensus.go
new file mode 100644
index 000000000..e318e57c0
--- /dev/null
+++ b/consensus/consensus.go
@@ -0,0 +1,94 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package consensus implements different Ethereum consensus engines.
+package consensus
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+// ChainReader defines a small collection of methods needed to access the local
+// blockchain during header and/or uncle verification.
+type ChainReader interface {
+	// Config retrieves the blockchain's chain configuration.
+	Config() *params.ChainConfig
+
+	// CurrentHeader retrieves the current header from the local chain.
+	CurrentHeader() *types.Header
+
+	// GetHeader retrieves a block header from the database by hash and number.
+	GetHeader(hash common.Hash, number uint64) *types.Header
+
+	// GetHeaderByNumber retrieves a block header from the database by number.
+	GetHeaderByNumber(number uint64) *types.Header
+
+	// GetBlock retrieves a block from the database by hash and number.
+	GetBlock(hash common.Hash, number uint64) *types.Block
+}
+
+// Engine is an algorithm agnostic consensus engine.
+type Engine interface {
+	// VerifyHeader checks whether a header conforms to the consensus rules of a
+	// given engine. Verifying the seal may be done optionally here, or explicitly
+	// via the VerifySeal method.
+	VerifyHeader(chain ChainReader, header *types.Header, seal bool) error
+
+	// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
+	// concurrently. The method returns a quit channel to abort the operations and
+	// a results channel to retrieve the async verifications (the order is that of
+	// the input slice).
+	VerifyHeaders(chain ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error)
+
+	// VerifyUncles verifies that the given block's uncles conform to the consensus
+	// rules of a given engine.
+	VerifyUncles(chain ChainReader, block *types.Block) error
+
+	// VerifySeal checks whether the crypto seal on a header is valid according to
+	// the consensus rules of the given engine.
+	VerifySeal(chain ChainReader, header *types.Header) error
+
+	// Prepare initializes the consensus fields of a block header according to the
+	// rules of a particular engine. The changes are executed inline.
+	Prepare(chain ChainReader, header *types.Header) error
+
+	// Finalize runs any post-transaction state modifications (e.g. block rewards)
+	// and assembles the final block.
+	//
+	// Note, the block header and state database might be updated to reflect any
+	// consensus rules that happen at finalization (e.g. block rewards).
+	Finalize(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,
+		uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error)
+
+	// Seal generates a new block for the given input block with the local miner's
+	// seal place on top.
+	Seal(chain ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error)
+
+	// APIs returns the RPC APIs this consensus engine provides.
+	APIs(chain ChainReader) []rpc.API
+}
+
+// PoW is a consensus engine based on proof-of-work.
+type PoW interface {
+	Engine
+
+	// Hashrate returns the current mining hashrate of a PoW consensus engine.
+	Hashrate() float64
+}
diff --git a/pow/ethash_algo.go b/consensus/ethash/algorithm.go
index 1e996785f..7e8fbfc37 100644
--- a/pow/ethash_algo.go
+++ b/consensus/ethash/algorithm.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package pow
+package ethash
 
 import (
 	"encoding/binary"
diff --git a/pow/ethash_algo_go1.7.go b/consensus/ethash/algorithm_go1.7.go
index ce05b3bb0..c34d041c3 100644
--- a/pow/ethash_algo_go1.7.go
+++ b/consensus/ethash/algorithm_go1.7.go
@@ -16,7 +16,7 @@
 
 // +build !go1.8
 
-package pow
+package ethash
 
 // cacheSize calculates and returns the size of the ethash verification cache that
 // belongs to a certain block number. The cache size grows linearly, however, we
diff --git a/pow/ethash_algo_go1.8.go b/consensus/ethash/algorithm_go1.8.go
index cac96cd5e..62bf4dec1 100644
--- a/pow/ethash_algo_go1.8.go
+++ b/consensus/ethash/algorithm_go1.8.go
@@ -16,7 +16,7 @@
 
 // +build go1.8
 
-package pow
+package ethash
 
 import "math/big"
 
diff --git a/pow/ethash_algo_go1.8_test.go b/consensus/ethash/algorithm_go1.8_test.go
index 57e0b0b7a..fdc302318 100644
--- a/pow/ethash_algo_go1.8_test.go
+++ b/consensus/ethash/algorithm_go1.8_test.go
@@ -16,7 +16,7 @@
 
 // +build go1.8
 
-package pow
+package ethash
 
 import "testing"
 
diff --git a/pow/ethash_algo_test.go b/consensus/ethash/algorithm_test.go
index 0605d70ad..7e4307a74 100644
--- a/pow/ethash_algo_test.go
+++ b/consensus/ethash/algorithm_test.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package pow
+package ethash
 
 import (
 	"bytes"
@@ -704,8 +704,8 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 		go func(idx int) {
 			defer pend.Done()
 
-			ethash := NewFullEthash(cachedir, 0, 1, "", 0, 0)
-			if err := ethash.Verify(block); err != nil {
+			ethash := New(cachedir, 0, 1, "", 0, 0)
+			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
 			}
 		}(i)
@@ -713,17 +713,6 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 	pend.Wait()
 }
 
-func TestTestMode(t *testing.T) {
-	head := &types.Header{Difficulty: big.NewInt(100)}
-	ethash := NewTestEthash()
-	nonce, mix := ethash.Search(types.NewBlockWithHeader(head), nil)
-	head.Nonce = types.EncodeNonce(nonce)
-	copy(head.MixDigest[:], mix)
-	if err := ethash.Verify(types.NewBlockWithHeader(head)); err != nil {
-		t.Error("unexpected Verify error:", err)
-	}
-}
-
 // Benchmarks the cache generation performance.
 func BenchmarkCacheGeneration(b *testing.B) {
 	for i := 0; i < b.N; i++ {
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
new file mode 100644
index 000000000..603be3e53
--- /dev/null
+++ b/consensus/ethash/consensus.go
@@ -0,0 +1,496 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethash
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"math/big"
+	"runtime"
+	"sync/atomic"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+	set "gopkg.in/fatih/set.v0"
+)
+
+// Ethash proof-of-work protocol constants.
+var (
+	blockReward *big.Int = big.NewInt(5e+18) // Block reward in wei for successfully mining a block
+	maxUncles            = 2                 // Maximum number of uncles allowed in a single block
+)
+
+var (
+	ErrInvalidChain        = errors.New("invalid header chain")
+	ErrParentUnknown       = errors.New("parent not known locally")
+	ErrFutureBlock         = errors.New("block in the future")
+	ErrLargeBlockTimestamp = errors.New("timestamp too big")
+	ErrZeroBlockTime       = errors.New("timestamp equals parent's")
+	ErrInvalidNumber       = errors.New("invalid block number")
+	ErrTooManyUncles       = errors.New("too many uncles")
+	ErrDuplicateUncle      = errors.New("duplicate uncle")
+	ErrUncleIsAncestor     = errors.New("uncle is ancestor")
+	ErrDanglingUncle       = errors.New("uncle's parent is not ancestor")
+	ErrNonceOutOfRange     = errors.New("nonce out of range")
+	ErrInvalidDifficulty   = errors.New("non-positive difficulty")
+	ErrInvalidMixDigest    = errors.New("invalid mix digest")
+	ErrInvalidPoW          = errors.New("invalid proof-of-work")
+)
+
+// VerifyHeader checks whether a header conforms to the consensus rules of the
+// stock Ethereum ethash engine.
+func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
+	// If we're running a full engine faking, accept any input as valid
+	if ethash.fakeFull {
+		return nil
+	}
+	// Short circuit if the header is known, or it's parent not
+	number := header.Number.Uint64()
+	if chain.GetHeader(header.Hash(), number) != nil {
+		return nil
+	}
+	parent := chain.GetHeader(header.ParentHash, number-1)
+	if parent == nil {
+		return ErrParentUnknown
+	}
+	// Sanity checks passed, do a proper verification
+	return ethash.verifyHeader(chain, header, parent, false, seal)
+}
+
+// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
+// concurrently. The method returns a quit channel to abort the operations and
+// a results channel to retrieve the async verifications.
+func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
+	// If we're running a full engine faking, accept any input as valid
+	if ethash.fakeFull {
+		abort, results := make(chan struct{}), make(chan error, len(headers))
+		for i := 0; i < len(headers); i++ {
+			results <- nil
+		}
+		return abort, results
+	}
+	// Spawn as many workers as allowed threads
+	workers := runtime.GOMAXPROCS(0)
+	if len(headers) < workers {
+		workers = len(headers)
+	}
+	// Create a task channel and spawn the verifiers
+	type result struct {
+		index int
+		err   error
+	}
+	inputs := make(chan int, workers)
+	outputs := make(chan result, len(headers))
+
+	var badblock uint64
+	for i := 0; i < workers; i++ {
+		go func() {
+			for index := range inputs {
+				// If we've found a bad block already before this, stop validating
+				if bad := atomic.LoadUint64(&badblock); bad != 0 && bad <= headers[index].Number.Uint64() {
+					outputs <- result{index: index, err: ErrInvalidChain}
+					continue
+				}
+				// We need to look up the first parent
+				var parent *types.Header
+				if index == 0 {
+					parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1)
+				} else if headers[index-1].Hash() == headers[index].ParentHash {
+					parent = headers[index-1]
+				}
+				// Ensure the validation is useful and execute it
+				var failure error
+				switch {
+				case chain.GetHeader(headers[index].Hash(), headers[index].Number.Uint64()-1) != nil:
+					outputs <- result{index: index, err: nil}
+				case parent == nil:
+					failure = ErrParentUnknown
+					outputs <- result{index: index, err: failure}
+				default:
+					failure = ethash.verifyHeader(chain, headers[index], parent, false, seals[index])
+					outputs <- result{index: index, err: failure}
+				}
+				// If a validation failure occurred, mark subsequent blocks invalid
+				if failure != nil {
+					number := headers[index].Number.Uint64()
+					if prev := atomic.LoadUint64(&badblock); prev == 0 || prev > number {
+						// This two step atomic op isn't thread-safe in that `badblock` might end
+						// up slightly higher than the block number of the first failure (if many
+						// workers try to write at the same time), but it's fine as we're mostly
+						// interested to avoid large useless work, we don't care about 1-2 extra
+						// runs. Doing "full thread safety" would involve mutexes, which would be
+						// a noticeable sync overhead on the fast spinning worker routines.
+						atomic.StoreUint64(&badblock, number)
+					}
+				}
+			}
+		}()
+	}
+	// Feed item indices to the workers until done, sorting and feeding the results to the caller
+	dones := make([]bool, len(headers))
+	errors := make([]error, len(headers))
+
+	abort := make(chan struct{})
+	returns := make(chan error, len(headers))
+
+	go func() {
+		defer close(inputs)
+
+		input, output := 0, 0
+		for i := 0; i < len(headers)*2; i++ {
+			var res result
+
+			// If there are tasks left, push to workers
+			if input < len(headers) {
+				select {
+				case inputs <- input:
+					input++
+					continue
+				case <-abort:
+					return
+				case res = <-outputs:
+				}
+			} else {
+				// Otherwise keep waiting for results
+				select {
+				case <-abort:
+					return
+				case res = <-outputs:
+				}
+			}
+			// A result arrived, save and propagate if next
+			dones[res.index], errors[res.index] = true, res.err
+			for output < len(headers) && dones[output] {
+				returns <- errors[output]
+				output++
+			}
+		}
+	}()
+	return abort, returns
+}
+
+// VerifyUncles verifies that the given block's uncles conform to the consensus
+// rules of the stock Ethereum ethash engine.
+func (ethash *Ethash) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
+	// If we're running a full engine faking, accept any input as valid
+	if ethash.fakeFull {
+		return nil
+	}
+	// Verify that there are at most 2 uncles included in this block
+	if len(block.Uncles()) > maxUncles {
+		return ErrTooManyUncles
+	}
+	// Gather the set of past uncles and ancestors
+	uncles, ancestors := set.New(), make(map[common.Hash]*types.Header)
+
+	number, parent := block.NumberU64()-1, block.ParentHash()
+	for i := 0; i < 7; i++ {
+		ancestor := chain.GetBlock(parent, number)
+		if ancestor == nil {
+			break
+		}
+		ancestors[ancestor.Hash()] = ancestor.Header()
+		for _, uncle := range ancestor.Uncles() {
+			uncles.Add(uncle.Hash())
+		}
+		parent, number = ancestor.ParentHash(), number-1
+	}
+	ancestors[block.Hash()] = block.Header()
+	uncles.Add(block.Hash())
+
+	// Verify each of the uncles that it's recent, but not an ancestor
+	for _, uncle := range block.Uncles() {
+		// Make sure every uncle is rewarded only once
+		hash := uncle.Hash()
+		if uncles.Has(hash) {
+			return ErrDuplicateUncle
+		}
+		uncles.Add(hash)
+
+		// Make sure the uncle has a valid ancestry
+		if ancestors[hash] != nil {
+			return ErrUncleIsAncestor
+		}
+		if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == block.ParentHash() {
+			return ErrDanglingUncle
+		}
+		if err := ethash.verifyHeader(chain, uncle, ancestors[uncle.ParentHash], true, true); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// verifyHeader checks whether a header conforms to the consensus rules of the
+// stock Ethereum ethash engine.
+//
+// See YP section 4.3.4. "Block Header Validity"
+func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *types.Header, uncle bool, seal bool) error {
+	// Ensure that the header's extra-data section is of a reasonable size
+	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
+		return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), params.MaximumExtraDataSize)
+	}
+	// Verify the header's timestamp
+	if uncle {
+		if header.Time.Cmp(math.MaxBig256) > 0 {
+			return ErrLargeBlockTimestamp
+		}
+	} else {
+		if header.Time.Cmp(big.NewInt(time.Now().Unix())) > 0 {
+			return ErrFutureBlock
+		}
+	}
+	if header.Time.Cmp(parent.Time) <= 0 {
+		return ErrZeroBlockTime
+	}
+	// Verify the block's difficulty based in it's timestamp and parent's difficulty
+	expected := CalcDifficulty(chain.Config(), header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
+	if expected.Cmp(header.Difficulty) != 0 {
+		return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected)
+	}
+	// Verify that the gas limit remains within allowed bounds
+	diff := new(big.Int).Set(parent.GasLimit)
+	diff = diff.Sub(diff, header.GasLimit)
+	diff.Abs(diff)
+
+	limit := new(big.Int).Set(parent.GasLimit)
+	limit = limit.Div(limit, params.GasLimitBoundDivisor)
+
+	if diff.Cmp(limit) >= 0 || header.GasLimit.Cmp(params.MinGasLimit) < 0 {
+		return fmt.Errorf("invalid gas limit: have %v, want %v += %v", header.GasLimit, parent.GasLimit, limit)
+	}
+	// Verify that the block number is parent's +1
+	if diff := new(big.Int).Sub(header.Number, parent.Number); diff.Cmp(big.NewInt(1)) != 0 {
+		return ErrInvalidNumber
+	}
+	// Verify the engine specific seal securing the block
+	if seal {
+		if err := ethash.VerifySeal(chain, header); err != nil {
+			return err
+		}
+	}
+	// If all checks passed, validate any special fields for hard forks
+	if err := misc.VerifyDAOHeaderExtraData(chain.Config(), header); err != nil {
+		return err
+	}
+	if err := misc.VerifyForkHashes(chain.Config(), header, uncle); err != nil {
+		return err
+	}
+	return nil
+}
+
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+// that a new block should have when created at time given the parent block's time
+// and difficulty.
+//
+// TODO (karalabe): Move the chain maker into this package and make this private!
+func CalcDifficulty(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
+		return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
+	}
+	return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
+}
+
+// Some weird constants to avoid constant memory allocs for them.
+var (
+	expDiffPeriod = big.NewInt(100000)
+	big10         = big.NewInt(10)
+	bigMinus99    = big.NewInt(-99)
+)
+
+// calcDifficultyHomestead is the difficulty adjustment algorithm. It returns
+// the difficulty that a new block should have when created at time given the
+// parent block's time and difficulty. The calculation uses the Homestead rules.
+func calcDifficultyHomestead(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
+	// algorithm:
+	// diff = (parent_diff +
+	//         (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
+	//        ) + 2^(periodCount - 2)
+
+	bigTime := new(big.Int).SetUint64(time)
+	bigParentTime := new(big.Int).SetUint64(parentTime)
+
+	// holds intermediate values to make the algo easier to read & audit
+	x := new(big.Int)
+	y := new(big.Int)
+
+	// 1 - (block_timestamp -parent_timestamp) // 10
+	x.Sub(bigTime, bigParentTime)
+	x.Div(x, big10)
+	x.Sub(common.Big1, x)
+
+	// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
+	if x.Cmp(bigMinus99) < 0 {
+		x.Set(bigMinus99)
+	}
+	// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
+	y.Div(parentDiff, params.DifficultyBoundDivisor)
+	x.Mul(y, x)
+	x.Add(parentDiff, x)
+
+	// minimum difficulty can ever be (before exponential factor)
+	if x.Cmp(params.MinimumDifficulty) < 0 {
+		x.Set(params.MinimumDifficulty)
+	}
+	// for the exponential factor
+	periodCount := new(big.Int).Add(parentNumber, common.Big1)
+	periodCount.Div(periodCount, expDiffPeriod)
+
+	// the exponential factor, commonly referred to as "the bomb"
+	// diff = diff + 2^(periodCount - 2)
+	if periodCount.Cmp(common.Big1) > 0 {
+		y.Sub(periodCount, common.Big2)
+		y.Exp(common.Big2, y, nil)
+		x.Add(x, y)
+	}
+	return x
+}
+
+// calcDifficultyFrontier is the difficulty adjustment algorithm. It returns the
+// difficulty that a new block should have when created at time given the parent
+// block's time and difficulty. The calculation uses the Frontier rules.
+func calcDifficultyFrontier(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	diff := new(big.Int)
+	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
+	bigTime := new(big.Int)
+	bigParentTime := new(big.Int)
+
+	bigTime.SetUint64(time)
+	bigParentTime.SetUint64(parentTime)
+
+	if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
+		diff.Add(parentDiff, adjust)
+	} else {
+		diff.Sub(parentDiff, adjust)
+	}
+	if diff.Cmp(params.MinimumDifficulty) < 0 {
+		diff.Set(params.MinimumDifficulty)
+	}
+
+	periodCount := new(big.Int).Add(parentNumber, common.Big1)
+	periodCount.Div(periodCount, expDiffPeriod)
+	if periodCount.Cmp(common.Big1) > 0 {
+		// diff = diff + 2^(periodCount - 2)
+		expDiff := periodCount.Sub(periodCount, common.Big2)
+		expDiff.Exp(common.Big2, expDiff, nil)
+		diff.Add(diff, expDiff)
+		diff = math.BigMax(diff, params.MinimumDifficulty)
+	}
+	return diff
+}
+
+// VerifySeal implements consensus.Engine, checking whether the given block satisfies
+// the PoW difficulty requirements.
+func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
+	// If we're running a fake PoW, accept any seal as valid
+	if ethash.fakeMode {
+		time.Sleep(ethash.fakeDelay)
+		if ethash.fakeFail == header.Number.Uint64() {
+			return ErrInvalidPoW
+		}
+		return nil
+	}
+	// If we're running a shared PoW, delegate verification to it
+	if ethash.shared != nil {
+		return ethash.shared.VerifySeal(chain, header)
+	}
+	// Sanity check that the block number is below the lookup table size (60M blocks)
+	number := header.Number.Uint64()
+	if number/epochLength >= uint64(len(cacheSizes)) {
+		// Go < 1.7 cannot calculate new cache/dataset sizes (no fast prime check)
+		return ErrNonceOutOfRange
+	}
+	// Ensure that we have a valid difficulty for the block
+	if header.Difficulty.Sign() <= 0 {
+		return ErrInvalidDifficulty
+	}
+	// Recompute the digest and PoW value and verify against the header
+	cache := ethash.cache(number)
+
+	size := datasetSize(number)
+	if ethash.tester {
+		size = 32 * 1024
+	}
+	digest, result := hashimotoLight(size, cache, header.HashNoNonce().Bytes(), header.Nonce.Uint64())
+	if !bytes.Equal(header.MixDigest[:], digest) {
+		return ErrInvalidMixDigest
+	}
+	target := new(big.Int).Div(maxUint256, header.Difficulty)
+	if new(big.Int).SetBytes(result).Cmp(target) > 0 {
+		return ErrInvalidPoW
+	}
+	return nil
+}
+
+// Prepare implements consensus.Engine, initializing the difficulty field of a
+// header to conform to the ethash protocol. The changes are done inline.
+func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header) error {
+	parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)
+	if parent == nil {
+		return ErrParentUnknown
+	}
+	header.Difficulty = CalcDifficulty(chain.Config(), header.Time.Uint64(),
+		parent.Time.Uint64(), parent.Number, parent.Difficulty)
+
+	return nil
+}
+
+// Finalize implements consensus.Engine, accumulating the block and uncle rewards,
+// setting the final state and assembling the block.
+func (ethash *Ethash) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
+	// Accumulate any block and uncle rewards and commit the final state root
+	AccumulateRewards(state, header, uncles)
+	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
+
+	// Header seems complete, assemble into a block and return
+	return types.NewBlock(header, txs, uncles, receipts), nil
+}
+
+// Some weird constants to avoid constant memory allocs for them.
+var (
+	big8  = big.NewInt(8)
+	big32 = big.NewInt(32)
+)
+
+// AccumulateRewards credits the coinbase of the given block with the mining
+// reward. The total reward consists of the static block reward and rewards for
+// included uncles. The coinbase of each uncle block is also rewarded.
+//
+// TODO (karalabe): Move the chain maker into this package and make this private!
+func AccumulateRewards(state *state.StateDB, header *types.Header, uncles []*types.Header) {
+	reward := new(big.Int).Set(blockReward)
+	r := new(big.Int)
+	for _, uncle := range uncles {
+		r.Add(uncle.Number, big8)
+		r.Sub(r, header.Number)
+		r.Mul(r, blockReward)
+		r.Div(r, big8)
+		state.AddBalance(uncle.Coinbase, r)
+
+		r.Div(blockReward, big32)
+		reward.Add(reward, r)
+	}
+	state.AddBalance(header.Coinbase, reward)
+}
diff --git a/consensus/ethash/consensus_test.go b/consensus/ethash/consensus_test.go
new file mode 100644
index 000000000..683c10be4
--- /dev/null
+++ b/consensus/ethash/consensus_test.go
@@ -0,0 +1,79 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethash
+
+import (
+	"encoding/json"
+	"math/big"
+	"os"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+type diffTest struct {
+	ParentTimestamp    uint64
+	ParentDifficulty   *big.Int
+	CurrentTimestamp   uint64
+	CurrentBlocknumber *big.Int
+	CurrentDifficulty  *big.Int
+}
+
+func (d *diffTest) UnmarshalJSON(b []byte) (err error) {
+	var ext struct {
+		ParentTimestamp    string
+		ParentDifficulty   string
+		CurrentTimestamp   string
+		CurrentBlocknumber string
+		CurrentDifficulty  string
+	}
+	if err := json.Unmarshal(b, &ext); err != nil {
+		return err
+	}
+
+	d.ParentTimestamp = math.MustParseUint64(ext.ParentTimestamp)
+	d.ParentDifficulty = math.MustParseBig256(ext.ParentDifficulty)
+	d.CurrentTimestamp = math.MustParseUint64(ext.CurrentTimestamp)
+	d.CurrentBlocknumber = math.MustParseBig256(ext.CurrentBlocknumber)
+	d.CurrentDifficulty = math.MustParseBig256(ext.CurrentDifficulty)
+
+	return nil
+}
+
+func TestCalcDifficulty(t *testing.T) {
+	file, err := os.Open("../../tests/files/BasicTests/difficulty.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer file.Close()
+
+	tests := make(map[string]diffTest)
+	err = json.NewDecoder(file).Decode(&tests)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
+	for name, test := range tests {
+		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
+		diff := CalcDifficulty(config, test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
+		if diff.Cmp(test.CurrentDifficulty) != 0 {
+			t.Error(name, "failed. Expected", test.CurrentDifficulty, "and calculated", diff)
+		}
+	}
+}
diff --git a/pow/ethash.go b/consensus/ethash/ethash.go
index 9adc38540..aa5b2d8a0 100644
--- a/pow/ethash.go
+++ b/consensus/ethash/ethash.go
@@ -14,10 +14,10 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package pow
+// Package ethash implements the ethash proof-of-work consensus engine.
+package ethash
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"math"
@@ -32,24 +32,20 @@ import (
 	"unsafe"
 
 	mmap "github.com/edsrzf/mmap-go"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/rpc"
 	metrics "github.com/rcrowley/go-metrics"
 )
 
