dex: implement recovery mechanism (#258)

* dex: implement recovery mechanism

The DEXON recovery protocol allows us to use the Ethereum blockchain as a
fallback consensus chain to coordinate recovery.

* fix

32 files changed, 2435 insertions, 435 deletions

diff --git a/cmd/gdex/main.go b/cmd/gdex/main.go
index dcd46e796..29b61a4ec 100644
--- a/cmd/gdex/main.go
+++ b/cmd/gdex/main.go
@@ -140,6 +140,7 @@ var (
 		utils.IndexerEnableFlag,
 		utils.IndexerPluginFlag,
 		utils.IndexerPluginFlagsFlag,
+		utils.RecoveryNetworkRPCFlag,
 		configFileFlag,
 	}
 
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index c6d60d0bb..6b0c682a7 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -664,6 +664,13 @@ var (
 		Usage: "External indexer plugin's flags if needed",
 		Value: "",
 	}
+
+	// Dexcon settings.
+	RecoveryNetworkRPCFlag = cli.StringFlag{
+		Name:  "recovery.network-rpc",
+		Usage: "RPC URL of the recovery network",
+		Value: "https://mainnet.infura.io",
+	}
 )
 
 // MakeDataDir retrieves the currently requested data directory, terminating
@@ -1257,27 +1264,41 @@ func SetDexConfig(ctx *cli.Context, stack *node.Node, cfg *dex.Config) {
 		cfg.RPCGasCap = new(big.Int).SetUint64(ctx.GlobalUint64(RPCGlobalGasCap.Name))
 	}
 
+	cfg.RecoveryNetworkRPC = ctx.GlobalString(RecoveryNetworkRPCFlag.Name)
+
 	// Override any default configs for hard coded networks.
 	switch {
 	case ctx.GlobalBool(TestnetFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 238
 		}
+		if !ctx.GlobalIsSet(RecoveryNetworkRPCFlag.Name) {
+			cfg.RecoveryNetworkRPC = "http://rinkeby.infura.io"
+		}
 		cfg.Genesis = core.DefaultTestnetGenesisBlock()
 	case ctx.GlobalBool(TaipeiFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 239
 		}
+		if !ctx.GlobalIsSet(RecoveryNetworkRPCFlag.Name) {
+			cfg.RecoveryNetworkRPC = "http://rinkeby.infura.io"
+		}
 		cfg.Genesis = core.DefaultTaipeiGenesisBlock()
 	case ctx.GlobalBool(YilanFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 240
 		}
+		if !ctx.GlobalIsSet(RecoveryNetworkRPCFlag.Name) {
+			cfg.RecoveryNetworkRPC = "http://rinkeby.infura.io"
+		}
 		cfg.Genesis = core.DefaultYilanGenesisBlock()
 	case ctx.GlobalBool(DeveloperFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 1337
 		}
+		if !ctx.GlobalIsSet(RecoveryNetworkRPCFlag.Name) {
+			cfg.RecoveryNetworkRPC = "http://rinkeby.infura.io"
+		}
 		// Create new developer account or reuse existing one
 		var (
 			developer accounts.Account
diff --git a/core/vm/oracle_contracts.go b/core/vm/oracle_contracts.go
index 37e734a5f..d983cdfc8 100644
--- a/core/vm/oracle_contracts.go
+++ b/core/vm/oracle_contracts.go
@@ -95,7 +95,7 @@ func publicKeyToNodeKeyAddress(pkBytes []byte) (common.Address, error) {
 	return crypto.PubkeyToAddress(*pk), nil
 }
 
-func idToAddress(id coreTypes.NodeID) common.Address {
+func IdToAddress(id coreTypes.NodeID) common.Address {
 	return common.BytesToAddress(id.Hash[12:])
 }
 
@@ -517,7 +517,7 @@ func (s *GovernanceState) DeleteNodeOffsets(n *nodeInfo) error {
 }
 
 func (s *GovernanceState) GetNodeByID(id coreTypes.NodeID) (*nodeInfo, error) {
-	offset := s.NodesOffsetByNodeKeyAddress(idToAddress(id))
+	offset := s.NodesOffsetByNodeKeyAddress(IdToAddress(id))
 	if offset.Cmp(big.NewInt(0)) < 0 {
 		return nil, errors.New("node not found")
 	}
@@ -630,7 +630,7 @@ func (s *GovernanceState) PutDKGMPKReady(addr common.Address, ready bool) {
 }
 func (s *GovernanceState) ClearDKGMPKReady(dkgSet map[coreTypes.NodeID]struct{}) {
 	for id := range dkgSet {
-		s.PutDKGMPKReady(idToAddress(id), false)
+		s.PutDKGMPKReady(IdToAddress(id), false)
 	}
 }
 
@@ -661,7 +661,7 @@ func (s *GovernanceState) PutDKGFinalized(addr common.Address, finalized bool) {
 }
 func (s *GovernanceState) ClearDKGFinalized(dkgSet map[coreTypes.NodeID]struct{}) {
 	for id := range dkgSet {
-		s.PutDKGFinalized(idToAddress(id), false)
+		s.PutDKGFinalized(IdToAddress(id), false)
 	}
 }
 
diff --git a/core/vm/oracle_contracts_test.go b/core/vm/oracle_contracts_test.go
index 4539f0864..6e2a7fc7f 100644
--- a/core/vm/oracle_contracts_test.go
+++ b/core/vm/oracle_contracts_test.go
@@ -933,7 +933,7 @@ func (g *OracleContractsTestSuite) TestResetDKG() {
 		dkgSets[round] = dkgSet
 
 		for id := range dkgSet {
-			offset := g.s.NodesOffsetByNodeKeyAddress(idToAddress(id))
+			offset := g.s.NodesOffsetByNodeKeyAddress(IdToAddress(id))
 			if offset.Cmp(big.NewInt(0)) < 0 {
 				panic("DKG node does not exist")
 			}
diff --git a/dex/backend.go b/dex/backend.go
index 056a6d221..6ee1a5fa1 100644
--- a/dex/backend.go
+++ b/dex/backend.go
@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/dexon-foundation/dexon-consensus/core/syncer"
 	"github.com/dexon-foundation/dexon/accounts"
 	"github.com/dexon-foundation/dexon/consensus"
 	"github.com/dexon-foundation/dexon/consensus/dexcon"
@@ -180,7 +181,12 @@ func New(ctx *node.ServiceContext, config *Config) (*Dexon, error) {
 	dex.protocolManager = pm
 	dex.network = NewDexconNetwork(pm)
 
-	dex.bp = NewBlockProposer(dex, dMoment)
+	recovery := NewRecovery(chainConfig.Recovery, config.RecoveryNetworkRPC,
+		dex.governance, config.PrivateKey)
+	watchCat := syncer.NewWatchCat(recovery, dex.governance, 10*time.Second,
+		time.Duration(chainConfig.Recovery.Timeout)*time.Second, log.Root())
+
+	dex.bp = NewBlockProposer(dex, watchCat, dMoment)
 	return dex, nil
 }
 
diff --git a/dex/blockproposer.go b/dex/blockproposer.go
index ad8b4c2b0..6c1de818a 100644
--- a/dex/blockproposer.go
+++ b/dex/blockproposer.go
@@ -24,16 +24,18 @@ type blockProposer struct {
 	syncing   int32
 	proposing int32
 	dex       *Dexon
+	watchCat  *syncer.WatchCat
 	dMoment   time.Time
 
 	wg     sync.WaitGroup
 	stopCh chan struct{}
 }
 
-func NewBlockProposer(dex *Dexon, dMoment time.Time) *blockProposer {
+func NewBlockProposer(dex *Dexon, watchCat *syncer.WatchCat, dMoment time.Time) *blockProposer {
 	return &blockProposer{
-		dex:     dex,
-		dMoment: dMoment,
+		dex:      dex,
+		watchCat: watchCat,
+		dMoment:  dMoment,
 	}
 }
 
@@ -116,9 +118,21 @@ func (b *blockProposer) syncConsensus() (*dexCore.Consensus, error) {
 	consensusSync := syncer.NewConsensus(b.dMoment, b.dex.app, b.dex.governance,
 		db, b.dex.network, privkey, log.Root())
 
+	// Start the watchCat.
+	log.Info("Starting sync watchCat ...")
+	b.watchCat.Start()
+
+	// Feed the current block we have in local blockchain.
+	cb := b.dex.blockchain.CurrentBlock()
+	var block coreTypes.Block
+	if err := rlp.DecodeBytes(cb.Header().DexconMeta, &block); err != nil {
+		panic(err)
+	}
+	b.watchCat.Feed(block.Position)
+
 	blocksToSync := func(coreHeight, height uint64) []*coreTypes.Block {
 		var blocks []*coreTypes.Block
-		for len(blocks) < 1024 && coreHeight < height {
+		for coreHeight < height {
 			var block coreTypes.Block
 			b := b.dex.blockchain.GetBlockByNumber(coreHeight + 1)
 			if err := rlp.DecodeBytes(b.Header().DexconMeta, &block); err != nil {
@@ -143,6 +157,7 @@ Loop:
 		if len(blocks) == 0 {
 			break Loop
 		}
+		b.watchCat.Feed(blocks[len(blocks)-1].Position)
 
 		log.Debug("Filling compaction chain", "num", len(blocks),
 			"first", blocks[0].Finalization.Height,
@@ -172,6 +187,8 @@ ListenLoop:
 		select {
 		case ev := <-ch:
 			blocks := blocksToSync(coreHeight, ev.Block.NumberU64())
+			b.watchCat.Feed(blocks[len(blocks)-1].Position)
+
 			if len(blocks) > 0 {
 				log.Debug("Filling compaction chain", "num", len(blocks),
 					"first", blocks[0].Finalization.Height,
@@ -193,8 +210,13 @@ ListenLoop:
 		case <-b.stopCh:
 			log.Debug("Early stop, before consensus core can run")
 			return nil, errors.New("early stop")
+		case <-b.watchCat.Meow():
+			log.Info("WatchCat signaled to stop syncing")
+			consensusSync.ForceSync(true)
+			break ListenLoop
 		}
 	}
 
+	b.watchCat.Stop()
 	return consensusSync.GetSyncedConsensus()
 }
diff --git a/dex/config.go b/dex/config.go
index 7661907cc..d218b35e2 100644
--- a/dex/config.go
+++ b/dex/config.go
@@ -126,4 +126,7 @@ type Config struct {
 
 	// Indexer config
 	Indexer indexer.Config
+
+	// Recovery network RPC
+	RecoveryNetworkRPC string
 }
diff --git a/dex/governance.go b/dex/governance.go
index d9cf8fb65..35c5b4174 100644
--- a/dex/governance.go
+++ b/dex/governance.go
@@ -263,6 +263,19 @@ func (d *DexconGovernance) NotarySet(round uint64) (map[string]struct{}, error)
 	return r, nil
 }
 