-var (
-	ErrInvalidDumpMagic  = errors.New("invalid dump magic")
-	ErrNonceOutOfRange   = errors.New("nonce out of range")
-	ErrInvalidDifficulty = errors.New("non-positive difficulty")
-	ErrInvalidMixDigest  = errors.New("invalid mix digest")
-	ErrInvalidPoW        = errors.New("pow difficulty invalid")
-)
+var ErrInvalidDumpMagic = errors.New("invalid dump magic")
 
 var (
 	// maxUint256 is a big integer representing 2^256-1
 	maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
 
 	// sharedEthash is a full instance that can be shared between multiple users.
-	sharedEthash = NewFullEthash("", 3, 0, "", 1, 0)
+	sharedEthash = New("", 3, 0, "", 1, 0)
 
 	// algorithmRevision is the data structure version used for file naming.
 	algorithmRevision = 23
@@ -321,7 +317,8 @@ func MakeDataset(block uint64, dir string) {
 	d.release()
 }
 
-// Ethash is a PoW data struture implementing the ethash algorithm.
+// Ethash is a consensus engine based on proot-of-work implementing the ethash
+// algorithm.
 type Ethash struct {
 	cachedir     string // Data directory to store the verification caches
 	cachesinmem  int    // Number of caches to keep in memory
@@ -334,15 +331,26 @@ type Ethash struct {
 	fcache   *cache              // Pre-generated cache for the estimated future epoch
 	datasets map[uint64]*dataset // In memory datasets to avoid regenerating too often
 	fdataset *dataset            // Pre-generated dataset for the estimated future epoch
-	lock     sync.Mutex          // Ensures thread safety for the in-memory caches
 
+	// Mining related fields
+	rand     *rand.Rand    // Properly seeded random source for nonces
+	threads  int           // Number of threads to mine on if mining
+	update   chan struct{} // Notification channel to update mining parameters
 	hashrate metrics.Meter // Meter tracking the average hashrate
 
-	tester bool // Flag whether to use a smaller test dataset
+	// The fields below are hooks for testing
+	tester    bool          // Flag whether to use a smaller test dataset
+	shared    *Ethash       // Shared PoW verifier to avoid cache regeneration
+	fakeMode  bool          // Flag whether to disable PoW checking
+	fakeFull  bool          // Flag whether to disable all consensus rules
+	fakeFail  uint64        // Block number which fails PoW check even in fake mode
+	fakeDelay time.Duration // Time delay to sleep for before returning from verify
+
+	lock sync.Mutex // Ensures thread safety for the in-memory caches and mining fields
 }
 
-// NewFullEthash creates a full sized ethash PoW scheme.
-func NewFullEthash(cachedir string, cachesinmem, cachesondisk int, dagdir string, dagsinmem, dagsondisk int) PoW {
+// New creates a full sized ethash PoW scheme.
+func New(cachedir string, cachesinmem, cachesondisk int, dagdir string, dagsinmem, dagsondisk int) *Ethash {
 	if cachesinmem <= 0 {
 		log.Warn("One ethash cache must alwast be in memory", "requested", cachesinmem)
 		cachesinmem = 1
@@ -362,58 +370,55 @@ func NewFullEthash(cachedir string, cachesinmem, cachesondisk int, dagdir string
 		dagsondisk:   dagsondisk,
 		caches:       make(map[uint64]*cache),
 		datasets:     make(map[uint64]*dataset),
+		update:       make(chan struct{}),
 		hashrate:     metrics.NewMeter(),
 	}
 }
 
-// NewTestEthash creates a small sized ethash PoW scheme useful only for testing
+// NewTester creates a small sized ethash PoW scheme useful only for testing
 // purposes.
-func NewTestEthash() PoW {
+func NewTester() *Ethash {
 	return &Ethash{
 		cachesinmem: 1,
 		caches:      make(map[uint64]*cache),
 		datasets:    make(map[uint64]*dataset),
 		tester:      true,
+		update:      make(chan struct{}),
 		hashrate:    metrics.NewMeter(),
 	}
 }
 
-// NewSharedEthash creates a full sized ethash PoW shared between all requesters
-// running in the same process.
-func NewSharedEthash() PoW {
-	return sharedEthash
+// NewFaker creates a ethash consensus engine with a fake PoW scheme that accepts
+// all blocks' seal as valid, though they still have to conform to the Ethereum
+// consensus rules.
+func NewFaker() *Ethash {
+	return &Ethash{fakeMode: true}
 }
 
-// Verify implements PoW, checking whether the given block satisfies the PoW
-// difficulty requirements.
-func (ethash *Ethash) Verify(block Block) error {
-	// Sanity check that the block number is below the lookup table size (60M blocks)
-	number := block.NumberU64()
-	if number/epochLength >= uint64(len(cacheSizes)) {
-		// Go < 1.7 cannot calculate new cache/dataset sizes (no fast prime check)
-		return ErrNonceOutOfRange
-	}
-	// Ensure that we have a valid difficulty for the block
-	difficulty := block.Difficulty()
-	if difficulty.Sign() <= 0 {
-		return ErrInvalidDifficulty
-	}
-	// Recompute the digest and PoW value and verify against the block
-	cache := ethash.cache(number)
+// NewFakeFailer creates a ethash consensus engine with a fake PoW scheme that
+// accepts all blocks as valid apart from the single one specified, though they
+// still have to conform to the Ethereum consensus rules.
+func NewFakeFailer(fail uint64) *Ethash {
+	return &Ethash{fakeMode: true, fakeFail: fail}
+}
 
-	size := datasetSize(number)
-	if ethash.tester {
-		size = 32 * 1024
-	}
-	digest, result := hashimotoLight(size, cache, block.HashNoNonce().Bytes(), block.Nonce())
-	if !bytes.Equal(block.MixDigest().Bytes(), digest) {
-		return ErrInvalidMixDigest
-	}
-	target := new(big.Int).Div(maxUint256, difficulty)
-	if new(big.Int).SetBytes(result).Cmp(target) > 0 {
-		return ErrInvalidPoW
-	}
-	return nil
+// NewFakeDelayer creates a ethash consensus engine with a fake PoW scheme that
+// accepts all blocks as valid, but delays verifications by some time, though
+// they still have to conform to the Ethereum consensus rules.
+func NewFakeDelayer(delay time.Duration) *Ethash {
+	return &Ethash{fakeMode: true, fakeDelay: delay}
+}
+
+// NewFullFaker creates a ethash consensus engine with a full fake scheme that
+// accepts all blocks as valid, without checking any consensus rules whatsoever.
+func NewFullFaker() *Ethash {
+	return &Ethash{fakeMode: true, fakeFull: true}
+}
+
+// NewShared creates a full sized ethash PoW shared between all requesters running
+// in the same process.
+func NewShared() *Ethash {
+	return &Ethash{shared: sharedEthash}
 }
 
 // cache tries to retrieve a verification cache for the specified block number
@@ -477,43 +482,6 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
 	return current.cache
 }
 
-// Search implements PoW, attempting to find a nonce that satisfies the block's
-// difficulty requirements.
-func (ethash *Ethash) Search(block Block, stop <-chan struct{}) (uint64, []byte) {
-	var (
-		hash     = block.HashNoNonce().Bytes()
-		diff     = block.Difficulty()
-		target   = new(big.Int).Div(maxUint256, diff)
-		dataset  = ethash.dataset(block.NumberU64())
-		rand     = rand.New(rand.NewSource(time.Now().UnixNano()))
-		nonce    = uint64(rand.Int63())
-		attempts int64
-	)
-	// Start generating random nonces until we abort or find a good one
-	for {
-		select {
-		case <-stop:
-			// Mining terminated, update stats and abort
-			ethash.hashrate.Mark(attempts)
-			return 0, nil
-
-		default:
-			// We don't have to update hash rate on every nonce, so update after after 2^X nonces
-			attempts++
-			if (attempts % (1 << 15)) == 0 {
-				ethash.hashrate.Mark(attempts)
-				attempts = 0
-			}
-			// Compute the PoW value of this nonce
-			digest, result := hashimotoFull(dataset, hash, nonce)
-			if new(big.Int).SetBytes(result).Cmp(target) <= 0 {
-				return nonce, digest
-			}
-			nonce++
-		}
-	}
-}
-
 // dataset tries to retrieve a mining dataset for the specified block number
 // by first checking against a list of in-memory datasets, then against DAGs
 // stored on disk, and finally generating one if none can be found.
@@ -576,14 +544,44 @@ func (ethash *Ethash) dataset(block uint64) []uint32 {
 	return current.dataset
 }
 
+// Threads returns the number of mining threads currently enabled. This doesn't
+// necessarily mean that mining is running!
+func (ethash *Ethash) Threads() int {
+	ethash.lock.Lock()
+	defer ethash.lock.Unlock()
+
+	return ethash.threads
+}
+
+// SetThreads updates the number of mining threads currently enabled. Calling
+// this method does not start mining, only sets the thread count. If zero is
+// specified, the miner will use all cores of the machine.
+func (ethash *Ethash) SetThreads(threads int) {
+	ethash.lock.Lock()
+	defer ethash.lock.Unlock()
+
+	// Update the threads and ping any running seal to pull in any changes
+	ethash.threads = threads
+	select {
+	case ethash.update <- struct{}{}:
+	default:
+	}
+}
+
 // Hashrate implements PoW, returning the measured rate of the search invocations
 // per second over the last minute.
 func (ethash *Ethash) Hashrate() float64 {
 	return ethash.hashrate.Rate1()
 }
 
-// EthashSeedHash is the seed to use for generating a vrification cache and the
-// mining dataset.
-func EthashSeedHash(block uint64) []byte {
+// APIs implements consensus.Engine, returning the user facing RPC APIs. Currently
+// that is empty.
+func (ethash *Ethash) APIs(chain consensus.ChainReader) []rpc.API {
+	return nil
+}
+
+// SeedHash is the seed to use for generating a verification cache and the mining
+// dataset.
+func SeedHash(block uint64) []byte {
 	return seedHash(block)
 }
diff --git a/consensus/ethash/ethash_test.go b/consensus/ethash/ethash_test.go
new file mode 100644
index 000000000..b3a2f32f7
--- /dev/null
+++ b/consensus/ethash/ethash_test.go
@@ -0,0 +1,40 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethash
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// Tests that ethash works correctly in test mode.
+func TestTestMode(t *testing.T) {
+	head := &types.Header{Number: big.NewInt(1), Difficulty: big.NewInt(100)}
+
+	ethash := NewTester()
+	block, err := ethash.Seal(nil, types.NewBlockWithHeader(head), nil)
+	if err != nil {
+		t.Fatalf("failed to seal block: %v", err)
+	}
+	head.Nonce = types.EncodeNonce(block.Nonce())
+	head.MixDigest = block.MixDigest()
+	if err := ethash.VerifySeal(nil, head); err != nil {
+		t.Fatalf("unexpected verification error: %v", err)
+	}
+}
diff --git a/consensus/ethash/sealer.go b/consensus/ethash/sealer.go
new file mode 100644
index 000000000..9a000ed31
--- /dev/null
+++ b/consensus/ethash/sealer.go
@@ -0,0 +1,146 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethash
+
+import (
+	crand "crypto/rand"
+	"math"
+	"math/big"
+	"math/rand"
+	"runtime"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+// Seal implements consensus.Engine, attempting to find a nonce that satisfies
+// the block's difficulty requirements.
+func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
+	// If we're running a fake PoW, simply return a 0 nonce immediately
+	if ethash.fakeMode {
+		header := block.Header()
+		header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
+		return block.WithSeal(header), nil
+	}
+	// If we're running a shared PoW, delegate sealing to it
+	if ethash.shared != nil {
+		return ethash.shared.Seal(chain, block, stop)
+	}
+	// Create a runner and the multiple search threads it directs
+	abort := make(chan struct{})
+	found := make(chan *types.Block)
+
+	ethash.lock.Lock()
+	threads := ethash.threads
+	if ethash.rand == nil {
+		seed, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
+		if err != nil {
+			ethash.lock.Unlock()
+			return nil, err
+		}
+		ethash.rand = rand.New(rand.NewSource(seed.Int64()))
+	}
+	ethash.lock.Unlock()
+	if threads == 0 {
+		threads = runtime.NumCPU()
+	}
+	var pend sync.WaitGroup
+	for i := 0; i < threads; i++ {
+		pend.Add(1)
+		go func(id int, nonce uint64) {
+			defer pend.Done()
+			ethash.mine(block, id, nonce, abort, found)
+		}(i, uint64(ethash.rand.Int63()))
+	}
+	// Wait until sealing is terminated or a nonce is found
+	var result *types.Block
+	select {
+	case <-stop:
+		// Outside abort, stop all miner threads
+		close(abort)
+	case result = <-found:
+		// One of the threads found a block, abort all others
+		close(abort)
+	case <-ethash.update:
+		// Thread count was changed on user request, restart
+		close(abort)
+		pend.Wait()
+		return ethash.Seal(chain, block, stop)
+	}
+	// Wait for all miners to terminate and return the block
+	pend.Wait()
+	return result, nil
+}
+
+// mine is the actual proof-of-work miner that searches for a nonce starting from
+// seed that results in correct final block difficulty.
+func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan struct{}, found chan *types.Block) {
+	// Extract some data from the header
+	var (
+		header = block.Header()
+		hash   = header.HashNoNonce().Bytes()
+		target = new(big.Int).Div(maxUint256, header.Difficulty)
+
+		number  = header.Number.Uint64()
+		dataset = ethash.dataset(number)
+	)
+	// Start generating random nonces until we abort or find a good one
+	var (
+		attempts = int64(0)
+		nonce    = seed
+	)
+	logger := log.New("miner", id)
+	logger.Trace("Started ethash search for new nonces", "seed", seed)
+	for {
+		select {
+		case <-abort:
+			// Mining terminated, update stats and abort
+			logger.Trace("Ethash nonce search aborted", "attempts", nonce-seed)
+			ethash.hashrate.Mark(attempts)
+			return
+
+		default:
+			// We don't have to update hash rate on every nonce, so update after after 2^X nonces
+			attempts++
+			if (attempts % (1 << 15)) == 0 {
+				ethash.hashrate.Mark(attempts)
+				attempts = 0
+			}
+			// Compute the PoW value of this nonce
+			digest, result := hashimotoFull(dataset, hash, nonce)
+			if new(big.Int).SetBytes(result).Cmp(target) <= 0 {
+				// Correct nonce found, create a new header with it
+				header = types.CopyHeader(header)
+				header.Nonce = types.EncodeNonce(nonce)
+				header.MixDigest = common.BytesToHash(digest)
+
+				// Seal and return a block (if still needed)
+				select {
+				case found <- block.WithSeal(header):
+					logger.Trace("Ethash nonce found and reported", "attempts", nonce-seed, "nonce", nonce)
+				case <-abort:
+					logger.Trace("Ethash nonce found but discarded", "attempts", nonce-seed, "nonce", nonce)
+				}
+				return
+			}
+			nonce++
+		}
+	}
+}
diff --git a/pow/xor.go b/consensus/ethash/xor.go
index 558aeb469..90e232746 100644
--- a/pow/xor.go
+++ b/consensus/ethash/xor.go
@@ -4,7 +4,7 @@
 
 // Source: https://golang.org/src/crypto/cipher/xor.go
 
-package pow
+package ethash
 
 import (
 	"runtime"
diff --git a/consensus/misc/dao.go b/consensus/misc/dao.go
new file mode 100644
index 000000000..67d4adb44
--- /dev/null
+++ b/consensus/misc/dao.go
@@ -0,0 +1,85 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package misc
+
+import (
+	"bytes"
+	"errors"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+var (
+	// ErrBadProDAOExtra is returned if a header doens't support the DAO fork on a
+	// pro-fork client.
+	ErrBadProDAOExtra = errors.New("bad DAO pro-fork extra-data")
+
+	// ErrBadNoDAOExtra is returned if a header does support the DAO fork on a no-
+	// fork client.
+	ErrBadNoDAOExtra = errors.New("bad DAO no-fork extra-data")
+)
+
+// VerifyDAOHeaderExtraData validates the extra-data field of a block header to
+// ensure it conforms to DAO hard-fork rules.
+//
+// DAO hard-fork extension to the header validity:
+//   a) if the node is no-fork, do not accept blocks in the [fork, fork+10) range
+//      with the fork specific extra-data set
+//   b) if the node is pro-fork, require blocks in the specific range to have the
+//      unique extra-data set.
+func VerifyDAOHeaderExtraData(config *params.ChainConfig, header *types.Header) error {
+	// Short circuit validation if the node doesn't care about the DAO fork
+	if config.DAOForkBlock == nil {
+		return nil
+	}
+	// Make sure the block is within the fork's modified extra-data range
+	limit := new(big.Int).Add(config.DAOForkBlock, params.DAOForkExtraRange)
+	if header.Number.Cmp(config.DAOForkBlock) < 0 || header.Number.Cmp(limit) >= 0 {
+		return nil
+	}
+	// Depending whether we support or oppose the fork, validate the extra-data contents
+	if config.DAOForkSupport {
+		if !bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
+			return ErrBadProDAOExtra
+		}
+	} else {
+		if bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
+			return ErrBadNoDAOExtra
+		}
+	}
+	// All ok, header has the same extra-data we expect
+	return nil
+}
+
+// ApplyDAOHardFork modifies the state database according to the DAO hard-fork
+// rules, transferring all balances of a set of DAO accounts to a single refund
+// contract.
+func ApplyDAOHardFork(statedb *state.StateDB) {
+	// Retrieve the contract to refund balances into
+	if !statedb.Exist(params.DAORefundContract) {
+		statedb.CreateAccount(params.DAORefundContract)
+	}
+
+	// Move every DAO account and extra-balance account funds into the refund contract
+	for _, addr := range params.DAODrainList() {
+		statedb.AddBalance(params.DAORefundContract, statedb.GetBalance(addr))
+		statedb.SetBalance(addr, new(big.Int))
+	}
+}
diff --git a/consensus/misc/forks.go b/consensus/misc/forks.go
new file mode 100644
index 000000000..4a5e7c37e
--- /dev/null
+++ b/consensus/misc/forks.go
@@ -0,0 +1,43 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package misc
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+// VerifyForkHashes verifies that blocks conforming to network hard-forks do have
+// the correct hashes, to avoid clients going off on different chains. This is an
+// optional feature.
+func VerifyForkHashes(config *params.ChainConfig, header *types.Header, uncle bool) error {
+	// We don't care about uncles
+	if uncle {
+		return nil
+	}
+	// If the homestead reprice hash is set, validate it
+	if config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
+		if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
+			return fmt.Errorf("homestead gas reprice fork: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
+		}
+	}
+	// All ok, return
+	return nil
+}
diff --git a/core/bench_test.go b/core/bench_test.go
index a154ccbb1..20676fc97 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -25,13 +25,13 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func BenchmarkInsertChain_empty_memdb(b *testing.B) {
@@ -176,7 +176,7 @@ func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Time the insertion of the new chain.
 	// State and blocks are stored in the same DB.
 	evmux := new(event.TypeMux)
-	chainman, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	chainman, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	defer chainman.Stop()
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -286,7 +286,7 @@ func benchReadChain(b *testing.B, full bool, count uint64) {
 		if err != nil {
 			b.Fatalf("error opening database at %v: %v", dir, err)
 		}
-		chain, err := NewBlockChain(db, params.TestChainConfig, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+		chain, err := NewBlockChain(db, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 		if err != nil {
 			b.Fatalf("error creating chain: %v", err)
 		}
diff --git a/core/block_validator.go b/core/block_validator.go
index f93a9f40b..00457dd7a 100644
--- a/core/block_validator.go
+++ b/core/block_validator.go
@@ -19,22 +19,12 @@ package core
 import (
 	"fmt"
 	"math/big"
-	"time"
 
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
-	"gopkg.in/fatih/set.v0"
-)
-
-var (
-	ExpDiffPeriod = big.NewInt(100000)
-	big10         = big.NewInt(10)
-	bigMinus99    = big.NewInt(-99)
 )
 
 // BlockValidator is responsible for validating block headers, uncles and
@@ -44,30 +34,24 @@ var (
 type BlockValidator struct {
 	config *params.ChainConfig // Chain configuration options
 	bc     *BlockChain         // Canonical block chain
-	Pow    pow.PoW             // Proof of work used for validating
+	engine consensus.Engine    // Consensus engine used for validating
 }
 
 // NewBlockValidator returns a new block validator which is safe for re-use
-func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, pow pow.PoW) *BlockValidator {
+func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, engine consensus.Engine) *BlockValidator {
 	validator := &BlockValidator{
 		config: config,
-		Pow:    pow,
+		engine: engine,
 		bc:     blockchain,
 	}
 	return validator
 }
 
-// ValidateBlock validates the given block's header and uncles and verifies the
-// the block header's transaction and uncle roots.
-//
-// ValidateBlock does not validate the header's pow. The pow work validated
-// separately so we can process them in parallel.
-//
-// ValidateBlock also validates and makes sure that any previous state (or present)
-// state that might or might not be present is checked to make sure that fast
-// sync has done it's job proper. This prevents the block validator from accepting
-// false positives where a header is present but the state is not.
-func (v *BlockValidator) ValidateBlock(block *types.Block) error {
+// ValidateBody validates the given block's uncles and verifies the the block
+// header's transaction and uncle roots. The headers are assumed to be already
+// validated at this point.
+func (v *BlockValidator) ValidateBody(block *types.Block) error {
+	// Check whether the block's known, and if not, that it's linkable
 	if v.bc.HasBlock(block.Hash()) {
 		if _, err := state.New(block.Root(), v.bc.chainDb); err == nil {
 			return &KnownBlockError{block.Number(), block.Hash()}
@@ -80,30 +64,17 @@ func (v *BlockValidator) ValidateBlock(block *types.Block) error {
 	if _, err := state.New(parent.Root(), v.bc.chainDb); err != nil {
 		return ParentError(block.ParentHash())
 	}
-
+	// Header validity is known at this point, check the uncles and transactions
 	header := block.Header()
-	// validate the block header
-	if err := ValidateHeader(v.config, v.Pow, header, parent.Header(), false, false); err != nil {
+	if err := v.engine.VerifyUncles(v.bc, block); err != nil {
 		return err
 	}
-	// verify the uncles are correctly rewarded
-	if err := v.VerifyUncles(block, parent); err != nil {
-		return err
+	if hash := types.CalcUncleHash(block.Uncles()); hash != header.UncleHash {
+		return fmt.Errorf("uncle root hash mismatch: have %x, want %x", hash, header.UncleHash)
 	}
-
-	// Verify UncleHash before running other uncle validations
-	unclesSha := types.CalcUncleHash(block.Uncles())
-	if unclesSha != header.UncleHash {
-		return fmt.Errorf("invalid uncles root hash (remote: %x local: %x)", header.UncleHash, unclesSha)
-	}
-
-	// The transactions Trie's root (R = (Tr [[i, RLP(T1)], [i, RLP(T2)], ... [n, RLP(Tn)]]))
-	// can be used by light clients to make sure they've received the correct Txs
-	txSha := types.DeriveSha(block.Transactions())
-	if txSha != header.TxHash {
-		return fmt.Errorf("invalid transaction root hash (remote: %x local: %x)", header.TxHash, txSha)
+	if hash := types.DeriveSha(block.Transactions()); hash != header.TxHash {
+		return fmt.Errorf("transaction root hash mismatch: have %x, want %x", hash, header.TxHash)
 	}
-
 	return nil
 }
 
@@ -135,222 +106,6 @@ func (v *BlockValidator) ValidateState(block, parent *types.Block, statedb *stat
 	return nil
 }
 
-// VerifyUncles verifies the given block's uncles and applies the Ethereum
-// consensus rules to the various block headers included; it will return an
-// error if any of the included uncle headers were invalid. It returns an error
-// if the validation failed.
-func (v *BlockValidator) VerifyUncles(block, parent *types.Block) error {
-	// validate that there are at most 2 uncles included in this block
-	if len(block.Uncles()) > 2 {
-		return ValidationError("Block can only contain maximum 2 uncles (contained %v)", len(block.Uncles()))
-	}
-
-	uncles := set.New()
-	ancestors := make(map[common.Hash]*types.Block)
-	for _, ancestor := range v.bc.GetBlocksFromHash(block.ParentHash(), 7) {
-		ancestors[ancestor.Hash()] = ancestor
-		// Include ancestors uncles in the uncle set. Uncles must be unique.
-		for _, uncle := range ancestor.Uncles() {
-			uncles.Add(uncle.Hash())
-		}
-	}
-	ancestors[block.Hash()] = block
-	uncles.Add(block.Hash())
-
-	for i, uncle := range block.Uncles() {
-		hash := uncle.Hash()
-		if uncles.Has(hash) {
-			// Error not unique
-			return UncleError("uncle[%d](%x) not unique", i, hash[:4])
-		}
-		uncles.Add(hash)
-
-		if ancestors[hash] != nil {
-			branch := fmt.Sprintf("  O - %x\n  |\n", block.Hash())
-			for h := range ancestors {
-				branch += fmt.Sprintf("  O - %x\n  |\n", h)
-			}
-			log.Warn(branch)
-			return UncleError("uncle[%d](%x) is ancestor", i, hash[:4])
-		}
-
-		if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == parent.Hash() {
-			return UncleError("uncle[%d](%x)'s parent is not ancestor (%x)", i, hash[:4], uncle.ParentHash[0:4])
-		}
-
-		if err := ValidateHeader(v.config, v.Pow, uncle, ancestors[uncle.ParentHash].Header(), true, true); err != nil {
-			return ValidationError(fmt.Sprintf("uncle[%d](%x) header invalid: %v", i, hash[:4], err))
-		}
-	}
-
-	return nil
-}
-
-// ValidateHeader validates the given header and, depending on the pow arg,
-// checks the proof of work of the given header. Returns an error if the
-// validation failed.
-func (v *BlockValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
-	// Short circuit if the parent is missing.
-	if parent == nil {
-		return ParentError(header.ParentHash)
-	}
-	// Short circuit if the header's already known or its parent is missing
-	if v.bc.HasHeader(header.Hash()) {
-		return nil
-	}
-	return ValidateHeader(v.config, v.Pow, header, parent, checkPow, false)
-}
-
-// Validates a header. Returns an error if the header is invalid.
-//
-// See YP section 4.3.4. "Block Header Validity"
-func ValidateHeader(config *params.ChainConfig, pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
-	if uint64(len(header.Extra)) > params.MaximumExtraDataSize {
-		return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
-	}
-
-	if uncle {
-		if header.Time.Cmp(math.MaxBig256) == 1 {
-			return BlockTSTooBigErr
-		}
-	} else {
-		if header.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
-			return BlockFutureErr
-		}
-	}
-	if header.Time.Cmp(parent.Time) != 1 {
-		return BlockEqualTSErr
-	}
-
-	expd := CalcDifficulty(config, header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
-	if expd.Cmp(header.Difficulty) != 0 {
-		return fmt.Errorf("Difficulty check failed for header (remote: %v local: %v)", header.Difficulty, expd)
-	}
-
-	a := new(big.Int).Set(parent.GasLimit)
-	a = a.Sub(a, header.GasLimit)
-	a.Abs(a)
-	b := new(big.Int).Set(parent.GasLimit)
-	b = b.Div(b, params.GasLimitBoundDivisor)
-	if !(a.Cmp(b) < 0) || (header.GasLimit.Cmp(params.MinGasLimit) == -1) {
-		return fmt.Errorf("GasLimit check failed for header (remote: %v local_max: %v)", header.GasLimit, b)
-	}
-
-	num := new(big.Int).Set(parent.Number)
-	num.Sub(header.Number, num)
-	if num.Cmp(big.NewInt(1)) != 0 {
-		return BlockNumberErr
-	}
-
-	if checkPow {
-		// Verify the nonce of the header. Return an error if it's not valid
-		if err := pow.Verify(types.NewBlockWithHeader(header)); err != nil {
-			return &BlockNonceErr{header.Number, header.Hash(), header.Nonce.Uint64()}
-		}
-	}
-	// If all checks passed, validate the extra-data field for hard forks
-	if err := ValidateDAOHeaderExtraData(config, header); err != nil {
-		return err
-	}
-	if !uncle && config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
-		if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
-			return ValidationError("Homestead gas reprice fork hash mismatch: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
-		}
-	}
-	return nil
-}
-
-// CalcDifficulty is the difficulty adjustment algorithm. It returns
-// the difficulty that a new block should have when created at time
-// given the parent block's time and difficulty.
-func CalcDifficulty(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
-		return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
-	} else {
-		return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
-	}
-}
-
-func calcDifficultyHomestead(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
-	// algorithm:
-	// diff = (parent_diff +
-	//         (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
-	//        ) + 2^(periodCount - 2)
-
-	bigTime := new(big.Int).SetUint64(time)
-	bigParentTime := new(big.Int).SetUint64(parentTime)
-
-	// holds intermediate values to make the algo easier to read & audit
-	x := new(big.Int)
-	y := new(big.Int)
-
-	// 1 - (block_timestamp -parent_timestamp) // 10
-	x.Sub(bigTime, bigParentTime)
-	x.Div(x, big10)
-	x.Sub(common.Big1, x)
-
-	// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
-	if x.Cmp(bigMinus99) < 0 {
-		x.Set(bigMinus99)
-	}
-
-	// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
-	y.Div(parentDiff, params.DifficultyBoundDivisor)
-	x.Mul(y, x)
-	x.Add(parentDiff, x)
-
-	// minimum difficulty can ever be (before exponential factor)
-	if x.Cmp(params.MinimumDifficulty) < 0 {
-		x.Set(params.MinimumDifficulty)
-	}
-
-	// for the exponential factor
-	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, ExpDiffPeriod)
-
-	// the exponential factor, commonly referred to as "the bomb"
-	// diff = diff + 2^(periodCount - 2)
-	if periodCount.Cmp(common.Big1) > 0 {
-		y.Sub(periodCount, common.Big2)
-		y.Exp(common.Big2, y, nil)
-		x.Add(x, y)
-	}
-
-	return x
-}
-
-func calcDifficultyFrontier(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	diff := new(big.Int)
-	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
-	bigTime := new(big.Int)
-	bigParentTime := new(big.Int)
-
-	bigTime.SetUint64(time)
-	bigParentTime.SetUint64(parentTime)
-
-	if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
-		diff.Add(parentDiff, adjust)
-	} else {
-		diff.Sub(parentDiff, adjust)
-	}
-	if diff.Cmp(params.MinimumDifficulty) < 0 {
-		diff.Set(params.MinimumDifficulty)
-	}
-
-	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, ExpDiffPeriod)
-	if periodCount.Cmp(common.Big1) > 0 {
-		// diff = diff + 2^(periodCount - 2)
-		expDiff := periodCount.Sub(periodCount, common.Big2)
-		expDiff.Exp(common.Big2, expDiff, nil)
-		diff.Add(diff, expDiff)
-		diff = math.BigMax(diff, params.MinimumDifficulty)
-	}
-
-	return diff
-}
-
 // CalcGasLimit computes the gas limit of the next block after parent.
 // The result may be modified by the caller.
 // This is miner strategy, not consensus protocol.
diff --git a/core/block_validator_test.go b/core/block_validator_test.go
index a07dd9e51..abe1766b4 100644
--- a/core/block_validator_test.go
+++ b/core/block_validator_test.go
@@ -17,64 +17,179 @@
 package core
 
 import (
-	"math/big"
+	"runtime"
 	"testing"
+	"time"
 
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
-func testGenesis(account common.Address, balance *big.Int) *Genesis {
-	return &Genesis{
-		Config: params.TestChainConfig,
-		Alloc:  GenesisAlloc{account: {Balance: balance}},
+// Tests that simple header verification works, for both good and bad blocks.
+func TestHeaderVerification(t *testing.T) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
+	}
+	// Run the header checker for blocks one-by-one, checking for both valid and invalid nonces
+	chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
+
+	for i := 0; i < len(blocks); i++ {
+		for j, valid := range []bool{true, false} {
+			var results <-chan error
+
+			if valid {
+				engine := ethash.NewFaker()
+				_, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
+			} else {
+				engine := ethash.NewFakeFailer(headers[i].Number.Uint64())
+				_, results = engine.VerifyHeaders(chain, []*types.Header{headers[i]}, []bool{true})
+			}
+			// Wait for the verification result
+			select {
+			case result := <-results:
+				if (result == nil) != valid {
+					t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, result, valid)
+				}
+			case <-time.After(time.Second):
+				t.Fatalf("test %d.%d: verification timeout", i, j)
+			}
+			// Make sure no more data is returned
+			select {
+			case result := <-results:
+				t.Fatalf("test %d.%d: unexpected result returned: %v", i, j, result)
+			case <-time.After(25 * time.Millisecond):
+			}
+		}
+		chain.InsertChain(blocks[i : i+1])
 	}
 }
 
-func TestNumber(t *testing.T) {
-	chain := newTestBlockChain()
-	statedb, _ := state.New(chain.Genesis().Root(), chain.chainDb)
-	header := makeHeader(chain.config, chain.Genesis(), statedb)
-	header.Number = big.NewInt(3)
-	err := ValidateHeader(chain.config, pow.FakePow{}, header, chain.Genesis().Header(), false, false)
-	if err != BlockNumberErr {
-		t.Errorf("expected block number error, got %q", err)
+// Tests that concurrent header verification works, for both good and bad blocks.
+func TestHeaderConcurrentVerification2(t *testing.T)  { testHeaderConcurrentVerification(t, 2) }
+func TestHeaderConcurrentVerification8(t *testing.T)  { testHeaderConcurrentVerification(t, 8) }
+func TestHeaderConcurrentVerification32(t *testing.T) { testHeaderConcurrentVerification(t, 32) }
+
+func testHeaderConcurrentVerification(t *testing.T, threads int) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	seals := make([]bool, len(blocks))
+
+	for i, block := range blocks {
+		headers[i] = block.Header()
+		seals[i] = true
 	}
+	// Set the number of threads to verify on
+	old := runtime.GOMAXPROCS(threads)
+	defer runtime.GOMAXPROCS(old)
+
+	// Run the header checker for the entire block chain at once both for a valid and
+	// also an invalid chain (enough if one arbitrary block is invalid).
+	for i, valid := range []bool{true, false} {
+		var results <-chan error
+
+		if valid {
+			chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
+			_, results = chain.engine.VerifyHeaders(chain, headers, seals)
+		} else {
+			chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFakeFailer(uint64(len(headers)-1)), new(event.TypeMux), vm.Config{})
+			_, results = chain.engine.VerifyHeaders(chain, headers, seals)
+		}
+		// Wait for all the verification results
+		checks := make(map[int]error)
+		for j := 0; j < len(blocks); j++ {
+			select {
+			case result := <-results:
+				checks[j] = result
 
-	header = makeHeader(chain.config, chain.Genesis(), statedb)
-	err = ValidateHeader(chain.config, pow.FakePow{}, header, chain.Genesis().Header(), false, false)
-	if err == BlockNumberErr {
-		t.Errorf("didn't expect block number error")
+			case <-time.After(time.Second):
+				t.Fatalf("test %d.%d: verification timeout", i, j)
+			}
+		}
+		// Check nonce check validity
+		for j := 0; j < len(blocks); j++ {
+			want := valid || (j < len(blocks)-2) // We chose the last-but-one nonce in the chain to fail
+			if (checks[j] == nil) != want {
+				t.Errorf("test %d.%d: validity mismatch: have %v, want %v", i, j, checks[j], want)
+			}
+			if !want {
+				// A few blocks after the first error may pass verification due to concurrent
+				// workers. We don't care about those in this test, just that the correct block
+				// errors out.
+				break
+			}
+		}
+		// Make sure no more data is returned
+		select {
+		case result := <-results:
+			t.Fatalf("test %d: unexpected result returned: %v", i, result)
+		case <-time.After(25 * time.Millisecond):
+		}
 	}
 }
 
-func TestPutReceipt(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-
-	var addr common.Address
-	addr[0] = 1
-	var hash common.Hash
-	hash[0] = 2
-
-	receipt := new(types.Receipt)
-	receipt.Logs = []*types.Log{{
-		Address:     addr,
-		Topics:      []common.Hash{hash},
-		Data:        []byte("hi"),
-		BlockNumber: 42,
-		TxHash:      hash,
-		TxIndex:     0,
-		BlockHash:   hash,
-		Index:       0,
-	}}
-
-	WriteReceipts(db, types.Receipts{receipt})
-	receipt = GetReceipt(db, common.Hash{})
-	if receipt == nil {
-		t.Error("expected to get 1 receipt, got none.")
+// Tests that aborting a header validation indeed prevents further checks from being
+// run, as well as checks that no left-over goroutines are leaked.
+func TestHeaderConcurrentAbortion2(t *testing.T)  { testHeaderConcurrentAbortion(t, 2) }
+func TestHeaderConcurrentAbortion8(t *testing.T)  { testHeaderConcurrentAbortion(t, 8) }
+func TestHeaderConcurrentAbortion32(t *testing.T) { testHeaderConcurrentAbortion(t, 32) }
+
+func testHeaderConcurrentAbortion(t *testing.T, threads int) {
+	// Create a simple chain to verify
+	var (
+		testdb, _ = ethdb.NewMemDatabase()
+		gspec     = &Genesis{Config: params.TestChainConfig}
+		genesis   = gspec.MustCommit(testdb)
+		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 1024, nil)
+	)
+	headers := make([]*types.Header, len(blocks))
+	seals := make([]bool, len(blocks))
+
+	for i, block := range blocks {
+		headers[i] = block.Header()
+		seals[i] = true
+	}
+	// Set the number of threads to verify on
+	old := runtime.GOMAXPROCS(threads)
+	defer runtime.GOMAXPROCS(old)
+
+	// Start the verifications and immediately abort
+	chain, _ := NewBlockChain(testdb, params.TestChainConfig, ethash.NewFakeDelayer(time.Millisecond), new(event.TypeMux), vm.Config{})
+	abort, results := chain.engine.VerifyHeaders(chain, headers, seals)
+	close(abort)
+
+	// Deplete the results channel
+	verified := 0
+	for depleted := false; !depleted; {
+		select {
+		case result := <-results:
+			if result != nil {
+				t.Errorf("header %d: validation failed: %v", verified, result)
+			}
+			verified++
+		case <-time.After(50 * time.Millisecond):
+			depleted = true
+		}
+	}
+	// Check that abortion was honored by not processing too many POWs
+	if verified > 2*threads {
+		t.Errorf("verification count too large: have %d, want below %d", verified, 2*threads)
 	}
 }
diff --git a/core/blockchain.go b/core/blockchain.go
index a57832df0..4793431d8 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -30,6 +30,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 	"github.com/hashicorp/golang-lru"
@@ -104,7 +104,7 @@ type BlockChain struct {
 	procInterrupt int32          // interrupt signaler for block processing
 	wg            sync.WaitGroup // chain processing wait group for shutting down
 
-	pow       pow.PoW
+	engine    consensus.Engine
 	processor Processor // block processor interface
 	validator Validator // block and state validator interface
 	vmConfig  vm.Config
@@ -115,7 +115,7 @@ type BlockChain struct {
 // NewBlockChain returns a fully initialised block chain using information
 // available in the database. It initialiser the default Ethereum Validator and
 // Processor.
-func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, pow pow.PoW, mux *event.TypeMux, vmConfig vm.Config) (*BlockChain, error) {
+func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, engine consensus.Engine, mux *event.TypeMux, vmConfig vm.Config) (*BlockChain, error) {
 	bodyCache, _ := lru.New(bodyCacheLimit)
 	bodyRLPCache, _ := lru.New(bodyCacheLimit)
 	blockCache, _ := lru.New(blockCacheLimit)
@@ -131,25 +131,22 @@ func NewBlockChain(chainDb ethdb.Database, config *params.ChainConfig, pow pow.P
 		bodyRLPCache: bodyRLPCache,
 		blockCache:   blockCache,
 		futureBlocks: futureBlocks,
-		pow:          pow,
+		engine:       engine,
 		vmConfig:     vmConfig,
 		badBlocks:    badBlocks,
 	}
-	bc.SetValidator(NewBlockValidator(config, bc, pow))
-	bc.SetProcessor(NewStateProcessor(config, bc))
+	bc.SetValidator(NewBlockValidator(config, bc, engine))
+	bc.SetProcessor(NewStateProcessor(config, bc, engine))
 
-	gv := func() HeaderValidator { return bc.Validator() }
 	var err error
-	bc.hc, err = NewHeaderChain(chainDb, config, gv, bc.getProcInterrupt)
+	bc.hc, err = NewHeaderChain(chainDb, config, engine, bc.getProcInterrupt)
 	if err != nil {
 		return nil, err
 	}
-
 	bc.genesisBlock = bc.GetBlockByNumber(0)
 	if bc.genesisBlock == nil {
 		return nil, ErrNoGenesis
 	}
-
 	if err := bc.loadLastState(); err != nil {
 		return nil, err
 	}
@@ -233,9 +230,6 @@ func (self *BlockChain) loadLastState() error {
 	log.Info("Loaded most recent local full block", "number", self.currentBlock.Number(), "hash", self.currentBlock.Hash(), "td", blockTd)
 	log.Info("Loaded most recent local fast block", "number", self.currentFastBlock.Number(), "hash", self.currentFastBlock.Hash(), "td", fastTd)
 
-	// Try to be smart and issue a pow verification for the head to pre-generate caches
-	go self.pow.Verify(types.NewBlockWithHeader(currentHeader))
-
 	return nil
 }
 
@@ -383,9 +377,6 @@ func (self *BlockChain) Processor() Processor {
 	return self.processor
 }
 
-// AuxValidator returns the auxiliary validator (Proof of work atm)
-func (self *BlockChain) AuxValidator() pow.PoW { return self.pow }
-
 // State returns a new mutable state based on the current HEAD block.
 func (self *BlockChain) State() (*state.StateDB, error) {
 	return self.StateAt(self.CurrentBlock().Root())
@@ -906,38 +897,38 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 		stats         = insertStats{startTime: mclock.Now()}
 		events        = make([]interface{}, 0, len(chain))
 		coalescedLogs []*types.Log
-		nonceChecked  = make([]bool, len(chain))
 	)
+	// Start the parallel header verifier
+	headers := make([]*types.Header, len(chain))
+	seals := make([]bool, len(chain))
 
-	// Start the parallel nonce verifier.
-	nonceAbort, nonceResults := verifyNoncesFromBlocks(self.pow, chain)
-	defer close(nonceAbort)
+	for i, block := range chain {
+		headers[i] = block.Header()
+		seals[i] = true
+	}
+	abort, results := self.engine.VerifyHeaders(self, headers, seals)
+	defer close(abort)
 