+func (d *DexconGovernance) NotarySetAddresses(round uint64) (map[common.Address]struct{}, error) {
+	notarySet, err := d.nodeSetCache.GetNotarySet(round)
+	if err != nil {
+		return nil, err
+	}
+
+	r := make(map[common.Address]struct{}, len(notarySet))
+	for id := range notarySet {
+		r[vm.IdToAddress(id)] = struct{}{}
+	}
+	return r, nil
+}
+
 func (d *DexconGovernance) DKGSet(round uint64) (map[string]struct{}, error) {
 	dkgSet, err := d.nodeSetCache.GetDKGSet(round)
 	if err != nil {
diff --git a/dex/recovery.go b/dex/recovery.go
new file mode 100644
index 000000000..cfc8ae203
--- /dev/null
+++ b/dex/recovery.go
@@ -0,0 +1,484 @@
+// Copyright 2018 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package dex
+
+import (
+	"crypto/ecdsa"
+	"encoding/hex"
+	"fmt"
+	"math/big"
+	"strconv"
+	"strings"
+
+	"github.com/dexon-foundation/dexon/accounts/abi"
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/core/types"
+	"github.com/dexon-foundation/dexon/crypto"
+	"github.com/dexon-foundation/dexon/params"
+	"github.com/dexon-foundation/dexon/rlp"
+	"github.com/onrik/ethrpc"
+)
+
+const numConfirmation = 1
+
+const recoveryABI = `
+[
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      },
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "name": "voted",
+    "outputs": [
+      {
+        "name": "",
+        "type": "bool"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [],
+    "name": "renounceOwnership",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "owner",
+    "outputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "isOwner",
+    "outputs": [
+      {
+        "name": "",
+        "type": "bool"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "depositValue",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      },
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "name": "votes",
+    "outputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "",
+        "type": "address"
+      }
+    ],
+    "name": "withdrawable",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "newOwner",
+        "type": "address"
+      }
+    ],
+    "name": "transferOwnership",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "height",
+        "type": "uint256"
+      },
+      {
+        "indexed": false,
+        "name": "voter",
+        "type": "address"
+      }
+    ],
+    "name": "VotedForRecovery",
+    "type": "event"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "owner",
+        "type": "address"
+      },
+      {
+        "indexed": false,
+        "name": "amount",
+        "type": "uint256"
+      }
+    ],
+    "name": "Withdrawn",
+    "type": "event"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "previousOwner",
+        "type": "address"
+      },
+      {
+        "indexed": true,
+        "name": "newOwner",
+        "type": "address"
+      }
+    ],
+    "name": "OwnershipTransferred",
+    "type": "event"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "DepositValue",
+        "type": "uint256"
+      }
+    ],
+    "name": "setDeposit",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      },
+      {
+        "name": "value",
+        "type": "uint256"
+      }
+    ],
+    "name": "refund",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [],
+    "name": "withdraw",
+    "outputs": [],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      }
+    ],
+    "name": "voteForSkipBlock",
+    "outputs": [],
+    "payable": true,
+    "stateMutability": "payable",
+    "type": "function"
+  },
+  {
+    "constant": false,
+    "inputs": [
+      {
+        "name": "height",
+        "type": "uint256"
+      }
+    ],
+    "name": "numVotes",
+    "outputs": [
+      {
+        "name": "",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "nonpayable",
+    "type": "function"
+  }
+]
+`
+
+var abiObject abi.ABI
+
+func init() {
+	var err error
+	abiObject, err = abi.JSON(strings.NewReader(recoveryABI))
+	if err != nil {
+		panic(err)
+	}
+}
+
+type Recovery struct {
+	gov          *DexconGovernance
+	contract     common.Address
+	confirmation int
+	privateKey   *ecdsa.PrivateKey
+	nodeAddress  common.Address
+	client       *ethrpc.EthRPC
+}
+
+func NewRecovery(config *params.RecoveryConfig, networkRPC string,
+	gov *DexconGovernance, privKey *ecdsa.PrivateKey) *Recovery {
+	client := ethrpc.New(networkRPC)
+	return &Recovery{
+		gov:          gov,
+		contract:     config.Contract,
+		confirmation: config.Confirmation,
+		privateKey:   privKey,
+		nodeAddress:  crypto.PubkeyToAddress(privKey.PublicKey),
+		client:       client,
+	}
+}
+
+func (r *Recovery) genVoteForSkipBlockTx(height uint64) (*types.Transaction, error) {
+	netVersion, err := r.client.NetVersion()
+	if err != nil {
+		return nil, err
+	}
+
+	networkID, err := strconv.Atoi(netVersion)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := abiObject.Pack("depositValue")
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := r.client.EthCall(ethrpc.T{
+		From: r.nodeAddress.String(),
+		To:   r.contract.String(),
+		Data: "0x" + hex.EncodeToString(data),
+	}, "latest")
+	if err != nil {
+		return nil, err
+	}
+
+	resBytes, err := hex.DecodeString(res[2:])
+	if err != nil {
+		return nil, err
+	}
+
+	var depositValue *big.Int
+	err = abiObject.Unpack(&depositValue, "depositValue", resBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err = abiObject.Pack("voteForSkipBlock", new(big.Int).SetUint64(height))
+	if err != nil {
+		return nil, err
+	}
+
+	gasPrice, err := r.client.EthGasPrice()
+	if err != nil {
+		return nil, err
+	}
+
+	nonce, err := r.client.EthGetTransactionCount(r.nodeAddress.String(), "pending")
+	if err != nil {
+		return nil, err
+	}
+
+	// Increase gasPrice to 3 times of suggested gas price to make sure it will
+	// be included in time.
+	useGasPrice := new(big.Int).Mul(&gasPrice, big.NewInt(3))
+
+	tx := types.NewTransaction(
+		uint64(nonce),
+		r.contract,
+		depositValue,
+		uint64(100000),
+		useGasPrice,
+		data)
+
+	signer := types.NewEIP155Signer(big.NewInt(int64(networkID)))
+	return types.SignTx(tx, signer, r.privateKey)
+}
+
+func (r *Recovery) ProposeSkipBlock(height uint64) error {
+	tx, err := r.genVoteForSkipBlockTx(height)
+	if err != nil {
+		return err
+	}
+
+	txData, err := rlp.EncodeToBytes(tx)
+	if err != nil {
+		return err
+	}
+	_, err = r.client.EthSendRawTransaction("0x" + hex.EncodeToString(txData))
+	return err
+}
+
+func (r *Recovery) Votes(height uint64) (uint64, error) {
+	data, err := abiObject.Pack("numVotes", new(big.Int).SetUint64(height))
+	if err != nil {
+		return 0, err
+	}
+
+	bn, err := r.client.EthBlockNumber()
+	if err != nil {
+		return 0, err
+	}
+
+	snapshotHeight := bn - numConfirmation
+
+	res, err := r.client.EthCall(ethrpc.T{
+		From: r.nodeAddress.String(),
+		To:   r.contract.String(),
+		Data: "0x" + hex.EncodeToString(data),
+	}, fmt.Sprintf("0x%x", snapshotHeight))
+	if err != nil {
+		return 0, err
+	}
+
+	resBytes, err := hex.DecodeString(res[2:])
+	if err != nil {
+		return 0, err
+	}
+
+	votes := new(big.Int)
+	err = abiObject.Unpack(&votes, "numVotes", resBytes)
+	if err != nil {
+		return 0, err
+	}
+
+	notarySet, err := r.gov.NotarySetAddresses(r.gov.Round())
+	if err != nil {
+		return 0, err
+	}
+
+	count := uint64(0)
+
+	for i := uint64(0); i < votes.Uint64(); i++ {
+		data, err = abiObject.Pack(
+			"votes", new(big.Int).SetUint64(height), new(big.Int).SetUint64(i))
+		if err != nil {
+			return 0, err
+		}
+
+		res, err = r.client.EthCall(ethrpc.T{
+			From: r.nodeAddress.String(),
+			To:   r.contract.String(),
+			Data: "0x" + hex.EncodeToString(data),
+		}, fmt.Sprintf("0x%x", snapshotHeight))
+		if err != nil {
+			return 0, err
+		}
+
+		resBytes, err := hex.DecodeString(res[2:])
+		if err != nil {
+			return 0, err
+		}
+
+		var addr common.Address
+		err = abiObject.Unpack(&addr, "votes", resBytes)
+		if err != nil {
+			return 0, err
+		}
+
+		if _, ok := notarySet[addr]; ok {
+			count += 1
+		}
+	}
+	return count, nil
+}
diff --git a/dex/recovery_test.go b/dex/recovery_test.go
new file mode 100644
index 000000000..8c039db35
--- /dev/null
+++ b/dex/recovery_test.go
@@ -0,0 +1,43 @@
+// Copyright 2018 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package dex
+
+import (
+	"testing"
+
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/crypto"
+	"github.com/dexon-foundation/dexon/params"
+)
+
+func TestRecoveryVoteTxGeneration(t *testing.T) {
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		t.Fatalf("failed to generate keypair: %v", err)
+	}
+
+	r := NewRecovery(&params.RecoveryConfig{
+		Contract:     common.HexToAddress("f675c0e9bf4b949f50dcec5b224a70f0361d4680"),
+		Timeout:      30,
+		Confirmation: 1,
+	}, "https://rinkeby.infura.io", nil, key)
+	_, err = r.genVoteForSkipBlockTx(0)
+	if err != nil {
+		t.Fatalf("failed to generate voteForSkipBlock tx: %v", err)
+	}
+}
diff --git a/params/config.go b/params/config.go
index 8cf986f55..4eefc8f08 100644
--- a/params/config.go
+++ b/params/config.go
@@ -75,6 +75,11 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
 		},
+		Recovery: &RecoveryConfig{
+			Contract:     common.HexToAddress("0xcb4bb8ae26b2ebe5a1e2e8d5236020f33ffb2294"),
+			Timeout:      120,
+			Confirmation: 5,
+		},
 	}
 
 	// MainnetTrustedCheckpoint contains the light client trusted checkpoint for the main network.
@@ -121,6 +126,11 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
 		},
+		Recovery: &RecoveryConfig{
+			Contract:     common.HexToAddress("0x4ebe3d13ab18b30d815711b7a33ef1226777b66d"),
+			Timeout:      120,
+			Confirmation: 5,
+		},
 	}
 
 	// TaipeiChainConfig contains the chain parameters to run a node on the Taipei test network.
@@ -158,6 +168,11 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
 		},
+		Recovery: &RecoveryConfig{
+			Contract:     common.HexToAddress("0xac86ab80ab27007801f36f6622fbe0a9432291a2"),
+			Timeout:      120,
+			Confirmation: 1,
+		},
 	}
 
 	// TestnetTrustedCheckpoint contains the light client trusted checkpoint for the Ropsten test network.
@@ -203,6 +218,11 @@ var (
 				new(big.Int).Mul(big.NewInt(1e18), big.NewInt(1e5)),
 			},
 		},
+		Recovery: &RecoveryConfig{
+			Contract:     common.HexToAddress("0x3828134ba7a0629fd52067b80fe696f400eb83dc"),
+			Timeout:      120,
+			Confirmation: 1,
+		},
 	}
 
 	// AllEthashProtocolChanges contains every protocol change (EIPs) introduced
@@ -210,18 +230,18 @@ var (
 	//
 	// This configuration is intentionally not using keyed fields to force anyone
 	// adding flags to the config to also have to set these fields.
-	AllEthashProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, nil}
+	AllEthashProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, nil, nil}
 
 	// AllCliqueProtocolChanges contains every protocol change (EIPs) introduced
 	// and accepted by the Ethereum core developers into the Clique consensus.
 	//
 	// This configuration is intentionally not using keyed fields to force anyone
 	// adding flags to the config to also have to set these fields.
-	AllCliqueProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, &CliqueConfig{Period: 0, Epoch: 30000}, nil}
+	AllCliqueProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, &CliqueConfig{Period: 0, Epoch: 30000}, nil, nil}
 
-	AllDexconProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, nil, new(DexconConfig)}
+	AllDexconProtocolChanges = &ChainConfig{big.NewInt(1337), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, nil, nil, new(DexconConfig), new(RecoveryConfig)}
 
-	TestChainConfig = &ChainConfig{big.NewInt(1), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, nil}
+	TestChainConfig = &ChainConfig{big.NewInt(1), 0, big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil, nil, nil}
 	TestRules       = TestChainConfig.Rules(new(big.Int))
 