+	// Iterate over the blocks and insert when the verifier permits
 	for i, block := range chain {
+		// If the chain is terminating, stop processing blocks
 		if atomic.LoadInt32(&self.procInterrupt) == 1 {
 			log.Debug("Premature abort during blocks processing")
 			break
 		}
-		bstart := time.Now()
-		// Wait for block i's nonce to be verified before processing
-		// its state transition.
-		for !nonceChecked[i] {
-			r := <-nonceResults
-			nonceChecked[r.index] = true
-			if !r.valid {
-				invalid := chain[r.index]
-				return r.index, &BlockNonceErr{Hash: invalid.Hash(), Number: invalid.Number(), Nonce: invalid.Nonce()}
-			}
-		}
-
+		// If the header is a banned one, straight out abort
 		if BadHashes[block.Hash()] {
 			err := BadHashError(block.Hash())
 			self.reportBlock(block, nil, err)
 			return i, err
 		}
-		// Stage 1 validation of the block using the chain's validator
-		// interface.
-		err := self.Validator().ValidateBlock(block)
+		// Wait for the block's verification to complete
+		bstart := time.Now()
+
+		err := <-results
+		if err == nil {
+			err = self.Validator().ValidateBody(block)
+		}
 		if err != nil {
 			if IsKnownBlockErr(err) {
 				stats.ignored++
@@ -952,7 +943,6 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 				if block.Time().Cmp(max) == 1 {
 					return i, fmt.Errorf("%v: BlockFutureErr, %v > %v", BlockFutureErr, block.Time(), max)
 				}
-
 				self.futureBlocks.Add(block.Hash(), block)
 				stats.queued++
 				continue
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index 3da133a9e..b2fb226db 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -31,18 +32,21 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // newTestBlockChain creates a blockchain without validation.
-func newTestBlockChain() *BlockChain {
+func newTestBlockChain(fake bool) *BlockChain {
 	db, _ := ethdb.NewMemDatabase()
 	gspec := &Genesis{
 		Config:     params.TestChainConfig,
 		Difficulty: big.NewInt(1),
 	}
 	gspec.MustCommit(db)
-	blockchain, err := NewBlockChain(db, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	engine := ethash.NewFullFaker()
+	if !fake {
+		engine = ethash.NewTester()
+	}
+	blockchain, err := NewBlockChain(db, gspec.Config, engine, new(event.TypeMux), vm.Config{})
 	if err != nil {
 		panic(err)
 	}
@@ -117,7 +121,10 @@ func printChain(bc *BlockChain) {
 func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 	for _, block := range chain {
 		// Try and process the block
-		err := blockchain.Validator().ValidateBlock(block)
+		err := blockchain.engine.VerifyHeader(blockchain, block.Header(), true)
+		if err == nil {
+			err = blockchain.validator.ValidateBody(block)
+		}
 		if err != nil {
 			if IsKnownBlockErr(err) {
 				continue
@@ -133,7 +140,7 @@ func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 			blockchain.reportBlock(block, receipts, err)
 			return err
 		}
-		err = blockchain.Validator().ValidateState(block, blockchain.GetBlockByHash(block.ParentHash()), statedb, receipts, usedGas)
+		err = blockchain.validator.ValidateState(block, blockchain.GetBlockByHash(block.ParentHash()), statedb, receipts, usedGas)
 		if err != nil {
 			blockchain.reportBlock(block, receipts, err)
 			return err
@@ -152,7 +159,7 @@ func testBlockChainImport(chain types.Blocks, blockchain *BlockChain) error {
 func testHeaderChainImport(chain []*types.Header, blockchain *BlockChain) error {
 	for _, header := range chain {
 		// Try and validate the header
-		if err := blockchain.Validator().ValidateHeader(header, blockchain.GetHeaderByHash(header.ParentHash), false); err != nil {
+		if err := blockchain.engine.VerifyHeader(blockchain, header, false); err != nil {
 			return err
 		}
 		// Manually insert the header into the database, but don't reorganise (allows subsequent testing)
@@ -174,7 +181,7 @@ func insertChain(done chan bool, blockchain *BlockChain, chain types.Blocks, t *
 }
 
 func TestLastBlock(t *testing.T) {
-	bchain := newTestBlockChain()
+	bchain := newTestBlockChain(false)
 	block := makeBlockChain(bchain.CurrentBlock(), 1, bchain.chainDb, 0)[0]
 	bchain.insert(block)
 	if block.Hash() != GetHeadBlockHash(bchain.chainDb) {
@@ -318,8 +325,7 @@ func testBrokenChain(t *testing.T, full bool) {
 
 type bproc struct{}
 
-func (bproc) ValidateBlock(*types.Block) error                        { return nil }
-func (bproc) ValidateHeader(*types.Header, *types.Header, bool) error { return nil }
+func (bproc) ValidateBody(*types.Block) error { return nil }
 func (bproc) ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error {
 	return nil
 }
@@ -378,7 +384,7 @@ func testReorgShort(t *testing.T, full bool) {
 }
 
 func testReorg(t *testing.T, first, second []int, td int64, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Insert an easy and a difficult chain afterwards
 	if full {
@@ -422,7 +428,7 @@ func TestBadHeaderHashes(t *testing.T) { testBadHashes(t, false) }
 func TestBadBlockHashes(t *testing.T)  { testBadHashes(t, true) }
 
 func testBadHashes(t *testing.T, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Create a chain, ban a hash and try to import
 	var err error
@@ -446,7 +452,7 @@ func TestReorgBadHeaderHashes(t *testing.T) { testReorgBadHashes(t, false) }
 func TestReorgBadBlockHashes(t *testing.T)  { testReorgBadHashes(t, true) }
 
 func testReorgBadHashes(t *testing.T, full bool) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(true)
 
 	// Create a chain, import and ban afterwards
 	headers := makeHeaderChainWithDiff(bc.genesisBlock, []int{1, 2, 3, 4}, 10)
@@ -473,7 +479,7 @@ func testReorgBadHashes(t *testing.T, full bool) {
 	}
 
 	// Create a new BlockChain and check that it rolled back the state.
-	ncm, err := NewBlockChain(bc.chainDb, bc.config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	ncm, err := NewBlockChain(bc.chainDb, bc.config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if err != nil {
 		t.Fatalf("failed to create new chain manager: %v", err)
 	}
@@ -504,46 +510,34 @@ func testInsertNonceError(t *testing.T, full bool) {
 		}
 		// Create and insert a chain with a failing nonce
 		var (
-			failAt   int
-			failRes  int
-			failNum  uint64
-			failHash common.Hash
+			failAt  int
+			failRes int
+			failNum uint64
 		)
 		if full {
 			blocks := makeBlockChain(blockchain.CurrentBlock(), i, db, 0)
 
 			failAt = rand.Int() % len(blocks)
 			failNum = blocks[failAt].NumberU64()
-			failHash = blocks[failAt].Hash()
-
-			blockchain.pow = failPow{failNum}
 
+			blockchain.engine = ethash.NewFakeFailer(failNum)
 			failRes, err = blockchain.InsertChain(blocks)
 		} else {
 			headers := makeHeaderChain(blockchain.CurrentHeader(), i, db, 0)
 
 			failAt = rand.Int() % len(headers)
 			failNum = headers[failAt].Number.Uint64()
-			failHash = headers[failAt].Hash()
-
-			blockchain.pow = failPow{failNum}
-			blockchain.validator = NewBlockValidator(params.TestChainConfig, blockchain, failPow{failNum})
 
+			blockchain.engine = ethash.NewFakeFailer(failNum)
+			blockchain.hc.engine = blockchain.engine
 			failRes, err = blockchain.InsertHeaderChain(headers, 1)
 		}
 		// Check that the returned error indicates the nonce failure.
 		if failRes != failAt {
 			t.Errorf("test %d: failure index mismatch: have %d, want %d", i, failRes, failAt)
 		}
-		if !IsBlockNonceErr(err) {
-			t.Fatalf("test %d: error mismatch: have %v, want nonce error %T", i, err, err)
-		}
-		nerr := err.(*BlockNonceErr)
-		if nerr.Number.Uint64() != failNum {
-			t.Errorf("test %d: number mismatch: have %v, want %v", i, nerr.Number, failNum)
-		}
-		if nerr.Hash != failHash {
-			t.Errorf("test %d: hash mismatch: have %x, want %x", i, nerr.Hash[:4], failHash[:4])
+		if err != ethash.ErrInvalidPoW {
+			t.Fatalf("test %d: error mismatch: have %v, want %v", i, err, ethash.ErrInvalidPoW)
 		}
 		// Check that all no blocks after the failing block have been inserted.
 		for j := 0; j < i-failAt; j++ {
@@ -569,9 +563,12 @@ func TestFastVsFullChains(t *testing.T) {
 		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address  = crypto.PubkeyToAddress(key.PublicKey)
 		funds    = big.NewInt(1000000000)
-		gspec    = testGenesis(address, funds)
-		genesis  = gspec.MustCommit(gendb)
-		signer   = types.NewEIP155Signer(gspec.Config.ChainId)
+		gspec    = &Genesis{
+			Config: params.TestChainConfig,
+			Alloc:  GenesisAlloc{address: {Balance: funds}},
+		}
+		genesis = gspec.MustCommit(gendb)
+		signer  = types.NewEIP155Signer(gspec.Config.ChainId)
 	)
 	blocks, receipts := GenerateChain(gspec.Config, genesis, gendb, 1024, func(i int, block *BlockGen) {
 		block.SetCoinbase(common.Address{0x00})
@@ -594,7 +591,7 @@ func TestFastVsFullChains(t *testing.T) {
 	// Import the chain as an archive node for the comparison baseline
 	archiveDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
-	archive, _ := NewBlockChain(archiveDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	archive, _ := NewBlockChain(archiveDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	if n, err := archive.InsertChain(blocks); err != nil {
 		t.Fatalf("failed to process block %d: %v", n, err)
@@ -603,7 +600,7 @@ func TestFastVsFullChains(t *testing.T) {
 	// Fast import the chain as a non-archive node to test
 	fastDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
-	fast, _ := NewBlockChain(fastDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	fast, _ := NewBlockChain(fastDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	headers := make([]*types.Header, len(blocks))
 	for i, block := range blocks {
@@ -680,8 +677,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	archiveDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 
-	archive, _ := NewBlockChain(archiveDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
-
+	archive, _ := NewBlockChain(archiveDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if n, err := archive.InsertChain(blocks); err != nil {
 		t.Fatalf("failed to process block %d: %v", n, err)
 	}
@@ -692,7 +688,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Import the chain as a non-archive node and ensure all pointers are updated
 	fastDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
-	fast, _ := NewBlockChain(fastDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	fast, _ := NewBlockChain(fastDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	headers := make([]*types.Header, len(blocks))
 	for i, block := range blocks {
@@ -711,8 +707,8 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Import the chain as a light node and ensure all pointers are updated
 	lightDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(lightDb)
-	light, _ := NewBlockChain(lightDb, gspec.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
 
+	light, _ := NewBlockChain(lightDb, gspec.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	if n, err := light.InsertHeaderChain(headers, 1); err != nil {
 		t.Fatalf("failed to insert header %d: %v", n, err)
 	}
@@ -780,7 +776,7 @@ func TestChainTxReorgs(t *testing.T) {
 	})
 	// Import the chain. This runs all block validation rules.
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	if i, err := blockchain.InsertChain(chain); err != nil {
 		t.Fatalf("failed to insert original chain[%d]: %v", i, err)
 	}
@@ -851,7 +847,7 @@ func TestLogReorgs(t *testing.T) {
 	)
 
 	var evmux event.TypeMux
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, &evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), &evmux, vm.Config{})
 
 	subs := evmux.Subscribe(RemovedLogsEvent{})
 	chain, _ := GenerateChain(params.TestChainConfig, genesis, db, 2, func(i int, gen *BlockGen) {
@@ -883,13 +879,16 @@ func TestReorgSideEvent(t *testing.T) {
 		db, _   = ethdb.NewMemDatabase()
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		gspec   = testGenesis(addr1, big.NewInt(10000000000000))
+		gspec   = &Genesis{
+			Config: params.TestChainConfig,
+			Alloc:  GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}},
+		}
 		genesis = gspec.MustCommit(db)
 		signer  = types.NewEIP155Signer(gspec.Config.ChainId)
 	)
 
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 
 	chain, _ := GenerateChain(gspec.Config, genesis, db, 3, func(i int, gen *BlockGen) {})
 	if _, err := blockchain.InsertChain(chain); err != nil {
@@ -959,7 +958,7 @@ done:
 
 // Tests if the canonical block can be fetched from the database during chain insertion.
 func TestCanonicalBlockRetrieval(t *testing.T) {
-	bc := newTestBlockChain()
+	bc := newTestBlockChain(false)
 	chain, _ := GenerateChain(bc.config, bc.genesisBlock, bc.chainDb, 10, func(i int, gen *BlockGen) {})
 
 	for i := range chain {
@@ -1004,7 +1003,7 @@ func TestEIP155Transition(t *testing.T) {
 		mux     event.TypeMux
 	)
 
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, &mux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), &mux, vm.Config{})
 	blocks, _ := GenerateChain(gspec.Config, genesis, db, 4, func(i int, block *BlockGen) {
 		var (
 			tx      *types.Transaction
@@ -1110,7 +1109,7 @@ func TestEIP161AccountRemoval(t *testing.T) {
 		}
 		genesis       = gspec.MustCommit(db)
 		mux           event.TypeMux
-		blockchain, _ = NewBlockChain(db, gspec.Config, pow.FakePow{}, &mux, vm.Config{})
+		blockchain, _ = NewBlockChain(db, gspec.Config, ethash.NewFaker(), &mux, vm.Config{})
 	)
 	blocks, _ := GenerateChain(gspec.Config, genesis, db, 3, func(i int, block *BlockGen) {
 		var (
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 5bf1ece25..c47c719f6 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -21,13 +21,14 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // So we can deterministically seed different blockchains
@@ -141,7 +142,7 @@ func (b *BlockGen) OffsetTime(seconds int64) {
 	if b.header.Time.Cmp(b.parent.Header().Time) <= 0 {
 		panic("block time out of range")
 	}
-	b.header.Difficulty = CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
+	b.header.Difficulty = ethash.CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
 }
 
 // GenerateChain creates a chain of n blocks. The first block's
@@ -173,13 +174,13 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, db ethdb.Dat
 			}
 		}
 		if config.DAOForkSupport && config.DAOForkBlock != nil && config.DAOForkBlock.Cmp(h.Number) == 0 {
-			ApplyDAOHardFork(statedb)
+			misc.ApplyDAOHardFork(statedb)
 		}
 		// Execute any user modifications to the block and finalize it
 		if gen != nil {
 			gen(i, b)
 		}
-		AccumulateRewards(statedb, h, b.uncles)
+		ethash.AccumulateRewards(statedb, h, b.uncles)
 		root, err := statedb.Commit(config.IsEIP158(h.Number))
 		if err != nil {
 			panic(fmt.Sprintf("state write error: %v", err))
@@ -212,7 +213,7 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
 		Root:       state.IntermediateRoot(config.IsEIP158(parent.Number())),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
-		Difficulty: CalcDifficulty(config, time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
+		Difficulty: ethash.CalcDifficulty(config, time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
 		GasLimit:   CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
 		Number:     new(big.Int).Add(parent.Number(), common.Big1),
@@ -229,7 +230,7 @@ func newCanonical(n int, full bool) (ethdb.Database, *BlockChain, error) {
 	db, _ := ethdb.NewMemDatabase()
 	genesis := gspec.MustCommit(db)
 
-	blockchain, _ := NewBlockChain(db, params.AllProtocolChanges, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+	blockchain, _ := NewBlockChain(db, params.AllProtocolChanges, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	// Create and inject the requested chain
 	if n == 0 {
 		return db, blockchain, nil
diff --git a/core/chain_makers_test.go b/core/chain_makers_test.go
index a8f77cdf3..3a7c62396 100644
--- a/core/chain_makers_test.go
+++ b/core/chain_makers_test.go
@@ -20,13 +20,13 @@ import (
 	"fmt"
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func ExampleGenerateChain() {
@@ -81,7 +81,7 @@ func ExampleGenerateChain() {
 
 	// Import the chain. This runs all block validation rules.
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, gspec.Config, pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, gspec.Config, ethash.NewFaker(), evmux, vm.Config{})
 	if i, err := blockchain.InsertChain(chain); err != nil {
 		fmt.Printf("insert error (block %d): %v\n", chain[i].NumberU64(), err)
 		return
diff --git a/core/chain_pow.go b/core/chain_pow.go
deleted file mode 100644
index e5ccd87e2..000000000
--- a/core/chain_pow.go
+++ /dev/null
@@ -1,87 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package core
-
-import (
-	"runtime"
-
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/pow"
-)
-
-// nonceCheckResult contains the result of a nonce verification.
-type nonceCheckResult struct {
-	index int  // Index of the item verified from an input array
-	valid bool // Result of the nonce verification
-}
-
-// verifyNoncesFromHeaders starts a concurrent header nonce verification,
-// returning a quit channel to abort the operations and a results channel
-// to retrieve the async verifications.
-func verifyNoncesFromHeaders(checker pow.PoW, headers []*types.Header) (chan<- struct{}, <-chan nonceCheckResult) {
-	items := make([]pow.Block, len(headers))
-	for i, header := range headers {
-		items[i] = types.NewBlockWithHeader(header)
-	}
-	return verifyNonces(checker, items)
-}
-
-// verifyNoncesFromBlocks starts a concurrent block nonce verification,
-// returning a quit channel to abort the operations and a results channel
-// to retrieve the async verifications.
-func verifyNoncesFromBlocks(checker pow.PoW, blocks []*types.Block) (chan<- struct{}, <-chan nonceCheckResult) {
-	items := make([]pow.Block, len(blocks))
-	for i, block := range blocks {
-		items[i] = block
-	}
-	return verifyNonces(checker, items)
-}
-
-// verifyNonces starts a concurrent nonce verification, returning a quit channel
-// to abort the operations and a results channel to retrieve the async checks.
-func verifyNonces(checker pow.PoW, items []pow.Block) (chan<- struct{}, <-chan nonceCheckResult) {
-	// Spawn as many workers as allowed threads
-	workers := runtime.GOMAXPROCS(0)
-	if len(items) < workers {
-		workers = len(items)
-	}
-	// Create a task channel and spawn the verifiers
-	tasks := make(chan int, workers)
-	results := make(chan nonceCheckResult, len(items)) // Buffered to make sure all workers stop
-	for i := 0; i < workers; i++ {
-		go func() {
-			for index := range tasks {
-				results <- nonceCheckResult{index: index, valid: checker.Verify(items[index]) == nil}
-			}
-		}()
-	}
-	// Feed item indices to the workers until done or aborted
-	abort := make(chan struct{})
-	go func() {
-		defer close(tasks)
-
-		for i := range items {
-			select {
-			case tasks <- i:
-				continue
-			case <-abort:
-				return
-			}
-		}
-	}()
-	return abort, results
-}
diff --git a/core/chain_pow_test.go b/core/chain_pow_test.go
deleted file mode 100644
index 311ca128e..000000000
--- a/core/chain_pow_test.go
+++ /dev/null
@@ -1,238 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package core
-
-import (
-	"errors"
-	"math/big"
-	"runtime"
-	"testing"
-	"time"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/ethdb"
-	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
-)
-
-// failPow is a non-validating proof of work implementation, that returns true
-// from Verify for all but one block.
-type failPow struct {
-	failing uint64
-}
-
-func (pow failPow) Search(pow.Block, <-chan struct{}) (uint64, []byte) {
-	return 0, nil
-}
-func (pow failPow) Verify(block pow.Block) error {
-	if block.NumberU64() == pow.failing {
-		return errors.New("failed")
-	}
-	return nil
-}
-func (pow failPow) Hashrate() float64 { return 0 }
-
-// delayedPow is a non-validating proof of work implementation, that returns true
-// from Verify for all blocks, but delays them the configured amount of time.
-type delayedPow struct {
-	delay time.Duration
-}
-
-func (pow delayedPow) Search(pow.Block, <-chan struct{}) (uint64, []byte) {
-	return 0, nil
-}
-func (pow delayedPow) Verify(block pow.Block) error { time.Sleep(pow.delay); return nil }
-func (pow delayedPow) Hashrate() float64            { return 0 }
-
-// Tests that simple POW verification works, for both good and bad blocks.
-func TestPowVerification(t *testing.T) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Run the POW checker for blocks one-by-one, checking for both valid and invalid nonces
-	for i := 0; i < len(blocks); i++ {
-		for j, full := range []bool{true, false} {
-			for k, valid := range []bool{true, false} {
-				var results <-chan nonceCheckResult
-
-				switch {
-				case full && valid:
-					_, results = verifyNoncesFromBlocks(pow.FakePow{}, []*types.Block{blocks[i]})
-				case full && !valid:
-					_, results = verifyNoncesFromBlocks(failPow{blocks[i].NumberU64()}, []*types.Block{blocks[i]})
-				case !full && valid:
-					_, results = verifyNoncesFromHeaders(pow.FakePow{}, []*types.Header{headers[i]})
-				case !full && !valid:
-					_, results = verifyNoncesFromHeaders(failPow{headers[i].Number.Uint64()}, []*types.Header{headers[i]})
-				}
-				// Wait for the verification result
-				select {
-				case result := <-results:
-					if result.index != 0 {
-						t.Errorf("test %d.%d.%d: invalid index: have %d, want 0", i, j, k, result.index)
-					}
-					if result.valid != valid {
-						t.Errorf("test %d.%d.%d: validity mismatch: have %v, want %v", i, j, k, result.valid, valid)
-					}
-				case <-time.After(time.Second):
-					t.Fatalf("test %d.%d.%d: verification timeout", i, j, k)
-				}
-				// Make sure no more data is returned
-				select {
-				case result := <-results:
-					t.Fatalf("test %d.%d.%d: unexpected result returned: %v", i, j, k, result)
-				case <-time.After(25 * time.Millisecond):
-				}
-			}
-		}
-	}
-}
-
-// Tests that concurrent POW verification works, for both good and bad blocks.
-func TestPowConcurrentVerification2(t *testing.T)  { testPowConcurrentVerification(t, 2) }
-func TestPowConcurrentVerification8(t *testing.T)  { testPowConcurrentVerification(t, 8) }
-func TestPowConcurrentVerification32(t *testing.T) { testPowConcurrentVerification(t, 32) }
-
-func testPowConcurrentVerification(t *testing.T, threads int) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 8, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Set the number of threads to verify on
-	old := runtime.GOMAXPROCS(threads)
-	defer runtime.GOMAXPROCS(old)
-
-	// Run the POW checker for the entire block chain at once both for a valid and
-	// also an invalid chain (enough if one is invalid, last but one (arbitrary)).
-	for i, full := range []bool{true, false} {
-		for j, valid := range []bool{true, false} {
-			var results <-chan nonceCheckResult
-
-			switch {
-			case full && valid:
-				_, results = verifyNoncesFromBlocks(pow.FakePow{}, blocks)
-			case full && !valid:
-				_, results = verifyNoncesFromBlocks(failPow{uint64(len(blocks) - 1)}, blocks)
-			case !full && valid:
-				_, results = verifyNoncesFromHeaders(pow.FakePow{}, headers)
-			case !full && !valid:
-				_, results = verifyNoncesFromHeaders(failPow{uint64(len(headers) - 1)}, headers)
-			}
-			// Wait for all the verification results
-			checks := make(map[int]bool)
-			for k := 0; k < len(blocks); k++ {
-				select {
-				case result := <-results:
-					if _, ok := checks[result.index]; ok {
-						t.Fatalf("test %d.%d.%d: duplicate results for %d", i, j, k, result.index)
-					}
-					if result.index < 0 || result.index >= len(blocks) {
-						t.Fatalf("test %d.%d.%d: result %d out of bounds [%d, %d]", i, j, k, result.index, 0, len(blocks)-1)
-					}
-					checks[result.index] = result.valid
-
-				case <-time.After(time.Second):
-					t.Fatalf("test %d.%d.%d: verification timeout", i, j, k)
-				}
-			}
-			// Check nonce check validity
-			for k := 0; k < len(blocks); k++ {
-				want := valid || (k != len(blocks)-2) // We chose the last but one nonce in the chain to fail
-				if checks[k] != want {
-					t.Errorf("test %d.%d.%d: validity mismatch: have %v, want %v", i, j, k, checks[k], want)
-				}
-			}
-			// Make sure no more data is returned
-			select {
-			case result := <-results:
-				t.Fatalf("test %d.%d: unexpected result returned: %v", i, j, result)
-			case <-time.After(25 * time.Millisecond):
-			}
-		}
-	}
-}
-
-// Tests that aborting a POW validation indeed prevents further checks from being
-// run, as well as checks that no left-over goroutines are leaked.
-func TestPowConcurrentAbortion2(t *testing.T)  { testPowConcurrentAbortion(t, 2) }
-func TestPowConcurrentAbortion8(t *testing.T)  { testPowConcurrentAbortion(t, 8) }
-func TestPowConcurrentAbortion32(t *testing.T) { testPowConcurrentAbortion(t, 32) }
-
-func testPowConcurrentAbortion(t *testing.T, threads int) {
-	// Create a simple chain to verify
-	var (
-		testdb, _ = ethdb.NewMemDatabase()
-		genesis   = GenesisBlockForTesting(testdb, common.Address{}, new(big.Int))
-		blocks, _ = GenerateChain(params.TestChainConfig, genesis, testdb, 1024, nil)
-	)
-	headers := make([]*types.Header, len(blocks))
-	for i, block := range blocks {
-		headers[i] = block.Header()
-	}
-	// Set the number of threads to verify on
-	old := runtime.GOMAXPROCS(threads)
-	defer runtime.GOMAXPROCS(old)
-
-	// Run the POW checker for the entire block chain at once
-	for i, full := range []bool{true, false} {
-		var abort chan<- struct{}
-		var results <-chan nonceCheckResult
-
-		// Start the verifications and immediately abort
-		if full {
-			abort, results = verifyNoncesFromBlocks(delayedPow{time.Millisecond}, blocks)
-		} else {
-			abort, results = verifyNoncesFromHeaders(delayedPow{time.Millisecond}, headers)
-		}
-		close(abort)
-
-		// Deplete the results channel
-		verified := make(map[int]struct{})
-		for depleted := false; !depleted; {
-			select {
-			case result := <-results:
-				verified[result.index] = struct{}{}
-			case <-time.After(50 * time.Millisecond):
-				depleted = true
-			}
-		}
-		// Check that abortion was honored by not processing too many POWs
-		if len(verified) > 2*threads {
-			t.Errorf("test %d: verification count too large: have %d, want below %d", i, len(verified), 2*threads)
-		}
-		// Check that there are no gaps in the results
-		for j := 0; j < len(verified); j++ {
-			if _, ok := verified[j]; !ok {
-				t.Errorf("test %d.%d: gap found in verification results", i, j)
-			}
-		}
-	}
-}
diff --git a/core/dao_test.go b/core/dao_test.go
index c0d482630..cb6e54f8f 100644
--- a/core/dao_test.go
+++ b/core/dao_test.go
@@ -20,11 +20,11 @@ import (
 	"math/big"
 	"testing"
 