 	// Ethereum MainnetChainConfig is the chain parameters to run a node on the main network.
@@ -299,6 +319,9 @@ type ChainConfig struct {
 	Ethash *EthashConfig `json:"ethash,omitempty"`
 	Clique *CliqueConfig `json:"clique,omitempty"`
 	Dexcon *DexconConfig `json:"dexcon,omitempty"`
+
+	// Dexcon Recovery
+	Recovery *RecoveryConfig `json:"recovery,omitempty"`
 }
 
 // EthashConfig is the consensus engine configs for proof-of-work based sealing.
@@ -372,6 +395,12 @@ func (d *DexconConfig) String() string {
 	)
 }
 
+type RecoveryConfig struct {
+	Contract     common.Address `json:"contract"`
+	Timeout      int            `json:"timeout"`
+	Confirmation int            `json:"confirmation"`
+}
+
 // String implements the fmt.Stringer interface.
 func (c *ChainConfig) String() string {
 	var engine interface{}
diff --git a/params/gen_dexcon_config.go b/params/gen_dexcon_config.go
index 1afe11f56..38753916a 100644
--- a/params/gen_dexcon_config.go
+++ b/params/gen_dexcon_config.go
@@ -22,6 +22,7 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 		MiningVelocity    float32                 `json:"miningVelocity"`
 		NextHalvingSupply *math.HexOrDecimal256   `json:"nextHalvingSupply"`
 		LastHalvedAmount  *math.HexOrDecimal256   `json:"lastHalvedAmount"`
+		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 		BlockGasLimit     uint64                  `json:"blockGasLimit"`
 		LambdaBA          uint64                  `json:"lambdaBA"`
 		LambdaDKG         uint64                  `json:"lambdaDKG"`
@@ -30,7 +31,6 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 		RoundLength       uint64                  `json:"roundLength"`
 		MinBlockInterval  uint64                  `json:"minBlockInterval"`
 		FineValues        []*math.HexOrDecimal256 `json:"fineValues"`
-		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 	}
 	var enc DexconConfig
 	enc.GenesisCRSText = d.GenesisCRSText
@@ -40,6 +40,7 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 	enc.MiningVelocity = d.MiningVelocity
 	enc.NextHalvingSupply = (*math.HexOrDecimal256)(d.NextHalvingSupply)
 	enc.LastHalvedAmount = (*math.HexOrDecimal256)(d.LastHalvedAmount)
+	enc.MinGasPrice = (*math.HexOrDecimal256)(d.MinGasPrice)
 	enc.BlockGasLimit = d.BlockGasLimit
 	enc.LambdaBA = d.LambdaBA
 	enc.LambdaDKG = d.LambdaDKG
@@ -53,7 +54,6 @@ func (d DexconConfig) MarshalJSON() ([]byte, error) {
 			enc.FineValues[k] = (*math.HexOrDecimal256)(v)
 		}
 	}
-	enc.MinGasPrice = (*math.HexOrDecimal256)(d.MinGasPrice)
 	return json.Marshal(&enc)
 }
 
@@ -67,6 +67,7 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 		MiningVelocity    *float32                `json:"miningVelocity"`
 		NextHalvingSupply *math.HexOrDecimal256   `json:"nextHalvingSupply"`
 		LastHalvedAmount  *math.HexOrDecimal256   `json:"lastHalvedAmount"`
+		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 		BlockGasLimit     *uint64                 `json:"blockGasLimit"`
 		LambdaBA          *uint64                 `json:"lambdaBA"`
 		LambdaDKG         *uint64                 `json:"lambdaDKG"`
@@ -75,7 +76,6 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 		RoundLength       *uint64                 `json:"roundLength"`
 		MinBlockInterval  *uint64                 `json:"minBlockInterval"`
 		FineValues        []*math.HexOrDecimal256 `json:"fineValues"`
-		MinGasPrice       *math.HexOrDecimal256   `json:"minGasPrice"`
 	}
 	var dec DexconConfig
 	if err := json.Unmarshal(input, &dec); err != nil {
@@ -102,6 +102,9 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 	if dec.LastHalvedAmount != nil {
 		d.LastHalvedAmount = (*big.Int)(dec.LastHalvedAmount)
 	}
+	if dec.MinGasPrice != nil {
+		d.MinGasPrice = (*big.Int)(dec.MinGasPrice)
+	}
 	if dec.BlockGasLimit != nil {
 		d.BlockGasLimit = *dec.BlockGasLimit
 	}
@@ -129,8 +132,5 @@ func (d *DexconConfig) UnmarshalJSON(input []byte) error {
 			d.FineValues[k] = (*big.Int)(v)
 		}
 	}
-	if dec.MinGasPrice != nil {
-		d.MinGasPrice = (*big.Int)(dec.MinGasPrice)
-	}
 	return nil
 }
diff --git a/test/genesis.json b/test/genesis.json
index fc6cd7fe4..8be5a844d 100644
--- a/test/genesis.json
+++ b/test/genesis.json
@@ -19,6 +19,7 @@
       "miningVelocity": 0.1875,
       "nextHalvingSupply": "0x813f3978f89409844000000",
       "lastHalvedAmount": "0x4d8c55aefb8c05b5c000000",
+      "minGasPrice": "0x3b9aca00",
       "blockGasLimit": 40000000,
       "lambdaBA": 250,
       "lambdaDKG": 1500,
@@ -30,8 +31,12 @@
         "0x21e19e0c9bab2400000",
         "0x21e19e0c9bab2400000",
         "0x152d02c7e14af6800000"
-      ],
-      "minGasPrice": "0x3b9aca00"
+      ]
+    },
+    "recovery": {
+      "contract": "0xf675c0e9bf4b949f50dcec5b224a70f0361d4680",
+      "timeout": 30,
+      "confirmation": 1
     }
   },
   "nonce": "0x42",
diff --git a/test/run_test.sh b/test/run_test.sh
index 48934ab7c..b6db1ba09 100755
--- a/test/run_test.sh
+++ b/test/run_test.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-NETWORK="--bootnodes enode://0478aa13c91aa0db8e93b668313b7eb0532fbdb24f64772375373b14dbe326c238ad09ab4469f6442c9a9753f1275aeec2e531912c14a958ed1feb4ae7e227ef@127.0.0.1:30301"
+BOOTNODE_FLAGS="--bootnodes enode://0478aa13c91aa0db8e93b668313b7eb0532fbdb24f64772375373b14dbe326c238ad09ab4469f6442c9a9753f1275aeec2e531912c14a958ed1feb4ae7e227ef@127.0.0.1:30301"
 GENESIS="genesis.json"
 
 GDEX="../build/bin/gdex"
@@ -42,10 +42,12 @@ __FILE__
 
 # A standalone RPC server for accepting RPC requests.
 datadir=$PWD/Dexon.rpc
-rm -rf $datadir
-$GDEX --datadir=$datadir init ${GENESIS}
+if [ "$1" != "--continue" ]; then
+  rm -rf $datadir
+  $GDEX --datadir=$datadir init ${GENESIS}
+fi
 $GDEX \
-  ${NETWORK} \
+  ${BOOTNODE_FLAGS} \
   --verbosity=3 \
   --gcmode=archive \
   --datadir=$datadir --nodekey=keystore/rpc.key \
@@ -61,15 +63,19 @@ NUM_NODES=$(cat ${GENESIS} | grep 'DEXON Test Node' | wc -l)
 # Nodes
 for i in $(seq 0 $(($NUM_NODES - 1))); do
   datadir=$PWD/Dexon.$i
-  rm -rf $datadir
-  $GDEX --datadir=$datadir init ${GENESIS}
+
+  if [ "$1" != "--continue" ]; then
+    rm -rf $datadir
+    $GDEX --datadir=$datadir init ${GENESIS}
+  fi
   $GDEX \
-    ${NETWORK} \
+    ${BOOTNODE_FLAGS} \
     --bp \
     --verbosity=4 \
     --gcmode=archive \
     --datadir=$datadir --nodekey=keystore/test$i.key \
     --port=$((30305 + $i)) \
+    --recovery.network-rpc="https://rinkeby.infura.io" \
     --rpc --rpcapi=eth,net,web3,debug \
     --rpcaddr=0.0.0.0 --rpcport=$((8547 + $i * 2)) \
     --ws --wsapi=eth,net,web3,debug \
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/agreement-mgr.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/agreement-mgr.go
index 7b5effba8..0e39fa52a 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/agreement-mgr.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/agreement-mgr.go
@@ -90,8 +90,6 @@ func newAgreementMgrConfig(prev agreementMgrConfig, config *types.Config,
 
 type baRoundSetting struct {
 	notarySet map[types.NodeID]struct{}
-	agr       *agreement
-	recv      *consensusBAReceiver
 	ticker    Ticker
 	crs       common.Hash
 }
@@ -111,6 +109,7 @@ type agreementMgr struct {
 	initRound         uint64
 	configs           []agreementMgrConfig
 	baModule          *agreement
+	recv              *consensusBAReceiver
 	processedBAResult map[types.Position]struct{}
 	voteFilter        *utils.VoteFilter
 	waitGroup         sync.WaitGroup
@@ -136,15 +135,17 @@ func newAgreementMgr(con *Consensus, initRound uint64,
 		configs:           []agreementMgrConfig{initConfig},
 		voteFilter:        utils.NewVoteFilter(),
 	}
-	recv := &consensusBAReceiver{
-		consensus:     con,
-		restartNotary: make(chan types.Position, 1),
-		roundValue:    &atomic.Value{},
+	mgr.recv = &consensusBAReceiver{
+		consensus:               con,
+		restartNotary:           make(chan types.Position, 1),
+		roundValue:              &atomic.Value{},
+		changeNotaryHeightValue: &atomic.Value{},
 	}
-	recv.roundValue.Store(uint64(0))
+	mgr.recv.roundValue.Store(uint64(0))
+	mgr.recv.changeNotaryHeightValue.Store(uint64(0))
 	agr := newAgreement(
 		mgr.ID,
-		recv,
+		mgr.recv,
 		newLeaderSelector(genValidLeader(mgr), mgr.logger),
 		mgr.signer,
 		mgr.logger)
@@ -156,7 +157,7 @@ func newAgreementMgr(con *Consensus, initRound uint64,
 	agr.notarySet = nodes.GetSubSet(
 		int(initConfig.notarySetSize), types.NewNotarySetTarget(initConfig.crs))
 	// Hacky way to make agreement module self contained.
-	recv.agreementModule = agr
+	mgr.recv.agreementModule = agr
 	mgr.baModule = agr
 	return
 }
@@ -188,15 +189,43 @@ func (mgr *agreementMgr) config(round uint64) *agreementMgrConfig {
 	return &mgr.configs[roundIndex]
 }
 
-func (mgr *agreementMgr) appendConfig(
-	round uint64, config *types.Config, crs common.Hash) (err error) {
+func (mgr *agreementMgr) notifyRoundEvents(evts []utils.RoundEventParam) error {
 	mgr.lock.Lock()
 	defer mgr.lock.Unlock()
-	if round != uint64(len(mgr.configs))+mgr.initRound {
-		return ErrRoundNotIncreasing
+	apply := func(e utils.RoundEventParam) error {
+		if len(mgr.configs) > 0 {
+			lastCfg := mgr.configs[len(mgr.configs)-1]
+			if e.BeginHeight != lastCfg.RoundEndHeight() {
+				return ErrInvalidBlockHeight
+			}
+			if lastCfg.RoundID() == e.Round {
+				mgr.configs[len(mgr.configs)-1].ExtendLength()
+				// It's not an atomic operation to update an atomic value based
+				// on another. However, it's the best way so far to extend
+				// length of round without refactoring.
+				if mgr.recv.round() == e.Round {
+					mgr.recv.changeNotaryHeightValue.Store(
+						mgr.configs[len(mgr.configs)-1].RoundEndHeight())
+				}
+			} else if lastCfg.RoundID()+1 == e.Round {
+				mgr.configs = append(mgr.configs, newAgreementMgrConfig(
+					lastCfg, e.Config, e.CRS))
+			} else {
+				return ErrInvalidRoundID
+			}
+		} else {
+			c := agreementMgrConfig{}
+			c.from(e.Round, e.Config, e.CRS)
+			c.SetRoundBeginHeight(e.BeginHeight)
+			mgr.configs = append(mgr.configs, c)
+		}
+		return nil
+	}
+	for _, e := range evts {
+		if err := apply(e); err != nil {
+			return err
+		}
 	}
-	mgr.configs = append(mgr.configs, newAgreementMgrConfig(
-		mgr.configs[len(mgr.configs)-1], config, crs))
 	return nil
 }
 