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // Tests that DAO-fork enabled clients can properly filter out fork-commencing
@@ -42,12 +42,12 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	proDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(proDb)
 	proConf := &params.ChainConfig{HomesteadBlock: big.NewInt(0), DAOForkBlock: forkBlock, DAOForkSupport: true}
-	proBc, _ := NewBlockChain(proDb, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	proBc, _ := NewBlockChain(proDb, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	conDb, _ := ethdb.NewMemDatabase()
 	gspec.MustCommit(conDb)
 	conConf := &params.ChainConfig{HomesteadBlock: big.NewInt(0), DAOForkBlock: forkBlock, DAOForkSupport: false}
-	conBc, _ := NewBlockChain(conDb, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	conBc, _ := NewBlockChain(conDb, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	if _, err := proBc.InsertChain(prefix); err != nil {
 		t.Fatalf("pro-fork: failed to import chain prefix: %v", err)
@@ -60,7 +60,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		// Create a pro-fork block, and try to feed into the no-fork chain
 		db, _ = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
-		bc, _ := NewBlockChain(db, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+		bc, _ := NewBlockChain(db, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 		blocks := conBc.GetBlocksFromHash(conBc.CurrentBlock().Hash(), int(conBc.CurrentBlock().NumberU64()+1))
 		for j := 0; j < len(blocks)/2; j++ {
@@ -81,7 +81,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		// Create a no-fork block, and try to feed into the pro-fork chain
 		db, _ = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
-		bc, _ = NewBlockChain(db, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+		bc, _ = NewBlockChain(db, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 		blocks = proBc.GetBlocksFromHash(proBc.CurrentBlock().Hash(), int(proBc.CurrentBlock().NumberU64()+1))
 		for j := 0; j < len(blocks)/2; j++ {
@@ -103,7 +103,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Verify that contra-forkers accept pro-fork extra-datas after forking finishes
 	db, _ = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
-	bc, _ := NewBlockChain(db, conConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	bc, _ := NewBlockChain(db, conConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	blocks := conBc.GetBlocksFromHash(conBc.CurrentBlock().Hash(), int(conBc.CurrentBlock().NumberU64()+1))
 	for j := 0; j < len(blocks)/2; j++ {
@@ -119,7 +119,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Verify that pro-forkers accept contra-fork extra-datas after forking finishes
 	db, _ = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
-	bc, _ = NewBlockChain(db, proConf, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	bc, _ = NewBlockChain(db, proConf, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 
 	blocks = proBc.GetBlocksFromHash(proBc.CurrentBlock().Hash(), int(proBc.CurrentBlock().NumberU64()+1))
 	for j := 0; j < len(blocks)/2; j++ {
diff --git a/core/database_util_test.go b/core/database_util_test.go
index e6be06093..9f16b660a 100644
--- a/core/database_util_test.go
+++ b/core/database_util_test.go
@@ -18,14 +18,12 @@ package core
 
 import (
 	"bytes"
-	"encoding/json"
 	"io/ioutil"
 	"math/big"
 	"os"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
@@ -34,58 +32,6 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-type diffTest struct {
-	ParentTimestamp    uint64
-	ParentDifficulty   *big.Int
-	CurrentTimestamp   uint64
-	CurrentBlocknumber *big.Int
-	CurrentDifficulty  *big.Int
-}
-
-func (d *diffTest) UnmarshalJSON(b []byte) (err error) {
-	var ext struct {
-		ParentTimestamp    string
-		ParentDifficulty   string
-		CurrentTimestamp   string
-		CurrentBlocknumber string
-		CurrentDifficulty  string
-	}
-	if err := json.Unmarshal(b, &ext); err != nil {
-		return err
-	}
-
-	d.ParentTimestamp = math.MustParseUint64(ext.ParentTimestamp)
-	d.ParentDifficulty = math.MustParseBig256(ext.ParentDifficulty)
-	d.CurrentTimestamp = math.MustParseUint64(ext.CurrentTimestamp)
-	d.CurrentBlocknumber = math.MustParseBig256(ext.CurrentBlocknumber)
-	d.CurrentDifficulty = math.MustParseBig256(ext.CurrentDifficulty)
-
-	return nil
-}
-
-func TestCalcDifficulty(t *testing.T) {
-	file, err := os.Open("../tests/files/BasicTests/difficulty.json")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer file.Close()
-
-	tests := make(map[string]diffTest)
-	err = json.NewDecoder(file).Decode(&tests)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
-	for name, test := range tests {
-		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
-		diff := CalcDifficulty(config, test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
-		if diff.Cmp(test.CurrentDifficulty) != 0 {
-			t.Error(name, "failed. Expected", test.CurrentDifficulty, "and calculated", diff)
-		}
-	}
-}
-
 // Tests block header storage and retrieval operations.
 func TestHeaderStorage(t *testing.T) {
 	db, _ := ethdb.NewMemDatabase()
@@ -562,7 +508,11 @@ func TestMipmapChain(t *testing.T) {
 	)
 	defer db.Close()
 
-	genesis := testGenesis(addr, big.NewInt(1000000)).MustCommit(db)
+	gspec := &Genesis{
+		Config: params.TestChainConfig,
+		Alloc:  GenesisAlloc{addr: {Balance: big.NewInt(1000000)}},
+	}
+	genesis := gspec.MustCommit(db)
 	chain, receipts := GenerateChain(params.TestChainConfig, genesis, db, 1010, func(i int, gen *BlockGen) {
 		var receipts types.Receipts
 		switch i {
diff --git a/core/genesis_test.go b/core/genesis_test.go
index b73dd776f..4312a80b8 100644
--- a/core/genesis_test.go
+++ b/core/genesis_test.go
@@ -23,11 +23,11 @@ import (
 
 	"github.com/davecgh/go-spew/spew"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 func TestDefaultGenesisBlock(t *testing.T) {
@@ -119,7 +119,7 @@ func TestSetupGenesis(t *testing.T) {
 				// Commit the 'old' genesis block with Homestead transition at #2.
 				// Advance to block #4, past the homestead transition block of customg.
 				genesis := oldcustomg.MustCommit(db)
-				bc, _ := NewBlockChain(db, oldcustomg.Config, pow.FakePow{}, new(event.TypeMux), vm.Config{})
+				bc, _ := NewBlockChain(db, oldcustomg.Config, ethash.NewFullFaker(), new(event.TypeMux), vm.Config{})
 				bc.SetValidator(bproc{})
 				bc.InsertChain(makeBlockChainWithDiff(genesis, []int{2, 3, 4, 5}, 0))
 				bc.CurrentBlock()
diff --git a/core/headerchain.go b/core/headerchain.go
index e7660cc60..e2d0ff5b1 100644
--- a/core/headerchain.go
+++ b/core/headerchain.go
@@ -18,21 +18,19 @@ package core
 
 import (
 	crand "crypto/rand"
+	"errors"
 	"fmt"
 	"math"
 	"math/big"
 	mrand "math/rand"
-	"runtime"
-	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/hashicorp/golang-lru"
 )
 
@@ -62,18 +60,15 @@ type HeaderChain struct {
 
 	procInterrupt func() bool
 
-	rand         *mrand.Rand
-	getValidator getHeaderValidatorFn
+	rand   *mrand.Rand
+	engine consensus.Engine
 }
 
-// getHeaderValidatorFn returns a HeaderValidator interface
-type getHeaderValidatorFn func() HeaderValidator
-
 // NewHeaderChain creates a new HeaderChain structure.
 //  getValidator should return the parent's validator
 //  procInterrupt points to the parent's interrupt semaphore
 //  wg points to the parent's shutdown wait group
-func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, getValidator getHeaderValidatorFn, procInterrupt func() bool) (*HeaderChain, error) {
+func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, engine consensus.Engine, procInterrupt func() bool) (*HeaderChain, error) {
 	headerCache, _ := lru.New(headerCacheLimit)
 	tdCache, _ := lru.New(tdCacheLimit)
 	numberCache, _ := lru.New(numberCacheLimit)
@@ -92,7 +87,7 @@ func NewHeaderChain(chainDb ethdb.Database, config *params.ChainConfig, getValid
 		numberCache:   numberCache,
 		procInterrupt: procInterrupt,
 		rand:          mrand.New(mrand.NewSource(seed.Int64())),
-		getValidator:  getValidator,
+		engine:        engine,
 	}
 
 	hc.genesisHeader = hc.GetHeaderByNumber(0)
@@ -228,78 +223,34 @@ func (hc *HeaderChain) ValidateHeaderChain(chain []*types.Header, checkFreq int)
 		}
 	}
 
-	// Generate the list of headers that should be POW verified
-	verify := make([]bool, len(chain))
-	for i := 0; i < len(verify)/checkFreq; i++ {
+	// Generate the list of seal verification requests, and start the parallel verifier
+	seals := make([]bool, len(chain))
+	for i := 0; i < len(seals)/checkFreq; i++ {
 		index := i*checkFreq + hc.rand.Intn(checkFreq)
-		if index >= len(verify) {
-			index = len(verify) - 1
+		if index >= len(seals) {
+			index = len(seals) - 1
 		}
-		verify[index] = true
-	}
-	verify[len(verify)-1] = true // Last should always be verified to avoid junk
-
-	// Create the header verification task queue and worker functions
-	tasks := make(chan int, len(chain))
-	for i := 0; i < len(chain); i++ {
-		tasks <- i
+		seals[index] = true
 	}
-	close(tasks)
+	seals[len(seals)-1] = true // Last should always be verified to avoid junk
 
-	errs, failed := make([]error, len(tasks)), int32(0)
-	process := func(worker int) {
-		for index := range tasks {
-			header, hash := chain[index], chain[index].Hash()
+	abort, results := hc.engine.VerifyHeaders(hc, chain, seals)
+	defer close(abort)
 
-			// Short circuit insertion if shutting down or processing failed
-			if hc.procInterrupt() {
-				return
-			}
-			if atomic.LoadInt32(&failed) > 0 {
-				return
-			}
-			// Short circuit if the header is bad or already known
-			if BadHashes[hash] {
-				errs[index] = BadHashError(hash)
-				atomic.AddInt32(&failed, 1)
-				return
-			}
-			if hc.HasHeader(hash) {
-				continue
-			}
-			// Verify that the header honors the chain parameters
-			checkPow := verify[index]
-
-			var err error
-			if index == 0 {
-				err = hc.getValidator().ValidateHeader(header, hc.GetHeader(header.ParentHash, header.Number.Uint64()-1), checkPow)
-			} else {
-				err = hc.getValidator().ValidateHeader(header, chain[index-1], checkPow)
-			}
-			if err != nil {
-				errs[index] = err
-				atomic.AddInt32(&failed, 1)
-				return
-			}
+	// Iterate over the headers and ensure they all check out
+	for i, header := range chain {
+		// If the chain is terminating, stop processing blocks
+		if hc.procInterrupt() {
+			log.Debug("Premature abort during headers verification")
+			return 0, errors.New("aborted")
 		}
-	}
-	// Start as many worker threads as goroutines allowed
-	pending := new(sync.WaitGroup)
-	for i := 0; i < runtime.GOMAXPROCS(0); i++ {
-		pending.Add(1)
-		go func(id int) {
-			defer pending.Done()
-			process(id)
-		}(i)
-	}
-	pending.Wait()
-
-	// If anything failed, report
-	if failed > 0 {
-		for i, err := range errs {
-			if err != nil {
-				return i, err
-			}
+		// If the header is a banned one, straight out abort
+		if BadHashes[header.Hash()] {
+			return i, BadHashError(header.Hash())
+		}
+		// Otherwise wait for headers checks and ensure they pass
+		if err := <-results; err != nil {
+			return i, err
 		}
 	}
 
@@ -313,13 +264,11 @@ func (hc *HeaderChain) InsertHeaderChain(chain []*types.Header, writeHeader WhCa
 	for i, header := range chain {
 		// Short circuit insertion if shutting down
 		if hc.procInterrupt() {
-			log.Debug("Premature abort during headers processing")
-			break
+			log.Debug("Premature abort during headers import")
+			return i, errors.New("aborted")
 		}
-		hash := header.Hash()
-
 		// If the header's already known, skip it, otherwise store
-		if hc.HasHeader(hash) {
+		if hc.GetHeader(header.Hash(), header.Number.Uint64()) != nil {
 			stats.ignored++
 			continue
 		}
@@ -490,35 +439,11 @@ func (hc *HeaderChain) SetGenesis(head *types.Header) {
 	hc.genesisHeader = head
 }
 
-// headerValidator is responsible for validating block headers
-//
-// headerValidator implements HeaderValidator.
-type headerValidator struct {
-	config *params.ChainConfig
-	hc     *HeaderChain // Canonical header chain
-	Pow    pow.PoW      // Proof of work used for validating
-}
-
-// NewBlockValidator returns a new block validator which is safe for re-use
-func NewHeaderValidator(config *params.ChainConfig, chain *HeaderChain, pow pow.PoW) HeaderValidator {
-	return &headerValidator{
-		config: config,
-		Pow:    pow,
-		hc:     chain,
-	}
-}
+// Config retrieves the header chain's chain configuration.
+func (hc *HeaderChain) Config() *params.ChainConfig { return hc.config }
 
-// ValidateHeader validates the given header and, depending on the pow arg,
-// checks the proof of work of the given header. Returns an error if the
-// validation failed.
-func (v *headerValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
-	// Short circuit if the parent is missing.
-	if parent == nil {
-		return ParentError(header.ParentHash)
-	}
-	// Short circuit if the header's already known or its parent missing
-	if v.hc.HasHeader(header.Hash()) {
-		return nil
-	}
-	return ValidateHeader(v.config, v.Pow, header, parent, checkPow, false)
+// GetBlock implements consensus.ChainReader, and returns nil for every input as
+// a header chain does not have blocks available for retrieval.
+func (hc *HeaderChain) GetBlock(hash common.Hash, number uint64) *types.Block {
+	return nil
 }
diff --git a/core/state_processor.go b/core/state_processor.go
index 3edc042a3..aca2929eb 100644
--- a/core/state_processor.go
+++ b/core/state_processor.go
@@ -19,6 +19,8 @@ package core
 import (
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -26,25 +28,22 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
-var (
-	big8  = big.NewInt(8)
-	big32 = big.NewInt(32)
-)
-
 // StateProcessor is a basic Processor, which takes care of transitioning
 // state from one point to another.
 //
 // StateProcessor implements Processor.
 type StateProcessor struct {
-	config *params.ChainConfig
-	bc     *BlockChain
+	config *params.ChainConfig // Chain configuration options
+	bc     *BlockChain         // Canonical block chain
+	engine consensus.Engine    // Consensus engine used for block rewards
 }
 
 // NewStateProcessor initialises a new StateProcessor.
-func NewStateProcessor(config *params.ChainConfig, bc *BlockChain) *StateProcessor {
+func NewStateProcessor(config *params.ChainConfig, bc *BlockChain, engine consensus.Engine) *StateProcessor {
 	return &StateProcessor{
 		config: config,
 		bc:     bc,
+		engine: engine,
 	}
 }
 
@@ -59,18 +58,16 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 	var (
 		receipts     types.Receipts
 		totalUsedGas = big.NewInt(0)
-		err          error
 		header       = block.Header()
 		allLogs      []*types.Log
 		gp           = new(GasPool).AddGas(block.GasLimit())
 	)
 	// Mutate the the block and state according to any hard-fork specs
 	if p.config.DAOForkSupport && p.config.DAOForkBlock != nil && p.config.DAOForkBlock.Cmp(block.Number()) == 0 {
-		ApplyDAOHardFork(statedb)
+		misc.ApplyDAOHardFork(statedb)
 	}
 	// Iterate over and process the individual transactions
 	for i, tx := range block.Transactions() {
-		//fmt.Println("tx:", i)
 		statedb.StartRecord(tx.Hash(), block.Hash(), i)
 		receipt, _, err := ApplyTransaction(p.config, p.bc, gp, statedb, header, tx, totalUsedGas, cfg)
 		if err != nil {
@@ -79,9 +76,10 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 		receipts = append(receipts, receipt)
 		allLogs = append(allLogs, receipt.Logs...)
 	}
-	AccumulateRewards(statedb, header, block.Uncles())
+	// Finalize the block, applying any consensus engine specific extras (e.g. block rewards)
+	p.engine.Finalize(p.bc, header, statedb, block.Transactions(), block.Uncles(), receipts)
 
-	return receipts, allLogs, totalUsedGas, err
+	return receipts, allLogs, totalUsedGas, nil
 }
 
 // ApplyTransaction attempts to apply a transaction to the given state database
@@ -122,23 +120,3 @@ func ApplyTransaction(config *params.ChainConfig, bc *BlockChain, gp *GasPool, s
 
 	return receipt, gas, err
 }
-
-// AccumulateRewards credits the coinbase of the given block with the
-// mining reward. The total reward consists of the static block reward
-// and rewards for included uncles. The coinbase of each uncle block is
-// also rewarded.
-func AccumulateRewards(statedb *state.StateDB, header *types.Header, uncles []*types.Header) {
-	reward := new(big.Int).Set(BlockReward)
-	r := new(big.Int)
-	for _, uncle := range uncles {
-		r.Add(uncle.Number, big8)
-		r.Sub(r, header.Number)
-		r.Mul(r, BlockReward)
-		r.Div(r, big8)
-		statedb.AddBalance(uncle.Coinbase, r)
-
-		r.Div(BlockReward, big32)
-		reward.Add(reward, r)
-	}
-	statedb.AddBalance(header.Coinbase, reward)
-}
diff --git a/core/types.go b/core/types.go
index 7fd658979..1cfbbab29 100644
--- a/core/types.go
+++ b/core/types.go
@@ -24,31 +24,17 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
-// Validator is an interface which defines the standard for block validation.
+// Validator is an interface which defines the standard for block validation. It
+// is only responsible for validating block contents, as the header validation is
+// done by the specific consensus engines.
 //
-// The validator is responsible for validating incoming block or, if desired,
-// validates headers for fast validation.
-//
-// ValidateBlock validates the given block and should return an error if it
-// failed to do so and should be used for "full" validation.
-//
-// ValidateHeader validates the given header and parent and returns an error
-// if it failed to do so.
-//
-// ValidateState validates the given statedb and optionally the receipts and
-// gas used. The implementer should decide what to do with the given input.
 type Validator interface {
-	HeaderValidator
-	ValidateBlock(block *types.Block) error
-	ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error
-}
+	// ValidateBody validates the given block's content.
+	ValidateBody(block *types.Block) error
 
-// HeaderValidator is an interface for validating headers only
-//
-// ValidateHeader validates the given header and parent and returns an error
-// if it failed to do so.
-type HeaderValidator interface {
-	ValidateHeader(header, parent *types.Header, checkPow bool) error
+	// ValidateState validates the given statedb and optionally the receipts and
+	// gas used.
+	ValidateState(block, parent *types.Block, state *state.StateDB, receipts types.Receipts, usedGas *big.Int) error
 }
 
 // Processor is an interface for processing blocks using a given initial state.
diff --git a/core/types/block.go b/core/types/block.go
index b699ba686..278594d50 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -348,12 +348,11 @@ func CalcUncleHash(uncles []*Header) common.Hash {
 	return rlpHash(uncles)
 }
 
-// WithMiningResult returns a new block with the data from b
-// where nonce and mix digest are set to the provided values.
-func (b *Block) WithMiningResult(nonce BlockNonce, mixDigest common.Hash) *Block {
-	cpy := *b.header
-	cpy.Nonce = nonce
-	cpy.MixDigest = mixDigest
+// WithSeal returns a new block with the data from b but the header replaced with
+// the sealed one.
+func (b *Block) WithSeal(header *Header) *Block {
+	cpy := *header
+
 	return &Block{
 		header:       &cpy,
 		transactions: b.transactions,
diff --git a/eth/api.go b/eth/api.go
index b64153fd7..58ae27df2 100644
--- a/eth/api.go
+++ b/eth/api.go
@@ -26,7 +26,6 @@ import (
 	"io/ioutil"
 	"math/big"
 	"os"
-	"runtime"
 	"strings"
 	"time"
 
@@ -37,6 +36,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/miner"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -56,18 +56,18 @@ func NewPublicEthereumAPI(e *Ethereum) *PublicEthereumAPI {
 }
 