@@ -252,7 +281,7 @@ func (mgr *agreementMgr) processAgreementResult(
 		}
 	} else if result.Position.Newer(aID) {
 		mgr.logger.Info("Fast syncing BA", "position", result.Position)
-		nodes, err := mgr.cache.GetNodeSet(result.Position.Round)
+		nIDs, err := mgr.cache.GetNotarySet(result.Position.Round)
 		if err != nil {
 			return err
 		}
@@ -261,10 +290,6 @@ func (mgr *agreementMgr) processAgreementResult(
 		mgr.network.PullBlocks(common.Hashes{result.BlockHash})
 		mgr.logger.Debug("Calling Governance.CRS", "round", result.Position.Round)
 		crs := utils.GetCRSWithPanic(mgr.gov, result.Position.Round, mgr.logger)
-		nIDs := nodes.GetSubSet(
-			int(utils.GetConfigWithPanic(
-				mgr.gov, result.Position.Round, mgr.logger).NotarySetSize),
-			types.NewNotarySetTarget(crs))
 		for key := range result.Votes {
 			if err := mgr.baModule.processVote(&result.Votes[key]); err != nil {
 				return err
@@ -296,10 +321,7 @@ func (mgr *agreementMgr) runBA(initRound uint64) {
 		currentRound uint64
 		nextRound    = initRound
 		curConfig    = mgr.config(initRound)
-		setting      = baRoundSetting{
-			agr:  mgr.baModule,
-			recv: mgr.baModule.data.recv.(*consensusBAReceiver),
-		}
+		setting      = baRoundSetting{}
 		tickDuration time.Duration
 	)
 
@@ -353,12 +375,12 @@ Loop:
 			break Loop
 		default:
 		}
-		setting.recv.isNotary = checkRound()
+		mgr.recv.isNotary = checkRound()
 		// Run BA for this round.
-		setting.recv.roundValue.Store(currentRound)
-		setting.recv.changeNotaryHeight = curConfig.RoundEndHeight()
-		setting.recv.restartNotary <- types.Position{
-			Round:  setting.recv.round(),
+		mgr.recv.roundValue.Store(currentRound)
+		mgr.recv.changeNotaryHeightValue.Store(curConfig.RoundEndHeight())
+		mgr.recv.restartNotary <- types.Position{
+			Round:  mgr.recv.round(),
 			Height: math.MaxUint64,
 		}
 		mgr.voteFilter = utils.NewVoteFilter()
@@ -373,8 +395,8 @@ Loop:
 
 func (mgr *agreementMgr) baRoutineForOneRound(
 	setting *baRoundSetting) (err error) {
-	agr := setting.agr
-	recv := setting.recv
+	agr := mgr.baModule
+	recv := mgr.recv
 	oldPos := agr.agreementID()
 	restart := func(restartPos types.Position) (breakLoop bool, err error) {
 		if !isStop(restartPos) {
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/blockchain.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/blockchain.go
index 19a580b4f..c5a22b628 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/blockchain.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/blockchain.go
@@ -41,7 +41,6 @@ var (
 	ErrNotFollowTipPosition           = errors.New("not follow tip position")
 	ErrDuplicatedPendingBlock         = errors.New("duplicated pending block")
 	ErrRetrySanityCheckLater          = errors.New("retry sanity check later")
-	ErrRoundNotIncreasing             = errors.New("round not increasing")
 	ErrRoundNotSwitch                 = errors.New("round not switch")
 	ErrIncorrectBlockRandomnessResult = errors.New(
 		"incorrect block randomness result")
@@ -142,19 +141,8 @@ type blockChain struct {
 }
 
 func newBlockChain(nID types.NodeID, dMoment time.Time, initBlock *types.Block,
-	initConfig blockChainConfig, app Application, vGetter tsigVerifierGetter,
-	signer *utils.Signer, logger common.Logger) *blockChain {
-	if initBlock != nil {
-		if initConfig.RoundID() != initBlock.Position.Round {
-			panic(fmt.Errorf("incompatible config/block %s %d",
-				initBlock, initConfig.RoundID()))
-		}
-	} else {
-		if initConfig.RoundID() != 0 {
-			panic(fmt.Errorf("genesis config should from round 0 %d",
-				initConfig.RoundID()))
-		}
-	}
+	app Application, vGetter tsigVerifierGetter, signer *utils.Signer,
+	logger common.Logger) *blockChain {
 	return &blockChain{
 		ID:            nID,
 		lastConfirmed: initBlock,
@@ -163,23 +151,58 @@ func newBlockChain(nID types.NodeID, dMoment time.Time, initBlock *types.Block,
 		vGetter:       vGetter,
 		app:           app,
 		logger:        logger,
-		configs:       []blockChainConfig{initConfig},
 		dMoment:       dMoment,
 		pendingRandomnesses: make(
 			map[types.Position]*types.BlockRandomnessResult),
 	}
 }
 
-func (bc *blockChain) appendConfig(round uint64, config *types.Config) error {
-	expectedRound := uint64(len(bc.configs))
-	if bc.lastConfirmed != nil {
-		expectedRound += bc.lastConfirmed.Position.Round
+func (bc *blockChain) notifyRoundEvents(evts []utils.RoundEventParam) error {
+	bc.lock.Lock()
+	defer bc.lock.Unlock()
+	apply := func(e utils.RoundEventParam) error {
+		if len(bc.configs) > 0 {
+			lastCfg := bc.configs[len(bc.configs)-1]
+			if e.BeginHeight != lastCfg.RoundEndHeight() {
+				return ErrInvalidBlockHeight
+			}
+			if lastCfg.RoundID() == e.Round {
+				bc.configs[len(bc.configs)-1].ExtendLength()
+			} else if lastCfg.RoundID()+1 == e.Round {
+				bc.configs = append(bc.configs, newBlockChainConfig(
+					lastCfg, e.Config))
+			} else {
+				return ErrInvalidRoundID
+			}
+		} else {
+			c := blockChainConfig{}
+			c.fromConfig(e.Round, e.Config)
+			c.SetRoundBeginHeight(e.BeginHeight)
+			if bc.lastConfirmed == nil {
+				if c.RoundID() != 0 {
+					panic(fmt.Errorf("genesis config should from round 0 %d",
+						c.RoundID()))
+				}
+			} else {
+				if c.RoundID() != bc.lastConfirmed.Position.Round {
+					panic(fmt.Errorf("incompatible config/block %s %d",
+						bc.lastConfirmed, c.RoundID()))
+				}
+				if !c.Contains(bc.lastConfirmed.Position.Height) {
+					panic(fmt.Errorf(
+						"unmatched round-event with block %s %d %d %d",
+						bc.lastConfirmed, e.Round, e.Reset, e.BeginHeight))
+				}
+			}
+			bc.configs = append(bc.configs, c)
+		}
+		return nil
 	}
-	if round != expectedRound {
-		return ErrRoundNotIncreasing
+	for _, e := range evts {
+		if err := apply(e); err != nil {
+			return err
+		}
 	}
-	bc.configs = append(bc.configs, newBlockChainConfig(
-		bc.configs[len(bc.configs)-1], config))
 	return nil
 }
 
@@ -558,8 +581,11 @@ func (bc *blockChain) prepareBlock(position types.Position,
 		}
 		if tipConfig.IsLastBlock(tip) {
 			if tip.Position.Round+1 != position.Round {
-				b, err = nil, ErrRoundNotSwitch
-				return
+				if !empty {
+					b, err = nil, ErrRoundNotSwitch
+					return
+				}
+				b.Position.Round = tip.Position.Round + 1
 			}
 		} else {
 			if tip.Position.Round != position.Round {
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus.go
index 4201cbcc2..8529e4031 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus.go
@@ -56,18 +56,22 @@ var (
 // consensusBAReceiver implements agreementReceiver.
 type consensusBAReceiver struct {
 	// TODO(mission): consensus would be replaced by blockChain and network.
-	consensus          *Consensus
-	agreementModule    *agreement
-	changeNotaryHeight uint64
-	roundValue         *atomic.Value
-	isNotary           bool
-	restartNotary      chan types.Position
+	consensus               *Consensus
+	agreementModule         *agreement
+	changeNotaryHeightValue *atomic.Value
+	roundValue              *atomic.Value
+	isNotary                bool
+	restartNotary           chan types.Position
 }
 
 func (recv *consensusBAReceiver) round() uint64 {
 	return recv.roundValue.Load().(uint64)
 }
 
+func (recv *consensusBAReceiver) changeNotaryHeight() uint64 {
+	return recv.changeNotaryHeightValue.Load().(uint64)
+}
+
 func (recv *consensusBAReceiver) ProposeVote(vote *types.Vote) {
 	if !recv.isNotary {
 		return
@@ -247,16 +251,17 @@ CleanChannelLoop:
 		}
 	}
 	newPos := block.Position
-	if block.Position.Height+1 == recv.changeNotaryHeight {
+	if block.Position.Height+1 == recv.changeNotaryHeight() {
 		newPos.Round++
 		recv.roundValue.Store(newPos.Round)
 	}
 	currentRound := recv.round()
-	if block.Position.Height > recv.changeNotaryHeight &&
+	changeNotaryHeight := recv.changeNotaryHeight()
+	if block.Position.Height > changeNotaryHeight &&
 		block.Position.Round <= currentRound {
 		panic(fmt.Errorf(
 			"round not switch when confirmig: %s, %d, should switch at %d",
-			block, currentRound, recv.changeNotaryHeight))
+			block, currentRound, changeNotaryHeight))
 	}
 	recv.restartNotary <- newPos
 }
@@ -396,11 +401,11 @@ type Consensus struct {
 	bcModule                 *blockChain
 	dMoment                  time.Time
 	nodeSetCache             *utils.NodeSetCache
-	roundForNewConfig        uint64
 	lock                     sync.RWMutex
 	ctx                      context.Context
 	ctxCancel                context.CancelFunc
 	event                    *common.Event
+	roundEvent               *utils.RoundEvent
 	logger                   common.Logger
 	resetRandomnessTicker    chan struct{}
 	resetDeliveryGuardTicker chan struct{}
@@ -453,6 +458,7 @@ func NewConsensusForSimulation(
 func NewConsensusFromSyncer(
 	initBlock *types.Block,
 	initRoundBeginHeight uint64,
+	startWithEmpty bool,
 	dMoment time.Time,
 	app Application,
 	gov Governance,
@@ -495,6 +501,23 @@ func NewConsensusFromSyncer(
 			continue
 		}
 	}
+	if startWithEmpty {
+		pos := initBlock.Position
+		pos.Height++
+		block, err := con.bcModule.addEmptyBlock(pos)
+		if err != nil {
+			panic(err)
+		}
+		con.processBlockChan <- block
+		if pos.Round >= DKGDelayRound {
+			rand := &types.AgreementResult{
+				BlockHash:    block.Hash,
+				Position:     block.Position,
+				IsEmptyBlock: true,
+			}
+			go con.prepareRandomnessResult(rand)
+		}
+	}
 	return con, nil
 }
 