 // Etherbase is the address that mining rewards will be send to
-func (s *PublicEthereumAPI) Etherbase() (common.Address, error) {
-	return s.e.Etherbase()
+func (api *PublicEthereumAPI) Etherbase() (common.Address, error) {
+	return api.e.Etherbase()
 }
 
 // Coinbase is the address that mining rewards will be send to (alias for Etherbase)
-func (s *PublicEthereumAPI) Coinbase() (common.Address, error) {
-	return s.Etherbase()
+func (api *PublicEthereumAPI) Coinbase() (common.Address, error) {
+	return api.Etherbase()
 }
 
 // Hashrate returns the POW hashrate
-func (s *PublicEthereumAPI) Hashrate() hexutil.Uint64 {
-	return hexutil.Uint64(s.e.Miner().HashRate())
+func (api *PublicEthereumAPI) Hashrate() hexutil.Uint64 {
+	return hexutil.Uint64(api.e.Miner().HashRate())
 }
 
 // PublicMinerAPI provides an API to control the miner.
@@ -79,34 +79,34 @@ type PublicMinerAPI struct {
 
 // NewPublicMinerAPI create a new PublicMinerAPI instance.
 func NewPublicMinerAPI(e *Ethereum) *PublicMinerAPI {
-	agent := miner.NewRemoteAgent(e.Pow())
+	agent := miner.NewRemoteAgent(e.BlockChain(), e.Engine())
 	e.Miner().Register(agent)
 
 	return &PublicMinerAPI{e, agent}
 }
 
 // Mining returns an indication if this node is currently mining.
-func (s *PublicMinerAPI) Mining() bool {
-	return s.e.IsMining()
+func (api *PublicMinerAPI) Mining() bool {
+	return api.e.IsMining()
 }
 
 // SubmitWork can be used by external miner to submit their POW solution. It returns an indication if the work was
 // accepted. Note, this is not an indication if the provided work was valid!
-func (s *PublicMinerAPI) SubmitWork(nonce types.BlockNonce, solution, digest common.Hash) bool {
-	return s.agent.SubmitWork(nonce, digest, solution)
+func (api *PublicMinerAPI) SubmitWork(nonce types.BlockNonce, solution, digest common.Hash) bool {
+	return api.agent.SubmitWork(nonce, digest, solution)
 }
 
 // GetWork returns a work package for external miner. The work package consists of 3 strings
 // result[0], 32 bytes hex encoded current block header pow-hash
 // result[1], 32 bytes hex encoded seed hash used for DAG
 // result[2], 32 bytes hex encoded boundary condition ("target"), 2^256/difficulty
-func (s *PublicMinerAPI) GetWork() ([3]string, error) {
-	if !s.e.IsMining() {
-		if err := s.e.StartMining(0); err != nil {
+func (api *PublicMinerAPI) GetWork() ([3]string, error) {
+	if !api.e.IsMining() {
+		if err := api.e.StartMining(); err != nil {
 			return [3]string{}, err
 		}
 	}
-	work, err := s.agent.GetWork()
+	work, err := api.agent.GetWork()
 	if err != nil {
 		return work, fmt.Errorf("mining not ready: %v", err)
 	}
@@ -116,8 +116,8 @@ func (s *PublicMinerAPI) GetWork() ([3]string, error) {
 // SubmitHashrate can be used for remote miners to submit their hash rate. This enables the node to report the combined
 // hash rate of all miners which submit work through this node. It accepts the miner hash rate and an identifier which
 // must be unique between nodes.
-func (s *PublicMinerAPI) SubmitHashrate(hashrate hexutil.Uint64, id common.Hash) bool {
-	s.agent.SubmitHashrate(id, uint64(hashrate))
+func (api *PublicMinerAPI) SubmitHashrate(hashrate hexutil.Uint64, id common.Hash) bool {
+	api.agent.SubmitHashrate(id, uint64(hashrate))
 	return true
 }
 
@@ -132,47 +132,59 @@ func NewPrivateMinerAPI(e *Ethereum) *PrivateMinerAPI {
 	return &PrivateMinerAPI{e: e}
 }
 
-// Start the miner with the given number of threads. If threads is nil the number of
-// workers started is equal to the number of logical CPU's that are usable by this process.
-func (s *PrivateMinerAPI) Start(threads *int) (bool, error) {
-	var err error
-	if threads == nil {
-		err = s.e.StartMining(runtime.NumCPU())
-	} else {
-		err = s.e.StartMining(*threads)
+// Start the miner with the given number of threads. If threads is nil the number
+// of workers started is equal to the number of logical CPUs that are usable by
+// this process. If mining is already running, this method adjust the number of
+// threads allowed to use.
+func (api *PrivateMinerAPI) Start(threads *int) error {
+	// Set the number of threads if the seal engine supports it
+	if threads != nil {
+		type threaded interface {
+			SetThreads(threads int)
+		}
+		if th, ok := api.e.engine.(threaded); ok {
+			log.Info("Updated mining threads", "threads", *threads)
+			th.SetThreads(*threads)
+		} else {
+			log.Warn("Current seal engine isn't threaded")
+		}
 	}
-	return err == nil, err
+	// Start the miner and return
+	if !api.e.IsMining() {
+		return api.e.StartMining()
+	}
+	return nil
 }
 
 // Stop the miner
-func (s *PrivateMinerAPI) Stop() bool {
-	s.e.StopMining()
+func (api *PrivateMinerAPI) Stop() bool {
+	api.e.StopMining()
 	return true
 }
 
 // SetExtra sets the extra data string that is included when this miner mines a block.
-func (s *PrivateMinerAPI) SetExtra(extra string) (bool, error) {
-	if err := s.e.Miner().SetExtra([]byte(extra)); err != nil {
+func (api *PrivateMinerAPI) SetExtra(extra string) (bool, error) {
+	if err := api.e.Miner().SetExtra([]byte(extra)); err != nil {
 		return false, err
 	}
 	return true, nil
 }
 
 // SetGasPrice sets the minimum accepted gas price for the miner.
-func (s *PrivateMinerAPI) SetGasPrice(gasPrice hexutil.Big) bool {
-	s.e.Miner().SetGasPrice((*big.Int)(&gasPrice))
+func (api *PrivateMinerAPI) SetGasPrice(gasPrice hexutil.Big) bool {
+	api.e.Miner().SetGasPrice((*big.Int)(&gasPrice))
 	return true
 }
 
 // SetEtherbase sets the etherbase of the miner
-func (s *PrivateMinerAPI) SetEtherbase(etherbase common.Address) bool {
-	s.e.SetEtherbase(etherbase)
+func (api *PrivateMinerAPI) SetEtherbase(etherbase common.Address) bool {
+	api.e.SetEtherbase(etherbase)
 	return true
 }
 
 // GetHashrate returns the current hashrate of the miner.
-func (s *PrivateMinerAPI) GetHashrate() uint64 {
-	return uint64(s.e.miner.HashRate())
+func (api *PrivateMinerAPI) GetHashrate() uint64 {
+	return uint64(api.e.miner.HashRate())
 }
 
 // PrivateAdminAPI is the collection of Etheruem full node-related APIs
@@ -321,7 +333,7 @@ type TraceArgs struct {
 	Timeout *string
 }
 
-// TraceBlock processes the given block's RLP but does not import the block in to
+// TraceBlock processes the given block'api RLP but does not import the block in to
 // the chain.
 func (api *PrivateDebugAPI) TraceBlock(blockRlp []byte, config *vm.LogConfig) BlockTraceResult {
 	var block types.Block
@@ -338,7 +350,7 @@ func (api *PrivateDebugAPI) TraceBlock(blockRlp []byte, config *vm.LogConfig) Bl
 	}
 }
 
-// TraceBlockFromFile loads the block's RLP from the given file name and attempts to
+// TraceBlockFromFile loads the block'api RLP from the given file name and attempts to
 // process it but does not import the block in to the chain.
 func (api *PrivateDebugAPI) TraceBlockFromFile(file string, config *vm.LogConfig) BlockTraceResult {
 	blockRlp, err := ioutil.ReadFile(file)
@@ -395,8 +407,7 @@ func (api *PrivateDebugAPI) traceBlock(block *types.Block, logConfig *vm.LogConf
 		Debug:  true,
 		Tracer: structLogger,
 	}
-
-	if err := core.ValidateHeader(api.config, blockchain.AuxValidator(), block.Header(), blockchain.GetHeader(block.ParentHash(), block.NumberU64()-1), true, false); err != nil {
+	if err := api.eth.engine.VerifyHeader(blockchain, block.Header(), true); err != nil {
 		return false, structLogger.StructLogs(), err
 	}
 	statedb, err := blockchain.StateAt(blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1).Root())
diff --git a/eth/backend.go b/eth/backend.go
index b8df98976..af1d46a2c 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -22,10 +22,11 @@ import (
 	"math/big"
 	"regexp"
 	"sync"
-	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -40,18 +41,9 @@ import (
 	"github.com/ethereum/go-ethereum/node"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rpc"
 )
 
-const (
-	epochLength    = 30000
-	ethashRevision = 23
-
-	autoDAGcheckInterval = 10 * time.Hour
-	autoDAGepochHeight   = epochLength / 2
-)
-
 var (
 	datadirInUseErrnos = map[uint]bool{11: true, 32: true, 35: true}
 	portInUseErrRE     = regexp.MustCompile("address already in use")
@@ -124,7 +116,7 @@ type Ethereum struct {
 	chainDb ethdb.Database // Block chain database
 
 	eventMux       *event.TypeMux
-	pow            pow.PoW
+	engine         consensus.Engine
 	accountManager *accounts.Manager
 
 	ApiBackend *EthApiBackend
@@ -163,7 +155,7 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 		chainConfig:    chainConfig,
 		eventMux:       ctx.EventMux,
 		accountManager: ctx.AccountManager,
-		pow:            CreatePoW(ctx, config),
+		engine:         CreateConsensusEngine(ctx, config, chainConfig, chainDb),
 		shutdownChan:   make(chan bool),
 		stopDbUpgrade:  stopDbUpgrade,
 		netVersionId:   config.NetworkId,
@@ -186,7 +178,7 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 	}
 
 	vmConfig := vm.Config{EnablePreimageRecording: config.EnablePreimageRecording}
-	eth.blockchain, err = core.NewBlockChain(chainDb, eth.chainConfig, eth.pow, eth.eventMux, vmConfig)
+	eth.blockchain, err = core.NewBlockChain(chainDb, eth.chainConfig, eth.engine, eth.eventMux, vmConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -211,10 +203,11 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 		}
 	}
 
-	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.FastSync, config.NetworkId, maxPeers, eth.eventMux, eth.txPool, eth.pow, eth.blockchain, chainDb); err != nil {
+	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.FastSync, config.NetworkId, maxPeers, eth.eventMux, eth.txPool, eth.engine, eth.blockchain, chainDb); err != nil {
 		return nil, err
 	}
-	eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.pow)
+
+	eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine)
 	eth.miner.SetGasPrice(config.GasPrice)
 	eth.miner.SetExtra(config.ExtraData)
 
@@ -241,20 +234,20 @@ func CreateDB(ctx *node.ServiceContext, config *Config, name string) (ethdb.Data
 	return db, err
 }
 
-// CreatePoW creates the required type of PoW instance for an Ethereum service
-func CreatePoW(ctx *node.ServiceContext, config *Config) pow.PoW {
+// CreateConsensusEngine creates the required type of consensus engine instance for an Ethereum service
+func CreateConsensusEngine(ctx *node.ServiceContext, config *Config, chainConfig *params.ChainConfig, db ethdb.Database) consensus.Engine {
 	switch {
 	case config.PowFake:
 		log.Warn("Ethash used in fake mode")
-		return pow.FakePow{}
+		return ethash.NewFaker()
 	case config.PowTest:
 		log.Warn("Ethash used in test mode")
-		return pow.NewTestEthash()
+		return ethash.NewTester()
 	case config.PowShared:
 		log.Warn("Ethash used in shared mode")
-		return pow.NewSharedEthash()
+		return ethash.NewShared()
 	default:
-		return pow.NewFullEthash(ctx.ResolvePath(config.EthashCacheDir), config.EthashCachesInMem, config.EthashCachesOnDisk,
+		return ethash.New(ctx.ResolvePath(config.EthashCacheDir), config.EthashCachesInMem, config.EthashCachesOnDisk,
 			config.EthashDatasetDir, config.EthashDatasetsInMem, config.EthashDatasetsOnDisk)
 	}
 }
@@ -262,7 +255,13 @@ func CreatePoW(ctx *node.ServiceContext, config *Config) pow.PoW {
 // APIs returns the collection of RPC services the ethereum package offers.
 // NOTE, some of these services probably need to be moved to somewhere else.
 func (s *Ethereum) APIs() []rpc.API {
-	return append(ethapi.GetAPIs(s.ApiBackend, s.solcPath), []rpc.API{
+	apis := ethapi.GetAPIs(s.ApiBackend, s.solcPath)
+
+	// Append any APIs exposed explicitly by the consensus engine
+	apis = append(apis, s.engine.APIs(s.BlockChain())...)
+
+	// Append all the local APIs and return
+	return append(apis, []rpc.API{
 		{
 			Namespace: "eth",
 			Version:   "1.0",
@@ -332,13 +331,13 @@ func (self *Ethereum) SetEtherbase(etherbase common.Address) {
 	self.miner.SetEtherbase(etherbase)
 }
 
-func (s *Ethereum) StartMining(threads int) error {
+func (s *Ethereum) StartMining() error {
 	eb, err := s.Etherbase()
 	if err != nil {
 		log.Error("Cannot start mining without etherbase", "err", err)
 		return fmt.Errorf("etherbase missing: %v", err)
 	}
-	go s.miner.Start(eb, threads)
+	go s.miner.Start(eb)
 	return nil
 }
 
@@ -350,7 +349,7 @@ func (s *Ethereum) AccountManager() *accounts.Manager  { return s.accountManager
 func (s *Ethereum) BlockChain() *core.BlockChain       { return s.blockchain }
 func (s *Ethereum) TxPool() *core.TxPool               { return s.txPool }
 func (s *Ethereum) EventMux() *event.TypeMux           { return s.eventMux }
-func (s *Ethereum) Pow() pow.PoW                       { return s.pow }
+func (s *Ethereum) Engine() consensus.Engine           { return s.engine }
 func (s *Ethereum) ChainDb() ethdb.Database            { return s.chainDb }
 func (s *Ethereum) IsListening() bool                  { return true } // Always listening
 func (s *Ethereum) EthVersion() int                    { return int(s.protocolManager.SubProtocols[0].Version) }
diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go
index d82f4f3e6..64a991069 100644
--- a/eth/fetcher/fetcher.go
+++ b/eth/fetcher/fetcher.go
@@ -52,8 +52,8 @@ type headerRequesterFn func(common.Hash) error
 // bodyRequesterFn is a callback type for sending a body retrieval request.
 type bodyRequesterFn func([]common.Hash) error
 
-// blockValidatorFn is a callback type to verify a block's header for fast propagation.
-type blockValidatorFn func(block *types.Block, parent *types.Block) error
+// headerVerifierFn is a callback type to verify a block's header for fast propagation.
+type headerVerifierFn func(header *types.Header) error
 
 // blockBroadcasterFn is a callback type for broadcasting a block to connected peers.
 type blockBroadcasterFn func(block *types.Block, propagate bool)
@@ -129,7 +129,7 @@ type Fetcher struct {
 
 	// Callbacks
 	getBlock       blockRetrievalFn   // Retrieves a block from the local chain
-	validateBlock  blockValidatorFn   // Checks if a block's headers have a valid proof of work
+	verifyHeader   headerVerifierFn   // Checks if a block's headers have a valid proof of work
 	broadcastBlock blockBroadcasterFn // Broadcasts a block to connected peers
 	chainHeight    chainHeightFn      // Retrieves the current chain's height
 	insertChain    chainInsertFn      // Injects a batch of blocks into the chain
@@ -144,7 +144,7 @@ type Fetcher struct {
 }
 
 // New creates a block fetcher to retrieve blocks based on hash announcements.
-func New(getBlock blockRetrievalFn, validateBlock blockValidatorFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher {
+func New(getBlock blockRetrievalFn, verifyHeader headerVerifierFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher {
 	return &Fetcher{
 		notify:         make(chan *announce),
 		inject:         make(chan *inject),
@@ -162,7 +162,7 @@ func New(getBlock blockRetrievalFn, validateBlock blockValidatorFn, broadcastBlo
 		queues:         make(map[string]int),
 		queued:         make(map[common.Hash]*inject),
 		getBlock:       getBlock,
-		validateBlock:  validateBlock,
+		verifyHeader:   verifyHeader,
 		broadcastBlock: broadcastBlock,
 		chainHeight:    chainHeight,
 		insertChain:    insertChain,
@@ -648,7 +648,7 @@ func (f *Fetcher) insert(peer string, block *types.Block) {
 			return
 		}
 		// Quickly validate the header and propagate the block if it passes
-		switch err := f.validateBlock(block, parent); err {
+		switch err := f.verifyHeader(block.Header()); err {
 		case nil:
 			// All ok, quickly propagate to our peers
 			propBroadcastOutTimer.UpdateSince(block.ReceivedAt)
diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
index 7a94241c6..85d2f8645 100644
--- a/eth/fetcher/fetcher_test.go
+++ b/eth/fetcher/fetcher_test.go
@@ -91,7 +91,7 @@ func newTester() *fetcherTester {
 		blocks: map[common.Hash]*types.Block{genesis.Hash(): genesis},
 		drops:  make(map[string]bool),
 	}
-	tester.fetcher = New(tester.getBlock, tester.verifyBlock, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
+	tester.fetcher = New(tester.getBlock, tester.verifyHeader, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
 	tester.fetcher.Start()
 
 	return tester
@@ -105,8 +105,8 @@ func (f *fetcherTester) getBlock(hash common.Hash) *types.Block {
 	return f.blocks[hash]
 }
 
-// verifyBlock is a nop placeholder for the block header verification.
-func (f *fetcherTester) verifyBlock(block *types.Block, parent *types.Block) error {
+// verifyHeader is a nop placeholder for the block header verification.
+func (f *fetcherTester) verifyHeader(header *types.Header) error {
 	return nil
 }
 
diff --git a/eth/handler.go b/eth/handler.go
index ade8f7719..445272060 100644
--- a/eth/handler.go
+++ b/eth/handler.go
@@ -27,6 +27,8 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/downloader"
@@ -37,7 +39,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
@@ -97,7 +98,7 @@ type ProtocolManager struct {
 
 // NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
 // with the ethereum network.
-func NewProtocolManager(config *params.ChainConfig, fastSync bool, networkId int, maxPeers int, mux *event.TypeMux, txpool txPool, pow pow.PoW, blockchain *core.BlockChain, chaindb ethdb.Database) (*ProtocolManager, error) {
+func NewProtocolManager(config *params.ChainConfig, fastSync bool, networkId int, maxPeers int, mux *event.TypeMux, txpool txPool, engine consensus.Engine, blockchain *core.BlockChain, chaindb ethdb.Database) (*ProtocolManager, error) {
 	// Create the protocol manager with the base fields
 	manager := &ProtocolManager{
 		networkId:   networkId,
@@ -165,8 +166,8 @@ func NewProtocolManager(config *params.ChainConfig, fastSync bool, networkId int
 		blockchain.GetTdByHash, blockchain.InsertHeaderChain, manager.insertChain, blockchain.InsertReceiptChain, blockchain.Rollback,
 		manager.removePeer)
 
-	validator := func(block *types.Block, parent *types.Block) error {
-		return core.ValidateHeader(config, pow, block.Header(), parent.Header(), true, false)
+	validator := func(header *types.Header) error {
+		return engine.VerifyHeader(blockchain, header, true)
 	}
 	heighter := func() uint64 {
 		return blockchain.CurrentBlock().NumberU64()
@@ -448,7 +449,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 				p.forkDrop = nil
 
 				// Validate the header and either drop the peer or continue
-				if err := core.ValidateDAOHeaderExtraData(pm.chainconfig, headers[0]); err != nil {
+				if err := misc.VerifyDAOHeaderExtraData(pm.chainconfig, headers[0]); err != nil {
 					p.Log().Debug("Verified to be on the other side of the DAO fork, dropping")
 					return err
 				}
diff --git a/eth/handler_test.go b/eth/handler_test.go
index 31435b331..f85d730b6 100644
--- a/eth/handler_test.go
+++ b/eth/handler_test.go
@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -34,7 +35,6 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 var bigTxGas = new(big.Int).SetUint64(params.TxGas)
@@ -469,7 +469,7 @@ func testDAOChallenge(t *testing.T, localForked, remoteForked bool, timeout bool
 	// Create a DAO aware protocol manager
 	var (
 		evmux         = new(event.TypeMux)
-		pow           = new(pow.FakePow)
+		pow           = ethash.NewFaker()
 		db, _         = ethdb.NewMemDatabase()
 		config        = &params.ChainConfig{DAOForkBlock: big.NewInt(1), DAOForkSupport: localForked}
 		gspec         = &core.Genesis{Config: config}
diff --git a/eth/helper_test.go b/eth/helper_test.go
index e67b49691..a8c538e6c 100644
--- a/eth/helper_test.go
+++ b/eth/helper_test.go
@@ -28,6 +28,7 @@ import (
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -37,7 +38,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 var (
@@ -50,22 +50,22 @@ var (
 // channels for different events.
 func newTestProtocolManager(fastSync bool, blocks int, generator func(int, *core.BlockGen), newtx chan<- []*types.Transaction) (*ProtocolManager, error) {
 	var (
-		evmux = new(event.TypeMux)
-		pow   = new(pow.FakePow)
-		db, _ = ethdb.NewMemDatabase()
-		gspec = &core.Genesis{
+		evmux  = new(event.TypeMux)
+		engine = ethash.NewFaker()
+		db, _  = ethdb.NewMemDatabase()
+		gspec  = &core.Genesis{
 			Config: params.TestChainConfig,
 			Alloc:  core.GenesisAlloc{testBank: {Balance: big.NewInt(1000000)}},
 		}
 		genesis       = gspec.MustCommit(db)
-		blockchain, _ = core.NewBlockChain(db, gspec.Config, pow, evmux, vm.Config{})
+		blockchain, _ = core.NewBlockChain(db, gspec.Config, engine, evmux, vm.Config{})
 	)
 	chain, _ := core.GenerateChain(gspec.Config, genesis, db, blocks, generator)
 	if _, err := blockchain.InsertChain(chain); err != nil {
 		panic(err)
 	}
 
-	pm, err := NewProtocolManager(gspec.Config, fastSync, NetworkId, 1000, evmux, &testTxPool{added: newtx}, pow, blockchain, db)
+	pm, err := NewProtocolManager(gspec.Config, fastSync, NetworkId, 1000, evmux, &testTxPool{added: newtx}, engine, blockchain, db)
 	if err != nil {
 		return nil, err
 	}
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index ccb7ec80b..987e14419 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -31,6 +31,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/syndtr/goleveldb/leveldb"
@@ -1378,7 +1378,7 @@ func (api *PublicDebugAPI) SeedHash(ctx context.Context, number uint64) (string,
 	if block == nil {
 		return "", fmt.Errorf("block #%d not found", number)
 	}
-	return fmt.Sprintf("0x%x", pow.EthashSeedHash(number)), nil
+	return fmt.Sprintf("0x%x", ethash.SeedHash(number)), nil
 }
 