@@ -522,8 +545,10 @@ func newConsensusForRound(
 	}
 	// Get configuration for bootstrap round.
 	initRound := uint64(0)
+	initBlockHeight := uint64(0)
 	if initBlock != nil {
 		initRound = initBlock.Position.Round
+		initBlockHeight = initBlock.Position.Height
 	}
 	initConfig := utils.GetConfigWithPanic(gov, initRound, logger)
 	initCRS := utils.GetCRSWithPanic(gov, initRound, logger)
@@ -548,10 +573,7 @@ func newConsensusForRound(
 	if usingNonBlocking {
 		appModule = newNonBlocking(app, debugApp)
 	}
-	bcConfig := blockChainConfig{}
-	bcConfig.fromConfig(initRound, initConfig)
-	bcConfig.SetRoundBeginHeight(initRoundBeginHeight)
-	bcModule := newBlockChain(ID, dMoment, initBlock, bcConfig, appModule,
+	bcModule := newBlockChain(ID, dMoment, initBlock, appModule,
 		NewTSigVerifierCache(gov, 7), signer, logger)
 	// Construct Consensus instance.
 	con := &Consensus{
@@ -576,6 +598,10 @@ func newConsensusForRound(
 		processBlockChan:         make(chan *types.Block, 1024),
 	}
 	con.ctx, con.ctxCancel = context.WithCancel(context.Background())
+	if con.roundEvent, err = utils.NewRoundEvent(con.ctx, gov, logger, initRound,
+		initRoundBeginHeight, initBlockHeight, ConfigRoundShift); err != nil {
+		panic(err)
+	}
 	baConfig := agreementMgrConfig{}
 	baConfig.from(initRound, initConfig, initCRS)
 	baConfig.SetRoundBeginHeight(initRoundBeginHeight)
@@ -595,26 +621,139 @@ func newConsensusForRound(
 //  - the last finalized block
 func (con *Consensus) prepare(
 	initRoundBeginHeight uint64, initBlock *types.Block) (err error) {
+	// Trigger the round validation method for the next round of the first
+	// round.
 	// The block past from full node should be delivered already or known by
 	// full node. We don't have to notify it.
 	initRound := uint64(0)
 	if initBlock != nil {
 		initRound = initBlock.Position.Round
 	}
-	// Setup blockChain module.
-	con.roundForNewConfig = initRound + 1
-	initConfig := utils.GetConfigWithPanic(con.gov, initRound, con.logger)
-	initPlusOneCfg := utils.GetConfigWithPanic(con.gov, initRound+1, con.logger)
-	if err = con.bcModule.appendConfig(initRound+1, initPlusOneCfg); err != nil {
-		return
-	}
 	if initRound == 0 {
 		if DKGDelayRound == 0 {
 			panic("not implemented yet")
 		}
 	}
-	// Register events.
-	con.initialRound(initRoundBeginHeight, initRound, initConfig)
+	// Register round event handler to update BA and BC modules.
+	con.roundEvent.Register(func(evts []utils.RoundEventParam) {
+		// Always updates newer configs to the later modules first in the flow.
+		if err := con.bcModule.notifyRoundEvents(evts); err != nil {
+			panic(err)
+		}
+		// The init config is provided to baModule when construction.
+		if evts[len(evts)-1].BeginHeight != initRoundBeginHeight {
+			if err := con.baMgr.notifyRoundEvents(evts); err != nil {
+				panic(err)
+			}
+		}
+	})
+	// Register round event handler to propose new CRS.
+	con.roundEvent.Register(func(evts []utils.RoundEventParam) {
+		// We don't have to propose new CRS during DKG reset, the reset of DKG
+		// would be done by the DKG set in previous round.
+		e := evts[len(evts)-1]
+		if e.Reset != 0 || e.Round < DKGDelayRound {
+			return
+		}
+		if curDkgSet, err := con.nodeSetCache.GetDKGSet(e.Round); err != nil {
+			con.logger.Error("Error getting DKG set when proposing CRS",
+				"round", e.Round,
+				"error", err)
+		} else {
+			if _, exist := curDkgSet[con.ID]; !exist {
+				return
+			}
+			con.event.RegisterHeight(e.NextCRSProposingHeight(), func(uint64) {
+				con.logger.Debug(
+					"Calling Governance.CRS to check if already proposed",
+					"round", e.Round+1)
+				if (con.gov.CRS(e.Round+1) != common.Hash{}) {
+					con.logger.Debug("CRS already proposed", "round", e.Round+1)
+					return
+				}
+				con.runCRS(e.Round, e.CRS)
+			})
+		}
+	})
+	// Touch nodeSetCache for next round.
+	con.roundEvent.Register(func(evts []utils.RoundEventParam) {
+		e := evts[len(evts)-1]
+		if e.Reset != 0 {
+			return
+		}
+		con.event.RegisterHeight(e.NextTouchNodeSetCacheHeight(), func(uint64) {
+			if err := con.nodeSetCache.Touch(e.Round + 1); err != nil {
+				con.logger.Warn("Failed to update nodeSetCache",
+					"round", e.Round+1,
+					"error", err)
+			}
+		})
+	})
+	// checkCRS is a generator of checker to check if CRS for that round is
+	// ready or not.
+	checkCRS := func(round uint64) func() bool {
+		return func() bool {
+			nextCRS := con.gov.CRS(round)
+			if (nextCRS != common.Hash{}) {
+				return true
+			}
+			con.logger.Debug("CRS is not ready yet. Try again later...",
+				"nodeID", con.ID,
+				"round", round)
+			return false
+		}
+	}
+	// Trigger round validation method for next period.
+	con.roundEvent.Register(func(evts []utils.RoundEventParam) {
+		e := evts[len(evts)-1]
+		// Register a routine to trigger round events.
+		con.event.RegisterHeight(e.NextRoundValidationHeight(), func(
+			blockHeight uint64) {
+			con.roundEvent.ValidateNextRound(blockHeight)
+		})
+		// Register a routine to register next DKG.
+		con.event.RegisterHeight(e.NextDKGRegisterHeight(), func(uint64) {
+			nextRound := e.Round + 1
+			if nextRound < DKGDelayRound {
+				con.logger.Info("Skip runDKG for round", "round", nextRound)
+				return
+			}
+			// Normally, gov.CRS would return non-nil. Use this for in case of
+			// unexpected network fluctuation and ensure the robustness.
+			if !checkWithCancel(
+				con.ctx, 500*time.Millisecond, checkCRS(nextRound)) {
+				con.logger.Debug("unable to prepare CRS for DKG set",
+					"round", nextRound)
+				return
+			}
+			nextDkgSet, err := con.nodeSetCache.GetDKGSet(nextRound)
+			if err != nil {
+				con.logger.Error("Error getting DKG set for next round",
+					"round", nextRound,
+					"error", err)
+				return
+			}
+			if _, exist := nextDkgSet[con.ID]; !exist {
+				con.logger.Info("Not selected as DKG set", "round", nextRound)
+				return
+			}
+			con.logger.Info("Selected as DKG set", "round", nextRound)
+			nextConfig := utils.GetConfigWithPanic(con.gov, nextRound,
+				con.logger)
+			con.cfgModule.registerDKG(nextRound, utils.GetDKGThreshold(
+				nextConfig))
+			con.event.RegisterHeight(e.NextDKGPreparationHeight(),
+				func(uint64) {
+					func() {
+						con.dkgReady.L.Lock()
+						defer con.dkgReady.L.Unlock()
+						con.dkgRunning = 0
+					}()
+					con.runDKG(nextRound, nextConfig)
+				})
+		})
+	})
+	con.roundEvent.TriggerInitEvent()
 	return
 }
 
@@ -686,27 +825,9 @@ func (con *Consensus) runDKG(round uint64, config *types.Config) {
 	}()
 }
 
-func (con *Consensus) runCRS(round uint64) {
-	for {
-		con.logger.Debug("Calling Governance.CRS to check if already proposed",
-			"round", round+1)
-		if (con.gov.CRS(round+1) != common.Hash{}) {
-			con.logger.Debug("CRS already proposed", "round", round+1)
-			return
-		}
-		con.logger.Debug("Calling Governance.IsDKGFinal to check if ready to run CRS",
-			"round", round)
-		if con.cfgModule.isDKGFinal(round) {
-			break
-		}
-		con.logger.Debug("DKG is not ready for running CRS. Retry later...",
-			"round", round)
-		time.Sleep(500 * time.Millisecond)
-	}
+func (con *Consensus) runCRS(round uint64, hash common.Hash) {
 	// Start running next round CRS.
-	con.logger.Debug("Calling Governance.CRS", "round", round)
-	psig, err := con.cfgModule.preparePartialSignature(
-		round, utils.GetCRSWithPanic(con.gov, round, con.logger))
+	psig, err := con.cfgModule.preparePartialSignature(round, hash)
 	if err != nil {
 		con.logger.Error("Failed to prepare partial signature", "error", err)
 	} else if err = con.signer.SignDKGPartialSignature(psig); err != nil {
@@ -733,136 +854,16 @@ func (con *Consensus) runCRS(round uint64) {
 	}
 }
 