 // PrivateDebugAPI is the collection of Etheruem APIs exposed over the private
diff --git a/les/backend.go b/les/backend.go
index d656cf41f..bb08efd91 100644
--- a/les/backend.go
+++ b/les/backend.go
@@ -25,6 +25,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/compiler"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/node"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	rpc "github.com/ethereum/go-ethereum/rpc"
 )
 
@@ -59,7 +59,7 @@ type LightEthereum struct {
 	ApiBackend *LesApiBackend
 
 	eventMux       *event.TypeMux
-	pow            pow.PoW
+	engine         consensus.Engine
 	accountManager *accounts.Manager
 	solcPath       string
 	solc           *compiler.Solidity
@@ -88,14 +88,12 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 		chainConfig:    chainConfig,
 		eventMux:       ctx.EventMux,
 		accountManager: ctx.AccountManager,
-		pow:            eth.CreatePoW(ctx, config),
+		engine:         eth.CreateConsensusEngine(ctx, config, chainConfig, chainDb),
 		shutdownChan:   make(chan bool),
 		netVersionId:   config.NetworkId,
 		solcPath:       config.SolcPath,
 	}
-
-	eth.blockchain, err = light.NewLightChain(odr, eth.chainConfig, eth.pow, eth.eventMux)
-	if err != nil {
+	if eth.blockchain, err = light.NewLightChain(odr, eth.chainConfig, eth.engine, eth.eventMux); err != nil {
 		return nil, err
 	}
 	// Rewind the chain in case of an incompatible config upgrade.
@@ -106,7 +104,7 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 	}
 
 	eth.txPool = light.NewTxPool(eth.chainConfig, eth.eventMux, eth.blockchain, eth.relay)
-	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.LightMode, config.NetworkId, eth.eventMux, eth.pow, eth.blockchain, nil, chainDb, odr, relay); err != nil {
+	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.LightMode, config.NetworkId, eth.eventMux, eth.engine, eth.blockchain, nil, chainDb, odr, relay); err != nil {
 		return nil, err
 	}
 	relay.ps = eth.protocolManager.peers
diff --git a/les/handler.go b/les/handler.go
index ece2060ee..fbb9e9906 100644
--- a/les/handler.go
+++ b/les/handler.go
@@ -27,6 +27,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/p2p/discv5"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 )
@@ -128,7 +128,7 @@ type ProtocolManager struct {
 
 // NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
 // with the ethereum network.
-func NewProtocolManager(chainConfig *params.ChainConfig, lightSync bool, networkId int, mux *event.TypeMux, pow pow.PoW, blockchain BlockChain, txpool txPool, chainDb ethdb.Database, odr *LesOdr, txrelay *LesTxRelay) (*ProtocolManager, error) {
+func NewProtocolManager(chainConfig *params.ChainConfig, lightSync bool, networkId int, mux *event.TypeMux, engine consensus.Engine, blockchain BlockChain, txpool txPool, chainDb ethdb.Database, odr *LesOdr, txrelay *LesTxRelay) (*ProtocolManager, error) {
 	// Create the protocol manager with the base fields
 	manager := &ProtocolManager{
 		lightSync:   lightSync,
diff --git a/les/helper_test.go b/les/helper_test.go
index f37bec80e..7e442c131 100644
--- a/les/helper_test.go
+++ b/les/helper_test.go
@@ -28,6 +28,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -39,7 +40,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 var (
@@ -134,10 +134,10 @@ func testRCL() RequestCostList {
 // channels for different events.
 func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *core.BlockGen)) (*ProtocolManager, ethdb.Database, *LesOdr, error) {
 	var (
-		evmux = new(event.TypeMux)
-		pow   = new(pow.FakePow)
-		db, _ = ethdb.NewMemDatabase()
-		gspec = core.Genesis{
+		evmux  = new(event.TypeMux)
+		engine = ethash.NewFaker()
+		db, _  = ethdb.NewMemDatabase()
+		gspec  = core.Genesis{
 			Config: params.TestChainConfig,
 			Alloc:  core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}},
 		}
@@ -148,9 +148,9 @@ func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *cor
 
 	if lightSync {
 		odr = NewLesOdr(db)
-		chain, _ = light.NewLightChain(odr, gspec.Config, pow, evmux)
+		chain, _ = light.NewLightChain(odr, gspec.Config, engine, evmux)
 	} else {
-		blockchain, _ := core.NewBlockChain(db, gspec.Config, pow, evmux, vm.Config{})
+		blockchain, _ := core.NewBlockChain(db, gspec.Config, engine, evmux, vm.Config{})
 		gchain, _ := core.GenerateChain(gspec.Config, genesis, db, blocks, generator)
 		if _, err := blockchain.InsertChain(gchain); err != nil {
 			panic(err)
@@ -158,7 +158,7 @@ func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *cor
 		chain = blockchain
 	}
 
-	pm, err := NewProtocolManager(gspec.Config, lightSync, NetworkId, evmux, pow, chain, nil, db, odr, nil)
+	pm, err := NewProtocolManager(gspec.Config, lightSync, NetworkId, evmux, engine, chain, nil, db, odr, nil)
 	if err != nil {
 		return nil, nil, nil, err
 	}
diff --git a/les/server.go b/les/server.go
index 5957add36..22fe59b7a 100644
--- a/les/server.go
+++ b/les/server.go
@@ -45,7 +45,7 @@ type LesServer struct {
 }
 
 func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
-	pm, err := NewProtocolManager(eth.BlockChain().Config(), false, config.NetworkId, eth.EventMux(), eth.Pow(), eth.BlockChain(), eth.TxPool(), eth.ChainDb(), nil, nil)
+	pm, err := NewProtocolManager(eth.BlockChain().Config(), false, config.NetworkId, eth.EventMux(), eth.Engine(), eth.BlockChain(), eth.TxPool(), eth.ChainDb(), nil, nil)
 	if err != nil {
 		return nil, err
 	}
diff --git a/light/lightchain.go b/light/lightchain.go
index 98fb024f0..4073e39e5 100644
--- a/light/lightchain.go
+++ b/light/lightchain.go
@@ -24,13 +24,13 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/hashicorp/golang-lru"
 )
@@ -64,14 +64,13 @@ type LightChain struct {
 	procInterrupt int32 // interrupt signaler for block processing
 	wg            sync.WaitGroup
 
-	pow       pow.PoW
-	validator core.HeaderValidator
+	engine consensus.Engine
 }
 
 // NewLightChain returns a fully initialised light chain using information
 // available in the database. It initialises the default Ethereum header
 // validator.
-func NewLightChain(odr OdrBackend, config *params.ChainConfig, pow pow.PoW, mux *event.TypeMux) (*LightChain, error) {
+func NewLightChain(odr OdrBackend, config *params.ChainConfig, engine consensus.Engine, mux *event.TypeMux) (*LightChain, error) {
 	bodyCache, _ := lru.New(bodyCacheLimit)
 	bodyRLPCache, _ := lru.New(bodyCacheLimit)
 	blockCache, _ := lru.New(blockCacheLimit)
@@ -84,21 +83,17 @@ func NewLightChain(odr OdrBackend, config *params.ChainConfig, pow pow.PoW, mux
 		bodyCache:    bodyCache,
 		bodyRLPCache: bodyRLPCache,
 		blockCache:   blockCache,
-		pow:          pow,
+		engine:       engine,
 	}
-
 	var err error
-	bc.hc, err = core.NewHeaderChain(odr.Database(), config, bc.Validator, bc.getProcInterrupt)
-	bc.SetValidator(core.NewHeaderValidator(config, bc.hc, pow))
+	bc.hc, err = core.NewHeaderChain(odr.Database(), config, bc.engine, bc.getProcInterrupt)
 	if err != nil {
 		return nil, err
 	}
-
 	bc.genesisBlock, _ = bc.GetBlockByNumber(NoOdr, 0)
 	if bc.genesisBlock == nil {
 		return nil, core.ErrNoGenesis
 	}
-
 	if bc.genesisBlock.Hash() == params.MainNetGenesisHash {
 		// add trusted CHT
 		WriteTrustedCht(bc.chainDb, TrustedCht{Number: 805, Root: common.HexToHash("85e4286fe0a730390245c49de8476977afdae0eb5530b277f62a52b12313d50f")})
@@ -145,9 +140,6 @@ func (self *LightChain) loadLastState() error {
 	headerTd := self.GetTd(header.Hash(), header.Number.Uint64())
 	log.Info("Loaded most recent local header", "number", header.Number, "hash", header.Hash(), "td", headerTd)
 
-	// Try to be smart and issue a pow verification for the head to pre-generate caches
-	go self.pow.Verify(types.NewBlockWithHeader(header))
-
 	return nil
 }
 
@@ -188,20 +180,6 @@ func (self *LightChain) Status() (td *big.Int, currentBlock common.Hash, genesis
 	return self.GetTd(hash, header.Number.Uint64()), hash, self.genesisBlock.Hash()
 }
 
-// SetValidator sets the validator which is used to validate incoming headers.
-func (self *LightChain) SetValidator(validator core.HeaderValidator) {
-	self.procmu.Lock()
-	defer self.procmu.Unlock()
-	self.validator = validator
-}
-
-// Validator returns the current header validator.
-func (self *LightChain) Validator() core.HeaderValidator {
-	self.procmu.RLock()
-	defer self.procmu.RUnlock()
-	return self.validator
-}
-
 // State returns a new mutable state based on the current HEAD block.
 func (self *LightChain) State() *LightState {
 	return NewLightState(StateTrieID(self.hc.CurrentHeader()), self.odr)
diff --git a/light/lightchain_test.go b/light/lightchain_test.go
index e9236f1fd..41010cf57 100644
--- a/light/lightchain_test.go
+++ b/light/lightchain_test.go
@@ -23,12 +23,12 @@ import (
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // So we can deterministically seed different blockchains
@@ -49,18 +49,15 @@ func makeHeaderChain(parent *types.Header, n int, db ethdb.Database, seed int) [
 	return headers
 }
 
-func testChainConfig() *params.ChainConfig {
-	return &params.ChainConfig{HomesteadBlock: big.NewInt(0)}
-}
-
 // newCanonical creates a chain database, and injects a deterministic canonical
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(n int) (ethdb.Database, *LightChain, error) {
 	db, _ := ethdb.NewMemDatabase()
-	gspec := core.Genesis{Config: testChainConfig()}
+	gspec := core.Genesis{Config: params.TestChainConfig}
 	genesis := gspec.MustCommit(db)
-	blockchain, _ := NewLightChain(&dummyOdr{db: db}, gspec.Config, pow.FakePow{}, new(event.TypeMux))
+	blockchain, _ := NewLightChain(&dummyOdr{db: db}, gspec.Config, ethash.NewFaker(), new(event.TypeMux))
+
 	// Create and inject the requested chain
 	if n == 0 {
 		return db, blockchain, nil
@@ -76,14 +73,13 @@ func newTestLightChain() *LightChain {
 	db, _ := ethdb.NewMemDatabase()
 	gspec := &core.Genesis{
 		Difficulty: big.NewInt(1),
-		Config:     testChainConfig(),
+		Config:     params.TestChainConfig,
 	}
 	gspec.MustCommit(db)
-	lc, err := NewLightChain(&dummyOdr{db: db}, gspec.Config, pow.NewTestEthash(), new(event.TypeMux))
+	lc, err := NewLightChain(&dummyOdr{db: db}, gspec.Config, ethash.NewFullFaker(), new(event.TypeMux))
 	if err != nil {
 		panic(err)
 	}
-	lc.SetValidator(bproc{})
 	return lc
 }
 
@@ -130,17 +126,17 @@ func printChain(bc *LightChain) {
 
 // testHeaderChainImport tries to process a chain of header, writing them into
 // the database if successful.
-func testHeaderChainImport(chain []*types.Header, LightChain *LightChain) error {
+func testHeaderChainImport(chain []*types.Header, lightchain *LightChain) error {
 	for _, header := range chain {
 		// Try and validate the header
-		if err := LightChain.Validator().ValidateHeader(header, LightChain.GetHeaderByHash(header.ParentHash), false); err != nil {
+		if err := lightchain.engine.VerifyHeader(lightchain.hc, header, true); err != nil {
 			return err
 		}
 		// Manually insert the header into the database, but don't reorganize (allows subsequent testing)
-		LightChain.mu.Lock()
-		core.WriteTd(LightChain.chainDb, header.Hash(), header.Number.Uint64(), new(big.Int).Add(header.Difficulty, LightChain.GetTdByHash(header.ParentHash)))
-		core.WriteHeader(LightChain.chainDb, header)
-		LightChain.mu.Unlock()
+		lightchain.mu.Lock()
+		core.WriteTd(lightchain.chainDb, header.Hash(), header.Number.Uint64(), new(big.Int).Add(header.Difficulty, lightchain.GetTdByHash(header.ParentHash)))
+		core.WriteHeader(lightchain.chainDb, header)
+		lightchain.mu.Unlock()
 	}
 	return nil
 }
@@ -257,10 +253,6 @@ func TestBrokenHeaderChain(t *testing.T) {
 	}
 }
 
-type bproc struct{}
-
-func (bproc) ValidateHeader(*types.Header, *types.Header, bool) error { return nil }
-
 func makeHeaderChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Header {
 	var chain []*types.Header
 	for i, difficulty := range d {
@@ -359,7 +351,7 @@ func TestReorgBadHeaderHashes(t *testing.T) {
 	defer func() { delete(core.BadHashes, headers[3].Hash()) }()
 
 	// Create a new LightChain and check that it rolled back the state.
-	ncm, err := NewLightChain(&dummyOdr{db: bc.chainDb}, testChainConfig(), pow.FakePow{}, new(event.TypeMux))
+	ncm, err := NewLightChain(&dummyOdr{db: bc.chainDb}, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux))
 	if err != nil {
 		t.Fatalf("failed to create new chain manager: %v", err)
 	}
diff --git a/light/odr_test.go b/light/odr_test.go
index 37d999994..ca33db246 100644
--- a/light/odr_test.go
+++ b/light/odr_test.go
@@ -26,6 +26,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -34,7 +35,6 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 )
@@ -248,7 +248,6 @@ func testChainGen(i int, block *core.BlockGen) {
 func testChainOdr(t *testing.T, protocol int, expFail uint64, fn odrTestFn) {
 	var (
 		evmux   = new(event.TypeMux)
-		pow     = new(pow.FakePow)
 		sdb, _  = ethdb.NewMemDatabase()
 		ldb, _  = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
@@ -256,16 +255,14 @@ func testChainOdr(t *testing.T, protocol int, expFail uint64, fn odrTestFn) {
 	)
 	gspec.MustCommit(ldb)
 	// Assemble the test environment
-	blockchain, _ := core.NewBlockChain(sdb, testChainConfig(), pow, evmux, vm.Config{})
-	chainConfig := &params.ChainConfig{HomesteadBlock: new(big.Int)}
-	gchain, _ := core.GenerateChain(chainConfig, genesis, sdb, 4, testChainGen)
+	blockchain, _ := core.NewBlockChain(sdb, params.TestChainConfig, ethash.NewFullFaker(), evmux, vm.Config{})
+	gchain, _ := core.GenerateChain(params.TestChainConfig, genesis, sdb, 4, testChainGen)
 	if _, err := blockchain.InsertChain(gchain); err != nil {
 		panic(err)
 	}
 
 	odr := &testOdr{sdb: sdb, ldb: ldb}
-	lightchain, _ := NewLightChain(odr, testChainConfig(), pow, evmux)
-	lightchain.SetValidator(bproc{})
+	lightchain, _ := NewLightChain(odr, params.TestChainConfig, ethash.NewFullFaker(), evmux)
 	headers := make([]*types.Header, len(gchain))
 	for i, block := range gchain {
 		headers[i] = block.Header()
diff --git a/light/txpool_test.go b/light/txpool_test.go
index 2b5fa7116..f23832a41 100644
--- a/light/txpool_test.go
+++ b/light/txpool_test.go
@@ -24,13 +24,13 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 type testTxRelay struct {
@@ -83,7 +83,6 @@ func TestTxPool(t *testing.T) {
 
 	var (
 		evmux   = new(event.TypeMux)
-		pow     = new(pow.FakePow)
 		sdb, _  = ethdb.NewMemDatabase()
 		ldb, _  = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
@@ -91,9 +90,8 @@ func TestTxPool(t *testing.T) {
 	)
 	gspec.MustCommit(ldb)
 	// Assemble the test environment
-	blockchain, _ := core.NewBlockChain(sdb, testChainConfig(), pow, evmux, vm.Config{})
-	chainConfig := &params.ChainConfig{HomesteadBlock: new(big.Int)}
-	gchain, _ := core.GenerateChain(chainConfig, genesis, sdb, poolTestBlocks, txPoolTestChainGen)
+	blockchain, _ := core.NewBlockChain(sdb, params.TestChainConfig, ethash.NewFullFaker(), evmux, vm.Config{})
+	gchain, _ := core.GenerateChain(params.TestChainConfig, genesis, sdb, poolTestBlocks, txPoolTestChainGen)
 	if _, err := blockchain.InsertChain(gchain); err != nil {
 		panic(err)
 	}
@@ -104,10 +102,9 @@ func TestTxPool(t *testing.T) {
 		discard: make(chan int, 1),
 		mined:   make(chan int, 1),
 	}
-	lightchain, _ := NewLightChain(odr, testChainConfig(), pow, evmux)
-	lightchain.SetValidator(bproc{})
+	lightchain, _ := NewLightChain(odr, params.TestChainConfig, ethash.NewFullFaker(), evmux)
 	txPermanent = 50
-	pool := NewTxPool(testChainConfig(), evmux, lightchain, relay)
+	pool := NewTxPool(params.TestChainConfig, evmux, lightchain, relay)
 	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 	defer cancel()
 
diff --git a/log/format.go b/log/format.go
index e315b5237..6c19c7a55 100644
--- a/log/format.go
+++ b/log/format.go
@@ -133,10 +133,10 @@ func TerminalFormat(usecolor bool) Format {
 			}
 		}
 		// try to justify the log output for short messages
-		if len(r.Ctx) > 0 && len(r.Msg) < termMsgJust {
-			b.Write(bytes.Repeat([]byte{' '}, termMsgJust-len(r.Msg)))
+		length := utf8.RuneCountInString(r.Msg)
+		if len(r.Ctx) > 0 && length < termMsgJust {
+			b.Write(bytes.Repeat([]byte{' '}, termMsgJust-length))
 		}
-
 		// print the keys logfmt style
 		logfmt(b, r.Ctx, color, true)
 		return b.Bytes()
diff --git a/miner/agent.go b/miner/agent.go
index 3c407f20b..855892a07 100644
--- a/miner/agent.go
+++ b/miner/agent.go
@@ -17,56 +17,49 @@
 package miner
 
 import (
-	"fmt"
 	"sync"
 
 	"sync/atomic"
 
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 type CpuAgent struct {
 	mu sync.Mutex
 
 	workCh        chan *Work
-	quit          chan struct{}
+	stop          chan struct{}
 	quitCurrentOp chan struct{}
 	returnCh      chan<- *Result
 
-	index int
-	pow   pow.PoW
+	chain  consensus.ChainReader
+	engine consensus.Engine
 
 	isMining int32 // isMining indicates whether the agent is currently mining
 }
 
-func NewCpuAgent(index int, pow pow.PoW) *CpuAgent {
+func NewCpuAgent(chain consensus.ChainReader, engine consensus.Engine) *CpuAgent {
 	miner := &CpuAgent{
-		pow:    pow,
-		index:  index,
-		quit:   make(chan struct{}),
+		chain:  chain,
+		engine: engine,
+		stop:   make(chan struct{}, 1),
 		workCh: make(chan *Work, 1),
 	}
-
 	return miner
 }
 
 func (self *CpuAgent) Work() chan<- *Work            { return self.workCh }
-func (self *CpuAgent) Pow() pow.PoW                  { return self.pow }
 func (self *CpuAgent) SetReturnCh(ch chan<- *Result) { self.returnCh = ch }
 
 func (self *CpuAgent) Stop() {
-	close(self.quit)
+	self.stop <- struct{}{}
 }
 
 func (self *CpuAgent) Start() {
-
 	if !atomic.CompareAndSwapInt32(&self.isMining, 0, 1) {
 		return // agent already started
 	}
-
 	go self.update()
 }
 
@@ -82,7 +75,7 @@ out:
 			self.quitCurrentOp = make(chan struct{})
 			go self.mine(work, self.quitCurrentOp)
 			self.mu.Unlock()
-		case <-self.quit:
+		case <-self.stop:
 			self.mu.Lock()
 			if self.quitCurrentOp != nil {
 				close(self.quitCurrentOp)
@@ -99,27 +92,27 @@ done:
 		select {
 		case <-self.workCh:
 		default:
-			close(self.workCh)
 			break done
 		}
 	}
-
 	atomic.StoreInt32(&self.isMining, 0)
 }
 
 func (self *CpuAgent) mine(work *Work, stop <-chan struct{}) {
-	log.Debug(fmt.Sprintf("(re)started agent[%d]. mining...\n", self.index))
-
-	// Mine
-	nonce, mixDigest := self.pow.Search(work.Block, stop)
-	if nonce != 0 {
-		block := work.Block.WithMiningResult(types.EncodeNonce(nonce), common.BytesToHash(mixDigest))
-		self.returnCh <- &Result{work, block}
+	if result, err := self.engine.Seal(self.chain, work.Block, stop); result != nil {
+		log.Info("Successfully sealed new block", "number", result.Number(), "hash", result.Hash())
+		self.returnCh <- &Result{work, result}
 	} else {
+		if err != nil {
+			log.Warn("Block sealing failed", "err", err)
+		}
 		self.returnCh <- nil
 	}
 }
 
 func (self *CpuAgent) GetHashRate() int64 {
-	return int64(self.pow.Hashrate())
+	if pow, ok := self.engine.(consensus.PoW); ok {
+		return int64(pow.Hashrate())
+	}
+	return 0
 }
diff --git a/miner/miner.go b/miner/miner.go
index dc0591b9a..453fff04d 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -24,6 +24,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -32,7 +33,6 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // Backend wraps all methods required for mining.
@@ -49,24 +49,24 @@ type Miner struct {
 
 	worker *worker
 
-	threads  int
 	coinbase common.Address
 	mining   int32
 	eth      Backend
-	pow      pow.PoW
+	engine   consensus.Engine
 
 	canStart    int32 // can start indicates whether we can start the mining operation
 	shouldStart int32 // should start indicates whether we should start after sync
 }
 
-func New(eth Backend, config *params.ChainConfig, mux *event.TypeMux, pow pow.PoW) *Miner {
+func New(eth Backend, config *params.ChainConfig, mux *event.TypeMux, engine consensus.Engine) *Miner {
 	miner := &Miner{
 		eth:      eth,
 		mux:      mux,
-		pow:      pow,
-		worker:   newWorker(config, common.Address{}, eth, mux),
+		engine:   engine,
+		worker:   newWorker(config, engine, common.Address{}, eth, mux),
 		canStart: 1,
 	}
+	miner.Register(NewCpuAgent(eth.BlockChain(), engine))
 	go miner.update()
 
 	return miner
@@ -86,7 +86,7 @@ out:
 			if self.Mining() {
 				self.Stop()
 				atomic.StoreInt32(&self.shouldStart, 1)
-				log.Info(fmt.Sprint("Mining operation aborted due to sync operation"))
+				log.Info("Mining aborted due to sync")
 			}
 		case downloader.DoneEvent, downloader.FailedEvent:
 			shouldStart := atomic.LoadInt32(&self.shouldStart) == 1
@@ -94,7 +94,7 @@ out:
 			atomic.StoreInt32(&self.canStart, 1)
 			atomic.StoreInt32(&self.shouldStart, 0)
 			if shouldStart {
-				self.Start(self.coinbase, self.threads)
+				self.Start(self.coinbase)
 			}
 			// unsubscribe. we're only interested in this event once
 			events.Unsubscribe()
@@ -116,23 +116,18 @@ func (m *Miner) SetGasPrice(price *big.Int) {
 	m.worker.setGasPrice(price)
 }
 
-func (self *Miner) Start(coinbase common.Address, threads int) {
+func (self *Miner) Start(coinbase common.Address) {
 	atomic.StoreInt32(&self.shouldStart, 1)
 	self.worker.setEtherbase(coinbase)
 	self.coinbase = coinbase
-	self.threads = threads
 
 	if atomic.LoadInt32(&self.canStart) == 0 {
-		log.Info(fmt.Sprint("Can not start mining operation due to network sync (starts when finished)"))
+		log.Info("Network syncing, will start miner afterwards")
 		return
 	}
 	atomic.StoreInt32(&self.mining, 1)
 
-	for i := 0; i < threads; i++ {
-		self.worker.register(NewCpuAgent(i, self.pow))
-	}
-
-	log.Info(fmt.Sprintf("Starting mining operation (CPU=%d TOT=%d)\n", threads, len(self.worker.agents)))
+	log.Info("Starting mining operation")
 	self.worker.start()
 	self.worker.commitNewWork()
 }
@@ -159,7 +154,9 @@ func (self *Miner) Mining() bool {
 }
 
 func (self *Miner) HashRate() (tot int64) {
-	tot += int64(self.pow.Hashrate())
+	if pow, ok := self.engine.(consensus.PoW); ok {
+		tot += int64(pow.Hashrate())
+	}
 	// do we care this might race? is it worth we're rewriting some
 	// aspects of the worker/locking up agents so we can get an accurate
 	// hashrate?
diff --git a/miner/remote_agent.go b/miner/remote_agent.go
index 08c5fc6f0..bb223ba1b 100644
--- a/miner/remote_agent.go
+++ b/miner/remote_agent.go
@@ -18,16 +18,16 @@ package miner
 
 import (
 	"errors"
-	"fmt"
 	"math/big"
 	"sync"
 	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 type hashrate struct {
@@ -42,7 +42,8 @@ type RemoteAgent struct {
 	workCh   chan *Work
 	returnCh chan<- *Result
 
-	pow         pow.PoW
+	chain       consensus.ChainReader
+	engine      consensus.Engine
 	currentWork *Work
 	work        map[common.Hash]*Work
 
@@ -52,9 +53,10 @@ type RemoteAgent struct {
 	running int32 // running indicates whether the agent is active. Call atomically
 }
 
-func NewRemoteAgent(pow pow.PoW) *RemoteAgent {
+func NewRemoteAgent(chain consensus.ChainReader, engine consensus.Engine) *RemoteAgent {
 	return &RemoteAgent{
-		pow:      pow,
+		chain:    chain,
+		engine:   engine,
 		work:     make(map[common.Hash]*Work),
 		hashrate: make(map[common.Hash]hashrate),
 	}
@@ -114,7 +116,7 @@ func (a *RemoteAgent) GetWork() ([3]string, error) {
 		block := a.currentWork.Block
 
 		res[0] = block.HashNoNonce().Hex()
-		seedHash := pow.EthashSeedHash(block.NumberU64())
+		seedHash := ethash.SeedHash(block.NumberU64())
 		res[1] = common.BytesToHash(seedHash).Hex()
 		// Calculate the "target" to be returned to the external miner
 		n := big.NewInt(1)
@@ -129,8 +131,8 @@ func (a *RemoteAgent) GetWork() ([3]string, error) {
 	return res, errors.New("No work available yet, don't panic.")
 }
 
-// SubmitWork tries to inject a PoW solution tinto the remote agent, returning
-// whether the solution was acceted or not (not can be both a bad PoW as well as
+// SubmitWork tries to inject a pow solution into the remote agent, returning
+// whether the solution was accepted or not (not can be both a bad pow as well as
 // any other error, like no work pending).
 func (a *RemoteAgent) SubmitWork(nonce types.BlockNonce, mixDigest, hash common.Hash) bool {
 	a.mu.Lock()
@@ -139,15 +141,20 @@ func (a *RemoteAgent) SubmitWork(nonce types.BlockNonce, mixDigest, hash common.
 	// Make sure the work submitted is present
 	work := a.work[hash]
 	if work == nil {
-		log.Info(fmt.Sprintf("Work was submitted for %x but no pending work found", hash))
+		log.Info("Work submitted but none pending", "hash", hash)
 		return false
 	}
-	// Make sure the PoW solutions is indeed valid
-	block := work.Block.WithMiningResult(nonce, mixDigest)
-	if err := a.pow.Verify(block); err != nil {
-		log.Warn(fmt.Sprintf("Invalid PoW submitted for %x: %v", hash, err))
+	// Make sure the Engine solutions is indeed valid
+	result := work.Block.Header()
+	result.Nonce = nonce
+	result.MixDigest = mixDigest
+
+	if err := a.engine.VerifySeal(a.chain, result); err != nil {
+		log.Warn("Invalid proof-of-work submitted", "hash", hash, "err", err)
 		return false
 	}
+	block := work.Block.WithSeal(result)
+
 	// Solutions seems to be valid, return to the miner and notify acceptance
 	a.returnCh <- &Result{work, block}
 	delete(a.work, hash)
diff --git a/miner/unconfirmed.go b/miner/unconfirmed.go
index bb7d0ff26..ee52d8512 100644
--- a/miner/unconfirmed.go
+++ b/miner/unconfirmed.go
@@ -18,7 +18,6 @@ package miner
 
 import (
 	"container/ring"
-	"fmt"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -80,7 +79,7 @@ func (set *unconfirmedBlocks) Insert(index uint64, hash common.Hash) {
 		set.blocks.Move(-1).Link(item)
 	}
 	// Display a log for the user to notify of a new mined block unconfirmed
-	log.Info(fmt.Sprintf("🔨  mined potential block #%d [%x…], waiting for %d blocks to confirm", index, hash.Bytes()[:4], set.depth))
+	log.Info("🔨 mined potential block", "number", index, "hash", hash)
 }
 
 // Shift drops all unconfirmed blocks from the set which exceed the unconfirmed sets depth
@@ -100,11 +99,11 @@ func (set *unconfirmedBlocks) Shift(height uint64) {
 		header := set.chain.GetHeaderByNumber(next.index)
 		switch {
 		case header == nil:
-			log.Warn(fmt.Sprintf("failed to retrieve header of mined block #%d [%x…]", next.index, next.hash.Bytes()[:4]))
+			log.Warn("Failed to retrieve header of mined block", "number", next.index, "hash", next.hash)
 		case header.Hash() == next.hash:
-			log.Info(fmt.Sprintf("🔗  mined block #%d [%x…] reached canonical chain", next.index, next.hash.Bytes()[:4]))
+			log.Info("🔗 block reached canonical chain", "number", next.index, "hash", next.hash)
 		default:
-			log.Info(fmt.Sprintf("⑂ mined block #%d [%x…] became a side fork", next.index, next.hash.Bytes()[:4]))
+			log.Info("⑂ block  became a side fork", "number", next.index, "hash", next.hash)
 		}
 		// Drop the block out of the ring
 		if set.blocks.Value == set.blocks.Next().Value {
diff --git a/miner/worker.go b/miner/worker.go
index 2f090924e..347de4e08 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -26,6 +26,8 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -34,7 +36,6 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"gopkg.in/fatih/set.v0"
 )
 
@@ -84,6 +85,7 @@ type Result struct {
 // worker is the main object which takes care of applying messages to the new state
 type worker struct {
 	config *params.ChainConfig
+	engine consensus.Engine
 
 	mu sync.Mutex
 
@@ -94,7 +96,6 @@ type worker struct {
 
 	agents map[Agent]struct{}
 	recv   chan *Result
-	pow    pow.PoW
 
 	eth     Backend
 	chain   *core.BlockChain
@@ -123,9 +124,10 @@ type worker struct {
 	fullValidation bool
 }
 
-func newWorker(config *params.ChainConfig, coinbase common.Address, eth Backend, mux *event.TypeMux) *worker {
+func newWorker(config *params.ChainConfig, engine consensus.Engine, coinbase common.Address, eth Backend, mux *event.TypeMux) *worker {
 	worker := &worker{
 		config:         config,
+		engine:         engine,
 		eth:            eth,
 		mux:            mux,
 		chainDb:        eth.ChainDb(),
@@ -209,16 +211,10 @@ func (self *worker) stop() {
 	self.mu.Lock()
 	defer self.mu.Unlock()
 	if atomic.LoadInt32(&self.mining) == 1 {
-		// Stop all agents.
 		for agent := range self.agents {
 			agent.Stop()
-			// Remove CPU agents.
-			if _, ok := agent.(*CpuAgent); ok {
-				delete(self.agents, agent)
-			}
 		}
 	}
-
 	atomic.StoreInt32(&self.mining, 0)
 	atomic.StoreInt32(&self.atWork, 0)
 }
@@ -277,7 +273,7 @@ func (self *worker) wait() {
 
 			if self.fullValidation {
 				if _, err := self.chain.InsertChain(types.Blocks{block}); err != nil {
-					log.Error(fmt.Sprint("mining err", err))
+					log.Error("Mined invalid block", "err", err)
 					continue
 				}
 				go self.mux.Post(core.NewMinedBlockEvent{Block: block})
@@ -285,19 +281,16 @@ func (self *worker) wait() {
 				work.state.Commit(self.config.IsEIP158(block.Number()))
 				parent := self.chain.GetBlock(block.ParentHash(), block.NumberU64()-1)
 				if parent == nil {
-					log.Error(fmt.Sprint("Invalid block found during mining"))
+					log.Error("Invalid block found during mining")
 					continue
 				}
-
-				auxValidator := self.eth.BlockChain().AuxValidator()
-				if err := core.ValidateHeader(self.config, auxValidator, block.Header(), parent.Header(), true, false); err != nil && err != core.BlockFutureErr {
-					log.Error(fmt.Sprint("Invalid header on mined block:", err))
+				if err := self.engine.VerifyHeader(self.chain, block.Header(), false); err != nil {
+					log.Error("Invalid header on mined block", "err", err)
 					continue
 				}
-
 				stat, err := self.chain.WriteBlock(block)
 				if err != nil {
-					log.Error(fmt.Sprint("error writing block to chain", err))
+					log.Error("Failed writing block to chain", "err", err)
 					continue
 				}
 
@@ -333,7 +326,7 @@ func (self *worker) wait() {
 						self.mux.Post(logs)
 					}
 					if err := core.WriteBlockReceipts(self.chainDb, block.Hash(), block.NumberU64(), receipts); err != nil {
-						log.Warn(fmt.Sprint("error writing block receipts:", err))
+						log.Warn("Failed writing block receipts", "err", err)
 					}
 				}(block, work.state.Logs(), work.receipts)
 			}
@@ -424,9 +417,9 @@ func (self *worker) commitNewWork() {
 		tstamp = parent.Time().Int64() + 1
 	}
 	// this will ensure we're not going off too far in the future
-	if now := time.Now().Unix(); tstamp > now+4 {
+	if now := time.Now().Unix(); tstamp > now+1 {
 		wait := time.Duration(tstamp-now) * time.Second
-		log.Info(fmt.Sprint("We are too far in the future. Waiting for", wait))
+		log.Info("Mining too far in the future", "wait", common.PrettyDuration(wait))
 		time.Sleep(wait)
 	}
 
@@ -434,13 +427,19 @@ func (self *worker) commitNewWork() {
 	header := &types.Header{
 		ParentHash: parent.Hash(),
 		Number:     num.Add(num, common.Big1),
-		Difficulty: core.CalcDifficulty(self.config, uint64(tstamp), parent.Time().Uint64(), parent.Number(), parent.Difficulty()),
 		GasLimit:   core.CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
-		Coinbase:   self.coinbase,
 		Extra:      self.extra,
 		Time:       big.NewInt(tstamp),
 	}
+	// Only set the coinbase if we are mining (avoid spurious block rewards)
+	if atomic.LoadInt32(&self.mining) == 1 {
+		header.Coinbase = self.coinbase
+	}
+	if err := self.engine.Prepare(self.chain, header); err != nil {
+		log.Error("Failed to prepare header for mining", "err", err)
+		return
+	}
 	// If we are care about TheDAO hard-fork check whether to override the extra-data or not
 	if daoBlock := self.config.DAOForkBlock; daoBlock != nil {
 		// Check whether the block is among the fork extra-override range
@@ -457,21 +456,19 @@ func (self *worker) commitNewWork() {
 	// Could potentially happen if starting to mine in an odd state.
 	err := self.makeCurrent(parent, header)
 	if err != nil {
-		log.Info(fmt.Sprint("Could not create new env for mining, retrying on next block."))
+		log.Error("Failed to create mining context", "err", err)
 		return
 	}
 	// Create the current work task and check any fork transitions needed
 	work := self.current
 	if self.config.DAOForkSupport && self.config.DAOForkBlock != nil && self.config.DAOForkBlock.Cmp(header.Number) == 0 {
-		core.ApplyDAOHardFork(work.state)
+		misc.ApplyDAOHardFork(work.state)
 	}
-
 	pending, err := self.eth.TxPool().Pending()
 	if err != nil {
-		log.Error(fmt.Sprintf("Could not fetch pending transactions: %v", err))
+		log.Error("Failed to fetch pending transactions", "err", err)
 		return
 	}
-
 	txs := types.NewTransactionsByPriceAndNonce(pending)
 	work.commitTransactions(self.mux, txs, self.gasPrice, self.chain)
 
@@ -488,31 +485,26 @@ func (self *worker) commitNewWork() {
 			break
 		}
 		if err := self.commitUncle(work, uncle.Header()); err != nil {
-			log.Trace(fmt.Sprintf("Bad uncle found and will be removed (%x)\n", hash[:4]))
+			log.Trace("Bad uncle found and will be removed", "hash", hash)
 			log.Trace(fmt.Sprint(uncle))
 
 			badUncles = append(badUncles, hash)
 		} else {
-			log.Debug(fmt.Sprintf("committing %x as uncle\n", hash[:4]))
+			log.Debug("Committing new uncle to block", "hash", hash)
 			uncles = append(uncles, uncle.Header())
 		}
 	}
 	for _, hash := range badUncles {
 		delete(self.possibleUncles, hash)
 	}
-
-	if atomic.LoadInt32(&self.mining) == 1 {
-		// commit state root after all state transitions.
-		core.AccumulateRewards(work.state, header, uncles)
-		header.Root = work.state.IntermediateRoot(self.config.IsEIP158(header.Number))
+	// Create the new block to seal with the consensus engine
+	if work.Block, err = self.engine.Finalize(self.chain, header, work.state, work.txs, uncles, work.receipts); err != nil {
+		log.Error("Failed to finalize block for sealing", "err", err)
+		return
 	}
-
-	// create the new block whose nonce will be mined.
-	work.Block = types.NewBlock(header, work.txs, uncles, work.receipts)
-
 	// We only care about logging if we're actually mining.
 	if atomic.LoadInt32(&self.mining) == 1 {
-		log.Info(fmt.Sprintf("commit new work on block %v with %d txs & %d uncles. Took %v\n", work.Block.Number(), work.tcount, len(uncles), time.Since(tstart)))
+		log.Info("Commit new mining work", "number", work.Block.Number(), "txs", work.tcount, "uncles", len(uncles), "elapsed", common.PrettyDuration(time.Since(tstart)))
 		self.unconfirmed.Shift(work.Block.NumberU64() - 1)
 	}
 	self.push(work)
@@ -521,13 +513,13 @@ func (self *worker) commitNewWork() {
 func (self *worker) commitUncle(work *Work, uncle *types.Header) error {
 	hash := uncle.Hash()
 	if work.uncles.Has(hash) {
-		return core.UncleError("Uncle not unique")
+		return core.UncleError("uncle not unique")
 	}
 	if !work.ancestors.Has(uncle.ParentHash) {
-		return core.UncleError(fmt.Sprintf("Uncle's parent unknown (%x)", uncle.ParentHash[0:4]))
+		return core.UncleError(fmt.Sprintf("uncle's parent unknown (%x)", uncle.ParentHash[0:4]))
 	}
 	if work.family.Has(hash) {
-		return core.UncleError(fmt.Sprintf("Uncle already in family (%x)", hash))
+		return core.UncleError(fmt.Sprintf("uncle already in family (%x)", hash))
 	}
 	work.uncles.Add(uncle.Hash())
 	return nil
@@ -552,7 +544,7 @@ func (env *Work) commitTransactions(mux *event.TypeMux, txs *types.TransactionsB
 		// Check whether the tx is replay protected. If we're not in the EIP155 hf
 		// phase, start ignoring the sender until we do.
 		if tx.Protected() && !env.config.IsEIP155(env.header.Number) {
-			log.Trace(fmt.Sprintf("Transaction (%x) is replay protected, but we haven't yet hardforked. Transaction will be ignored until we hardfork.\n", tx.Hash()))
+			log.Trace("Ignoring reply protected transaction", "hash", tx.Hash(), "eip155", env.config.EIP155Block)
 
 			txs.Pop()
 			continue
@@ -561,7 +553,7 @@ func (env *Work) commitTransactions(mux *event.TypeMux, txs *types.TransactionsB
 		// Ignore any transactions (and accounts subsequently) with low gas limits
 		if tx.GasPrice().Cmp(gasPrice) < 0 && !env.ownedAccounts.Has(from) {
 			// Pop the current low-priced transaction without shifting in the next from the account
-			log.Info(fmt.Sprintf("Transaction (%x) below gas price (tx=%dwei ask=%dwei). All sequential txs from this address(%x) will be ignored\n", tx.Hash().Bytes()[:4], tx.GasPrice(), gasPrice, from[:4]))
+			log.Warn("Transaction below gas price", "sender", from, "hash", tx.Hash(), "have", tx.GasPrice(), "want", gasPrice)
 
 			env.lowGasTxs = append(env.lowGasTxs, tx)
 			txs.Pop()
@@ -575,12 +567,12 @@ func (env *Work) commitTransactions(mux *event.TypeMux, txs *types.TransactionsB
 		switch {
 		case core.IsGasLimitErr(err):
 			// Pop the current out-of-gas transaction without shifting in the next from the account
-			log.Trace(fmt.Sprintf("Gas limit reached for (%x) in this block. Continue to try smaller txs\n", from[:4]))
+			log.Trace("Gas limit exceeded for current block", "sender", from)
 			txs.Pop()
 
 		case err != nil:
 			// Pop the current failed transaction without shifting in the next from the account
-			log.Trace(fmt.Sprintf("Transaction (%x) failed, will be removed: %v\n", tx.Hash().Bytes()[:4], err))
+			log.Trace("Transaction failed, will be removed", "hash", tx.Hash(), "err", err)
 			env.failedTxs = append(env.failedTxs, tx)
 			txs.Pop()
 
diff --git a/params/util.go b/params/util.go
index 546ebb35c..bf833d510 100644
--- a/params/util.go
+++ b/params/util.go
@@ -38,6 +38,6 @@ var (
 	TestNetSpuriousDragon = big.NewInt(10)
 	MainNetSpuriousDragon = big.NewInt(2675000)
 
-	TestNetChainID = big.NewInt(3) // Test net default chain ID
-	MainNetChainID = big.NewInt(1) // main net default chain ID
+	TestNetChainID = big.NewInt(3) // Testnet default chain ID
+	MainNetChainID = big.NewInt(1) // Mainnet default chain ID
 )
diff --git a/pow/pow.go b/pow/pow.go
deleted file mode 100644
index 4849adb3e..000000000
--- a/pow/pow.go
+++ /dev/null
@@ -1,58 +0,0 @@
-// Copyright 2014 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package pow
-
-import (
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
-)
-
-type Block interface {
-	Difficulty() *big.Int
-	HashNoNonce() common.Hash
-	Nonce() uint64
-	MixDigest() common.Hash
-	NumberU64() uint64
-}
-
-type ChainManager interface {
-	GetBlockByNumber(uint64) *types.Block
-	CurrentBlock() *types.Block
-}
-
-type PoW interface {
-	Verify(block Block) error
-	Search(block Block, stop <-chan struct{}) (uint64, []byte)
-	Hashrate() float64
-}
-
-// FakePow is a non-validating proof of work implementation.
-// It returns true from Verify for any block.
-type FakePow struct{}
-
-// Verify implements PoW, returning a success for an input.
-func (pow FakePow) Verify(block Block) error { return nil }
-
-// Search implements PoW, returning the nonce 0 for any call.
-func (pow FakePow) Search(block Block, stop <-chan struct{}) (uint64, []byte) {
-	return 0, nil
-}
-
-// Hashrate implements PoW, returning 0.
-func (pow FakePow) Hashrate() float64 { return 0 }
diff --git a/tests/block_test_util.go b/tests/block_test_util.go
index 456a4ccb8..b9678a77b 100644
--- a/tests/block_test_util.go
+++ b/tests/block_test_util.go
@@ -27,6 +27,7 @@ import (
 	"strings"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -35,7 +36,6 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
@@ -172,7 +172,7 @@ func runBlockTest(homesteadBlock, daoForkBlock, gasPriceFork *big.Int, test *Blo
 	core.WriteHeadBlockHash(db, test.Genesis.Hash())
 	evmux := new(event.TypeMux)
 	config := &params.ChainConfig{HomesteadBlock: homesteadBlock, DAOForkBlock: daoForkBlock, DAOForkSupport: true, EIP150Block: gasPriceFork}
-	chain, err := core.NewBlockChain(db, config, pow.NewSharedEthash(), evmux, vm.Config{})
+	chain, err := core.NewBlockChain(db, config, ethash.NewShared(), evmux, vm.Config{})
 	if err != nil {
 		return err
 	}
diff --git a/trie/iterator.go b/trie/iterator.go
index 234c49ecc..ddc674d2b 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -18,6 +18,7 @@ package trie
 
 import (
 	"bytes"
+
 	"github.com/ethereum/go-ethereum/common"
 )