-func (con *Consensus) initialRound(
-	startHeight uint64, round uint64, config *types.Config) {
-	select {
-	case <-con.ctx.Done():
-		return
-	default:
-	}
-	if round >= DKGDelayRound {
-		curDkgSet, err := con.nodeSetCache.GetDKGSet(round)
-		if err != nil {
-			con.logger.Error("Error getting DKG set", "round", round, "error", err)
-			curDkgSet = make(map[types.NodeID]struct{})
-		}
-		// Initiate CRS routine.
-		if _, exist := curDkgSet[con.ID]; exist {
-			con.event.RegisterHeight(
-				startHeight+config.RoundLength/2,
-				func(uint64) {
-					go func() {
-						con.runCRS(round)
-					}()
-				})
-		}
-	}
-	// checkCRS is a generator of checker to check if CRS for that round is
-	// ready or not.
-	checkCRS := func(round uint64) func() bool {
-		return func() bool {
-			nextCRS := con.gov.CRS(round)
-			if (nextCRS != common.Hash{}) {
-				return true
-			}
-			con.logger.Debug("CRS is not ready yet. Try again later...",
-				"nodeID", con.ID,
-				"round", round)
-			return false
-		}
-	}
-	// Initiate BA modules.
-	con.event.RegisterHeight(startHeight+config.RoundLength/2, func(uint64) {
-		go func(nextRound uint64) {
-			if !checkWithCancel(
-				con.ctx, 500*time.Millisecond, checkCRS(nextRound)) {
-				con.logger.Debug("unable to prepare CRS for baMgr",
-					"round", nextRound)
-				return
-			}
-			// Notify BA for new round.
-			nextConfig := utils.GetConfigWithPanic(
-				con.gov, nextRound, con.logger)
-			nextCRS := utils.GetCRSWithPanic(
-				con.gov, nextRound, con.logger)
-			con.logger.Info("appendConfig for baMgr", "round", nextRound)
-			if err := con.baMgr.appendConfig(
-				nextRound, nextConfig, nextCRS); err != nil {
-				panic(err)
-			}
-		}(round + 1)
-	})
-	// Initiate DKG for this round.
-	con.event.RegisterHeight(startHeight+config.RoundLength/2, func(uint64) {
-		go func(nextRound uint64) {
-			if nextRound < DKGDelayRound {
-				con.logger.Info("Skip runDKG for round", "round", nextRound)
-				return
-			}
-			// Normally, gov.CRS would return non-nil. Use this for in case of
-			// unexpected network fluctuation and ensure the robustness.
-			if !checkWithCancel(
-				con.ctx, 500*time.Millisecond, checkCRS(nextRound)) {
-				con.logger.Debug("unable to prepare CRS for DKG set",
-					"round", nextRound)
-				return
-			}
-			nextDkgSet, err := con.nodeSetCache.GetDKGSet(nextRound)
-			if err != nil {
-				con.logger.Error("Error getting DKG set",
-					"round", nextRound,
-					"error", err)
-				return
-			}
-			if _, exist := nextDkgSet[con.ID]; !exist {
-				return
-			}
-			con.logger.Info("Selected as DKG set", "round", nextRound)
-			con.cfgModule.registerDKG(nextRound, utils.GetDKGThreshold(config))
-			con.event.RegisterHeight(startHeight+config.RoundLength*2/3,
-				func(uint64) {
-					func() {
-						con.dkgReady.L.Lock()
-						defer con.dkgReady.L.Unlock()
-						con.dkgRunning = 0
-					}()
-					nextConfig := utils.GetConfigWithPanic(
-						con.gov, nextRound, con.logger)
-					con.runDKG(nextRound, nextConfig)
-				})
-		}(round + 1)
-	})
-	// Prepare blockChain module for next round and next "initialRound" routine.
-	con.event.RegisterHeight(startHeight+config.RoundLength, func(uint64) {
-		// Change round.
-		// Get configuration for next round.
-		nextRound := round + 1
-		nextConfig := utils.GetConfigWithPanic(con.gov, nextRound, con.logger)
-		con.initialRound(
-			startHeight+config.RoundLength, nextRound, nextConfig)
-	})
-	// Touch nodeSetCache for next round.
-	con.event.RegisterHeight(startHeight+config.RoundLength*9/10, func(uint64) {
-		go func() {
-			// TODO(jimmy): check DKGResetCount and do not touch if nextRound is reset.
-			if err := con.nodeSetCache.Touch(round + 1); err != nil {
-				con.logger.Warn("Failed to update nodeSetCache",
-					"round", round+1, "error", err)
-			}
-			if _, _, err := con.bcModule.vGetter.UpdateAndGet(round + 1); err != nil {
-				con.logger.Warn("Failed to update tsigVerifierCache",
-					"round", round+1, "error", err)
-			}
-		}()
-	})
-}
-
 // Stop the Consensus core.
 func (con *Consensus) Stop() {
 	con.ctxCancel()
 	con.baMgr.stop()
 	con.event.Reset()
 	con.waitGroup.Wait()
+	if nbApp, ok := con.app.(*nonBlocking); ok {
+		fmt.Println("Stopping nonBlocking App")
+		nbApp.wait()
+	}
 }
 
 func (con *Consensus) deliverNetworkMsg() {
@@ -1014,62 +1015,64 @@ func (con *Consensus) ProcessAgreementResult(
 	con.logger.Debug("Rebroadcast AgreementResult",
 		"result", rand)
 	con.network.BroadcastAgreementResult(rand)
+	go con.prepareRandomnessResult(rand)
+	return nil
+}
 
-	go func() {
-		dkgSet, err := con.nodeSetCache.GetDKGSet(rand.Position.Round)
-		if err != nil {
-			con.logger.Error("Failed to get dkg set",
-				"round", rand.Position.Round, "error", err)
-			return
-		}
-		if _, exist := dkgSet[con.ID]; !exist {
-			return
-		}
-		psig, err := con.cfgModule.preparePartialSignature(rand.Position.Round, rand.BlockHash)
-		if err != nil {
-			con.logger.Error("Failed to prepare psig",
-				"round", rand.Position.Round,
-				"hash", rand.BlockHash.String()[:6],
-				"error", err)
-			return
-		}
-		if err = con.signer.SignDKGPartialSignature(psig); err != nil {
-			con.logger.Error("Failed to sign psig",
+func (con *Consensus) prepareRandomnessResult(rand *types.AgreementResult) {
+	dkgSet, err := con.nodeSetCache.GetDKGSet(rand.Position.Round)
+	if err != nil {
+		con.logger.Error("Failed to get dkg set",
+			"round", rand.Position.Round, "error", err)
+		return
+	}
+	if _, exist := dkgSet[con.ID]; !exist {
+		return
+	}
+	con.logger.Debug("PrepareRandomness", "round", rand.Position.Round, "hash", rand.BlockHash)
+	psig, err := con.cfgModule.preparePartialSignature(rand.Position.Round, rand.BlockHash)
+	if err != nil {
+		con.logger.Error("Failed to prepare psig",
+			"round", rand.Position.Round,
+			"hash", rand.BlockHash.String()[:6],
+			"error", err)
+		return
+	}
+	if err = con.signer.SignDKGPartialSignature(psig); err != nil {
+		con.logger.Error("Failed to sign psig",
+			"hash", rand.BlockHash.String()[:6],
+			"error", err)
+		return
+	}
+	if err = con.cfgModule.processPartialSignature(psig); err != nil {
+		con.logger.Error("Failed process psig",
+			"hash", rand.BlockHash.String()[:6],
+			"error", err)
+		return
+	}
+	con.logger.Debug("Calling Network.BroadcastDKGPartialSignature",
+		"proposer", psig.ProposerID,
+		"round", psig.Round,
+		"hash", psig.Hash.String()[:6])
+	con.network.BroadcastDKGPartialSignature(psig)
+	tsig, err := con.cfgModule.runTSig(rand.Position.Round, rand.BlockHash)
+	if err != nil {
+		if err != ErrTSigAlreadyRunning {
+			con.logger.Error("Failed to run TSIG",
+				"position", rand.Position,
 				"hash", rand.BlockHash.String()[:6],
 				"error", err)
-			return
 		}
-		if err = con.cfgModule.processPartialSignature(psig); err != nil {
-			con.logger.Error("Failed process psig",
-				"hash", rand.BlockHash.String()[:6],
-				"error", err)
-			return
-		}
-		con.logger.Debug("Calling Network.BroadcastDKGPartialSignature",
-			"proposer", psig.ProposerID,
-			"round", psig.Round,
-			"hash", psig.Hash.String()[:6])
-		con.network.BroadcastDKGPartialSignature(psig)
-		tsig, err := con.cfgModule.runTSig(rand.Position.Round, rand.BlockHash)
-		if err != nil {
-			if err != ErrTSigAlreadyRunning {
-				con.logger.Error("Failed to run TSIG",
-					"position", rand.Position,
-					"hash", rand.BlockHash.String()[:6],
-					"error", err)
-			}
-			return
-		}
-		result := &types.BlockRandomnessResult{
-			BlockHash:  rand.BlockHash,
-			Position:   rand.Position,
-			Randomness: tsig.Signature,
-		}
-		// ProcessBlockRandomnessResult is not thread-safe so we put the result in
-		// the message channnel to be processed in the main thread.
-		con.msgChan <- result
-	}()
-	return nil
+		return
+	}
+	result := &types.BlockRandomnessResult{
+		BlockHash:  rand.BlockHash,
+		Position:   rand.Position,
+		Randomness: tsig.Signature,
+	}
+	// ProcessBlockRandomnessResult is not thread-safe so we put the result in
+	// the message channnel to be processed in the main thread.
+	con.msgChan <- result
 }
 
 // ProcessBlockRandomnessResult processes the randomness result.
@@ -1094,14 +1097,6 @@ func (con *Consensus) ProcessBlockRandomnessResult(
 
 // preProcessBlock performs Byzantine Agreement on the block.
 func (con *Consensus) preProcessBlock(b *types.Block) (err error) {
-	var exist bool
-	exist, err = con.nodeSetCache.Exists(b.Position.Round, b.ProposerID)
-	if err != nil {
-		return
-	}
-	if !exist {
-		return ErrProposerNotInNodeSet
-	}
 	err = con.baMgr.processBlock(b)
 	if err == nil && con.debugApp != nil {
 		con.debugApp.BlockReceived(b.Hash)
@@ -1137,7 +1132,10 @@ func (con *Consensus) deliveryGuard() {
 	defer con.waitGroup.Done()
 	time.Sleep(con.dMoment.Sub(time.Now()))
 	// Node takes time to start.
-	time.Sleep(60 * time.Second)
+	select {
+	case <-con.ctx.Done():
+	case <-time.After(60 * time.Second):
+	}
 	for {
 		select {
 		case <-con.ctx.Done():
@@ -1176,24 +1174,6 @@ func (con *Consensus) deliverBlock(b *types.Block) {
 	con.cfgModule.untouchTSigHash(b.Hash)
 	con.logger.Debug("Calling Application.BlockDelivered", "block", b)
 	con.app.BlockDelivered(b.Hash, b.Position, b.Finalization.Clone())
-	if b.Position.Round == con.roundForNewConfig {
-		// Get configuration for the round next to next round. Configuration
-		// for that round should be ready at this moment and is required for
-		// blockChain module. This logic is related to:
-		//  - roundShift
-		//  - notifyGenesisRound
-		futureRound := con.roundForNewConfig + 1
-		futureConfig := utils.GetConfigWithPanic(con.gov, futureRound, con.logger)
-		con.logger.Debug("Append Config", "round", futureRound)
-		if err := con.bcModule.appendConfig(
-			futureRound, futureConfig); err != nil {
-			con.logger.Debug("Unable to append config",
-				"round", futureRound,
-				"error", err)
-			panic(err)
-		}
-		con.roundForNewConfig++
-	}
 	if con.debugApp != nil {
 		con.debugApp.BlockReady(b.Hash)
 	}
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/interfaces.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/interfaces.go
index 45a1fc7d5..ddd6c3bb9 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/interfaces.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/interfaces.go
@@ -101,8 +101,12 @@ type Governance interface {
 	// Return the genesis configuration if round == 0.
 	Configuration(round uint64) *types.Config
 
-	// CRS returns the CRS for a given round.
-	// Return the genesis CRS if round == 0.
+	// CRS returns the CRS for a given round. Return the genesis CRS if
+	// round == 0.
+	//
+	// The CRS returned is the proposed or latest reseted one, it would be
+	// changed later if corresponding DKG set failed to generate group public
+	// key.
 	CRS(round uint64) common.Hash
 
 	// Propose a CRS of round.
@@ -162,3 +166,12 @@ type Ticker interface {
 	// Retart the ticker and clear all internal data.
 	Restart()
 }
+
+// Recovery interface for interacting with recovery information.
+type Recovery interface {
+	// ProposeSkipBlock proposes a skip block.
+	ProposeSkipBlock(height uint64) error
+
+	// Votes gets the number of votes of given height.
+	Votes(height uint64) (uint64, error)
+}
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/consensus.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/consensus.go
index 25911ce5f..f2f8f9e66 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/consensus.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/consensus.go
@@ -69,12 +69,14 @@ type Consensus struct {
 	configs           []*types.Config
 	roundBeginHeights []uint64
 	agreementRoundCut uint64
+	heightEvt         *common.Event
+	roundEvt          *utils.RoundEvent
 
 	// lock for accessing all fields.
 	lock               sync.RWMutex
 	duringBuffering    bool
 	latestCRSRound     uint64
-	moduleWaitGroup    sync.WaitGroup
+	waitGroup          sync.WaitGroup
 	agreementWaitGroup sync.WaitGroup
 	pullChan           chan common.Hash
 	receiveChan        chan *types.Block
@@ -82,6 +84,7 @@ type Consensus struct {
 	ctxCancel          context.CancelFunc
 	syncedLastBlock    *types.Block
 	syncedConsensus    *core.Consensus
+	syncedSkipNext     bool
 	dummyCancel        context.CancelFunc
 	dummyFinished      <-chan struct{}
 	dummyMsgBuffer     []interface{}
@@ -115,6 +118,7 @@ func NewConsensus(
 		receiveChan:       make(chan *types.Block, 1000),
 		pullChan:          make(chan common.Hash, 1000),
 		randomnessResults: make(map[common.Hash]*types.BlockRandomnessResult),
+		heightEvt:         common.NewEvent(),
 	}
 	con.ctx, con.ctxCancel = context.WithCancel(context.Background())
 	_, con.initChainTipHeight = db.GetCompactionChainTipInfo()
@@ -142,9 +146,73 @@ func (con *Consensus) assureBuffering() {
 		return
 	}
 	con.duringBuffering = true
+	// Get latest block to prepare utils.RoundEvent.
+	var (
+		err               error
+		blockHash, height = con.db.GetCompactionChainTipInfo()
+	)
+	if height == 0 {
+		con.roundEvt, err = utils.NewRoundEvent(con.ctx, con.gov, con.logger,
+			uint64(0), uint64(0), uint64(0), core.ConfigRoundShift)
+	} else {
+		var b types.Block
+		if b, err = con.db.GetBlock(blockHash); err == nil {
+			beginHeight := con.roundBeginHeights[b.Position.Round]
+			con.roundEvt, err = utils.NewRoundEvent(con.ctx, con.gov,
+				con.logger, b.Position.Round, beginHeight, beginHeight,
+				core.ConfigRoundShift)
+		}
+	}
+	if err != nil {
+		panic(err)
+	}
+	// Make sure con.roundEvt stopped before stopping con.agreementModule.
+	con.waitGroup.Add(1)
+	// Register a round event handler to notify CRS to agreementModule.
+	con.roundEvt.Register(func(evts []utils.RoundEventParam) {
+		con.waitGroup.Add(1)
+		go func() {
+			defer con.waitGroup.Done()
+			for _, e := range evts {
+				select {
+				case <-con.ctx.Done():
+					return
+				default:
+				}
+				for func() bool {
+					select {
+					case <-con.ctx.Done():
+						return false
+					case con.agreementModule.inputChan <- e.Round:
+						return false
+					case <-time.After(500 * time.Millisecond):
+						con.logger.Warn(
+							"agreement input channel is full when putting CRS",
+							"round", e.Round,
+						)
+						return true
+					}
+				}() {
+				}
+			}
+		}()
+	})
+	// Register a round event handler to validate next round.
+	con.roundEvt.Register(func(evts []utils.RoundEventParam) {
+		e := evts[len(evts)-1]
+		con.heightEvt.RegisterHeight(e.NextRoundValidationHeight(), func(
+			blockHeight uint64) {
+			select {
+			case <-con.ctx.Done():
+				return
+			default:
+			}
+			con.roundEvt.ValidateNextRound(blockHeight)
+		})
+	})
+	con.roundEvt.TriggerInitEvent()
 	con.startAgreement()
 	con.startNetwork()
-	con.startCRSMonitor()
 }
 
 func (con *Consensus) checkIfSynced(blocks []*types.Block) (synced bool) {
@@ -180,6 +248,29 @@ func (con *Consensus) buildAllEmptyBlocks() {
 	}
 }
 
+// ForceSync forces syncer to become synced.
+func (con *Consensus) ForceSync(skip bool) {
+	if con.syncedLastBlock != nil {
+		return
+	}
+	hash, _ := con.db.GetCompactionChainTipInfo()
+	var block types.Block
+	block, err := con.db.GetBlock(hash)
+	if err != nil {
+		panic(err)
+	}
+	con.logger.Info("Force Sync", "block", &block)
+	con.setupConfigsUntilRound(block.Position.Round + core.ConfigRoundShift - 1)
+	con.syncedLastBlock = &block
+	con.stopBuffering()
+	con.dummyCancel, con.dummyFinished = utils.LaunchDummyReceiver(
+		context.Background(), con.network.ReceiveChan(),
+		func(msg interface{}) {
+			con.dummyMsgBuffer = append(con.dummyMsgBuffer, msg)
+		})
+	con.syncedSkipNext = skip
+}
+
 // SyncBlocks syncs blocks from compaction chain, latest is true if the caller
 // regards the blocks are the latest ones. Notice that latest can be true for
 // many times.
@@ -241,6 +332,7 @@ func (con *Consensus) SyncBlocks(
 			b.Hash, b.Finalization.Height); err != nil {
 			return
 		}
+		go con.heightEvt.NotifyHeight(b.Finalization.Height)
 	}
 	if latest {
 		con.assureBuffering()
@@ -279,6 +371,7 @@ func (con *Consensus) GetSyncedConsensus() (*core.Consensus, error) {
 	con.syncedConsensus, err = core.NewConsensusFromSyncer(
 		con.syncedLastBlock,
 		con.roundBeginHeights[con.syncedLastBlock.Position.Round],
+		con.syncedSkipNext,
 		con.dMoment,
 		con.app,
 		con.gov,
@@ -321,7 +414,10 @@ func (con *Consensus) stopBuffering() {
 		return
 	}
 	con.logger.Trace("stop syncer modules")
-	con.moduleWaitGroup.Wait()
+	con.roundEvt.Stop()
+	con.waitGroup.Done()
+	// Wait for all routines depends on con.agreementModule stopped.
+	con.waitGroup.Wait()
 	// Since there is no one waiting for the receive channel of fullnode, we
 	// need to launch a dummy receiver right away.
 	con.dummyCancel, con.dummyFinished = utils.LaunchDummyReceiver(
@@ -467,9 +563,9 @@ func (con *Consensus) cacheRandomnessResult(r *types.BlockRandomnessResult) {
 
 // startNetwork starts network for receiving blocks and agreement results.
 func (con *Consensus) startNetwork() {
-	con.moduleWaitGroup.Add(1)
+	con.waitGroup.Add(1)
 	go func() {
-		defer con.moduleWaitGroup.Done()
+		defer con.waitGroup.Done()
 	loop:
 		for {
 			select {
@@ -497,62 +593,6 @@ func (con *Consensus) startNetwork() {
 	}()
 }
 
-// startCRSMonitor is the dummiest way to verify if the CRS for one round
-// is ready or not.
-func (con *Consensus) startCRSMonitor() {
-	var lastNotifiedRound uint64
-	// Notify all agreements for new CRS.
-	notifyNewCRS := func(round uint64) {
-		con.setupConfigsUntilRound(round)
-		if round == lastNotifiedRound {
-			return
-		}
-		con.logger.Debug("CRS is ready", "round", round)
-		lastNotifiedRound = round
-		func() {
-			con.lock.Lock()
-			defer con.lock.Unlock()
-			con.latestCRSRound = round
-		}()
-		for func() bool {
-			select {
-			case <-con.ctx.Done():
-				return false
-			case con.agreementModule.inputChan <- round:
-				return false
-			case <-time.After(500 * time.Millisecond):
-				con.logger.Debug(
-					"agreement input channel is full when putting CRS",
-					"round", round,
-				)
-				return true
-			}
-		}() {
-		}
-	}
-	con.moduleWaitGroup.Add(1)
-	go func() {
-		defer con.moduleWaitGroup.Done()
-		for {
-			select {
-			case <-con.ctx.Done():
-				return
-			case <-time.After(500 * time.Millisecond):
-			}
-			// Notify agreement modules for the latest round that CRS is
-			// available if the round is not notified yet.
-			checked := lastNotifiedRound + 1
-			for (con.gov.CRS(checked) != common.Hash{}) {
-				checked++
-			}
-			checked--
-			if checked > lastNotifiedRound {
-				notifyNewCRS(checked)
-			}
-		}
-	}()
-}
-
 func (con *Consensus) stopAgreement() {
 	if con.agreementModule.inputChan != nil {
 		close(con.agreementModule.inputChan)
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/watch-cat.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/watch-cat.go
new file mode 100644
index 000000000..d08bff9e9
--- /dev/null
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/syncer/watch-cat.go
@@ -0,0 +1,148 @@
+// Copyright 2019 The dexon-consensus Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core 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 dexon-consensus-core 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 dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package syncer
+
+import (
+	"context"
+	"time"
+
+	"github.com/dexon-foundation/dexon-consensus/common"
+	"github.com/dexon-foundation/dexon-consensus/core"
+	"github.com/dexon-foundation/dexon-consensus/core/types"
+	"github.com/dexon-foundation/dexon-consensus/core/utils"
+)
+
+type configReader interface {
+	Configuration(round uint64) *types.Config
+}
+
+// WatchCat is reponsible for signaling if syncer object should be terminated.
+type WatchCat struct {
+	recovery     core.Recovery
+	timeout      time.Duration
+	configReader configReader
+	feed         chan types.Position
+	polling      time.Duration
+	ctx          context.Context
+	cancel       context.CancelFunc
+	logger       common.Logger
+}
+
+// NewWatchCat creats a new WatchCat 🐱 object.
+func NewWatchCat(
+	recovery core.Recovery,
+	configReader configReader,
+	polling time.Duration,
+	timeout time.Duration,
+	logger common.Logger) *WatchCat {
+	wc := &WatchCat{
+		recovery:     recovery,
+		timeout:      timeout,
+		configReader: configReader,
+		feed:         make(chan types.Position),
+		polling:      polling,
+		logger:       logger,
+	}
+	return wc
+}
+
+// Feed the WatchCat so it won't produce the termination signal.
+func (wc *WatchCat) Feed(position types.Position) {
+	wc.feed <- position
+}
+
+// Start the WatchCat.
+func (wc *WatchCat) Start() {
+	wc.Stop()
+	wc.ctx, wc.cancel = context.WithCancel(context.Background())
+	go func() {
+		var lastPos types.Position
+	MonitorLoop:
+		for {
+			select {
+			case <-wc.ctx.Done():
+				return
+			default:
+			}
+			select {
+			case <-wc.ctx.Done():
+				return
+			case pos := <-wc.feed:
+				if !pos.Newer(lastPos) {
+					wc.logger.Warn("Feed with older height",
+						"pos", pos, "lastPos", lastPos)
+					continue
+				}
+				lastPos = pos
+			case <-time.After(wc.timeout):
+				break MonitorLoop
+			}
+		}
+		go func() {
+			for {
+				select {
+				case <-wc.ctx.Done():
+					return
+				case <-wc.feed:
+				}
+			}
+		}()
+		defer wc.cancel()
+		proposed := false
+		threshold := uint64(
+			utils.GetConfigWithPanic(wc.configReader, lastPos.Round, wc.logger).
+				NotarySetSize / 2)
+		wc.logger.Info("Threshold for recovery", "votes", threshold)
+	ResetLoop:
+		for {
+			if !proposed {
+				wc.logger.Info("Calling Recovery.ProposeSkipBlock",
+					"height", lastPos.Height)
+				if err := wc.recovery.ProposeSkipBlock(lastPos.Height); err != nil {
+					wc.logger.Warn("Failed to proposeSkipBlock", "height", lastPos.Height, "error", err)
+				} else {
+					proposed = true
+				}
+			}
+			votes, err := wc.recovery.Votes(lastPos.Height)
+			if err != nil {
+				wc.logger.Error("Failed to get recovery votes", "height", lastPos.Height, "error", err)
+			} else if votes > threshold {
+				wc.logger.Info("Threshold for recovery reached!")
+				break ResetLoop
+			}
+			select {
+			case <-wc.ctx.Done():
+				return
+			case <-time.After(wc.polling):
+			}
+		}
+	}()
+}
+
+// Stop the WatchCat.
+func (wc *WatchCat) Stop() {
+	if wc.cancel != nil {
+		wc.cancel()
+	}
+}
+
+// Meow return a closed channel if syncer should be terminated.
+func (wc *WatchCat) Meow() <-chan struct{} {
+	return wc.ctx.Done()
+}
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils.go
index f7dee757f..5742d113a 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils.go
@@ -236,14 +236,14 @@ func checkWithCancel(parentCtx context.Context, interval time.Duration,
 	defer cancel()
 Loop:
 	for {
+		if ret = checker(); ret {
+			return
+		}
 		select {
 		case <-ctx.Done():
 			break Loop
 		case <-time.After(interval):
 		}
-		if ret = checker(); ret {
-			return
-		}
 	}
 	return
 }
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/round-event.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/round-event.go
index bab1d32d2..1ce877dda 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/round-event.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/round-event.go
@@ -28,15 +28,15 @@ import (
 	typesDKG "github.com/dexon-foundation/dexon-consensus/core/types/dkg"
 )
 
-// ErrUnmatchedBlockHeightWithGov is for invalid parameters for NewRoundEvent.
-type ErrUnmatchedBlockHeightWithGov struct {
+// ErrUnmatchedBlockHeightWithConfig is for invalid parameters for NewRoundEvent.
+type ErrUnmatchedBlockHeightWithConfig struct {
 	round       uint64
 	reset       uint64
 	blockHeight uint64
 }
 
-func (e ErrUnmatchedBlockHeightWithGov) Error() string {
-	return fmt.Sprintf("unsynced block height and gov: round:%d reset:%d h:%d",
+func (e ErrUnmatchedBlockHeightWithConfig) Error() string {
+	return fmt.Sprintf("unsynced block height and cfg: round:%d reset:%d h:%d",
 		e.round, e.reset, e.blockHeight)
 }
 
@@ -56,11 +56,43 @@ type RoundEventParam struct {
 	CRS common.Hash
 }
 
-// NextRoundCheckpoint returns the height to check if the next round is ready.
-func (e RoundEventParam) NextRoundCheckpoint() uint64 {
+// NextRoundValidationHeight returns the height to check if the next round is
+// ready.
+func (e RoundEventParam) NextRoundValidationHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength*9/10
+}
+
+// NextCRSProposingHeight returns the height to propose CRS for next round.
+func (e RoundEventParam) NextCRSProposingHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength/2
+}
+
+// NextDKGPreparationHeight returns the height to prepare DKG set for next
+// round.
+func (e RoundEventParam) NextDKGPreparationHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength*2/3
+}
+
+// NextRoundHeight returns the height of the beginning of next round.
+func (e RoundEventParam) NextRoundHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength
+}
+
+// NextTouchNodeSetCacheHeight returns the height to touch the node set cache.
+func (e RoundEventParam) NextTouchNodeSetCacheHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength*9/10
+}
+
+// NextDKGResetHeight returns the height to reset DKG for next period.
+func (e RoundEventParam) NextDKGResetHeight() uint64 {
 	return e.BeginHeight + e.Config.RoundLength*8/10
 }
 
+// NextDKGRegisterHeight returns the height to register DKG.
+func (e RoundEventParam) NextDKGRegisterHeight() uint64 {
+	return e.BeginHeight + e.Config.RoundLength/2
+}
+
 // roundEventFn defines the fingerprint of handlers of round events.
 type roundEventFn func([]RoundEventParam)
 
@@ -131,7 +163,7 @@ func NewRoundEvent(parentCtx context.Context, gov governanceAccessor,
 		e.config.ExtendLength()
 	}
 	if !e.config.Contains(initBlockHeight) {
-		return nil, ErrUnmatchedBlockHeightWithGov{
+		return nil, ErrUnmatchedBlockHeightWithConfig{
 			round:       initRound,
 			reset:       resetCount,
 			blockHeight: initBlockHeight,
@@ -149,6 +181,22 @@ func (e *RoundEvent) Register(h roundEventFn) {
 	e.handlers = append(e.handlers, h)
 }
 
+// TriggerInitEvent triggers event from the initial setting.
+func (e *RoundEvent) TriggerInitEvent() {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	events := []RoundEventParam{RoundEventParam{
+		Round:       e.lastTriggeredRound,
+		Reset:       e.lastTriggeredResetCount,
+		BeginHeight: e.config.LastPeriodBeginHeight(),
+		CRS:         GetCRSWithPanic(e.gov, e.lastTriggeredRound, e.logger),
+		Config:      GetConfigWithPanic(e.gov, e.lastTriggeredRound, e.logger),
+	}}
+	for _, h := range e.handlers {
+		h(events)
+	}
+}
+
 // ValidateNextRound validate if the DKG set for next round is ready to go or
 // failed to setup, all registered handlers would be called once some decision
 // is made on chain.
@@ -225,14 +273,6 @@ func (e *RoundEvent) check(blockHeight, startRound uint64, lastDKGCheck bool) (
 			"crs", param.CRS.String()[:6],
 		)
 	}()
-	// Make sure current last config covers the blockHeight.
-	if !e.config.Contains(blockHeight) {
-		panic(ErrUnmatchedBlockHeightWithGov{
-			round:       e.lastTriggeredRound,
-			reset:       e.lastTriggeredResetCount,
-			blockHeight: blockHeight,
-		})
-	}
 	nextRound := e.lastTriggeredRound + 1
 	if nextRound >= startRound+e.roundShift {
 		// Avoid access configuration newer than last confirmed one over
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/utils.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/utils.go
index b8bd95ec4..14687d6ac 100644
--- a/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/utils.go
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/utils/utils.go
@@ -138,3 +138,9 @@ func LaunchDummyReceiver(
 func GetDKGThreshold(config *types.Config) int {
 	return int(config.DKGSetSize/3) + 1
 }
+
+// GetNextRoundValidationHeight returns the block height to check if the next
+// round is ready.
+func GetNextRoundValidationHeight(begin, length uint64) uint64 {
+	return begin + length*9/10
+}
diff --git a/vendor/github.com/onrik/ethrpc/LICENSE b/vendor/github.com/onrik/ethrpc/LICENSE
new file mode 100644
index 000000000..c8162bd91
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 Andrey
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/vendor/github.com/onrik/ethrpc/README.md b/vendor/github.com/onrik/ethrpc/README.md
new file mode 100644
index 000000000..c273e8931
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/README.md
@@ -0,0 +1,103 @@
+# Ethrpc
+[![Build Status](https://travis-ci.org/onrik/ethrpc.svg?branch=master)](https://travis-ci.org/onrik/ethrpc)
+[![Coverage Status](https://coveralls.io/repos/github/onrik/ethrpc/badge.svg?branch=master)](https://coveralls.io/github/onrik/ethrpc?branch=master)
+[![Go Report Card](https://goreportcard.com/badge/github.com/onrik/ethrpc)](https://goreportcard.com/report/github.com/onrik/ethrpc)
+[![GoDoc](https://godoc.org/github.com/onrik/ethrpc?status.svg)](https://godoc.org/github.com/onrik/ethrpc)
+[![Donate with Ethereum](https://en.cryptobadges.io/badge/micro/0xf4144308d6D67A1F00a61A596c0eB7B08411344a)](https://en.cryptobadges.io/donate/0xf4144308d6D67A1F00a61A596c0eB7B08411344a)
+
+Golang client for ethereum [JSON RPC API](https://github.com/ethereum/wiki/wiki/JSON-RPC).
+
+- [x] web3_clientVersion
+- [x] web3_sha3
+- [x] net_version
+- [x] net_peerCount
+- [x] net_listening
+- [x] eth_protocolVersion
+- [x] eth_syncing
+- [x] eth_coinbase
+- [x] eth_mining
+- [x] eth_hashrate
+- [x] eth_gasPrice
+- [x] eth_accounts
+- [x] eth_blockNumber
+- [x] eth_getBalance
+- [x] eth_getStorageAt
+- [x] eth_getTransactionCount
+- [x] eth_getBlockTransactionCountByHash
+- [x] eth_getBlockTransactionCountByNumber
+- [x] eth_getUncleCountByBlockHash
+- [x] eth_getUncleCountByBlockNumber
+- [x] eth_getCode
+- [x] eth_sign
+- [x] eth_sendTransaction
+- [x] eth_sendRawTransaction
+- [x] eth_call
+- [x] eth_estimateGas
+- [x] eth_getBlockByHash
+- [x] eth_getBlockByNumber
+- [x] eth_getTransactionByHash
+- [x] eth_getTransactionByBlockHashAndIndex
+- [x] eth_getTransactionByBlockNumberAndIndex
+- [x] eth_getTransactionReceipt
+- [ ] eth_getUncleByBlockHashAndIndex
+- [ ] eth_getUncleByBlockNumberAndIndex
+- [x] eth_getCompilers
+- [ ] eth_compileLLL
+- [ ] eth_compileSolidity
+- [ ] eth_compileSerpent
+- [x] eth_newFilter
+- [x] eth_newBlockFilter
+- [x] eth_newPendingTransactionFilter
+- [x] eth_uninstallFilter
+- [x] eth_getFilterChanges
+- [x] eth_getFilterLogs
+- [x] eth_getLogs
+- [ ] eth_getWork
+- [ ] eth_submitWork
+- [ ] eth_submitHashrate
+- [ ] shh_post
+- [ ] shh_version
+- [ ] shh_newIdentity
+- [ ] shh_hasIdentity
+- [ ] shh_newGroup
+- [ ] shh_addToGroup
+- [ ] shh_newFilter
+- [ ] shh_uninstallFilter
+- [ ] shh_getFilterChanges
+- [ ] shh_getMessages
+
+##### Usage:
+```go
+package main
+
+import (
+    "fmt"
+    "log"
+
+    "github.com/onrik/ethrpc"
+)
+
+func main() {
+    client := ethrpc.New("http://127.0.0.1:8545")
+
+    version, err := client.Web3ClientVersion()
+    if err != nil {
+        log.Fatal(err)
+    }
+    fmt.Println(version)
+
+    // Send 1 eth
+    txid, err := client.EthSendTransaction(ethrpc.T{
+        From:  "0x6247cf0412c6462da2a51d05139e2a3c6c630f0a",
+        To:    "0xcfa202c4268749fbb5136f2b68f7402984ed444b",
+        Value: ethrpc.Eth1(),
+    })
+    if err != nil {
+        log.Fatal(err)
+    }
+    fmt.Println(txid)
+}
+```
+
+[![Donate with Ethereum](https://en.cryptobadges.io/badge/big/0xf4144308d6D67A1F00a61A596c0eB7B08411344a?showBalance=true)](https://en.cryptobadges.io/donate/0xf4144308d6D67A1F00a61A596c0eB7B08411344a)
+
diff --git a/vendor/github.com/onrik/ethrpc/ethrpc.go b/vendor/github.com/onrik/ethrpc/ethrpc.go
new file mode 100644
index 000000000..5118b425d
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/ethrpc.go
@@ -0,0 +1,514 @@
+package ethrpc
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/big"
+	"net/http"
+	"os"
+)
+
+// EthError - ethereum error
+type EthError struct {
+	Code    int    `json:"code"`
+	Message string `json:"message"`
+}
+
+func (err EthError) Error() string {
+	return fmt.Sprintf("Error %d (%s)", err.Code, err.Message)
+}
+
+type ethResponse struct {
+	ID      int             `json:"id"`
+	JSONRPC string          `json:"jsonrpc"`
+	Result  json.RawMessage `json:"result"`
+	Error   *EthError       `json:"error"`
+}
+
+type ethRequest struct {
+	ID      int           `json:"id"`
+	JSONRPC string        `json:"jsonrpc"`
+	Method  string        `json:"method"`
+	Params  []interface{} `json:"params"`
+}
+
+// EthRPC - Ethereum rpc client
+type EthRPC struct {
+	url    string
+	client httpClient
+	log    logger
+	Debug  bool
+}
+
+// New create new rpc client with given url
+func New(url string, options ...func(rpc *EthRPC)) *EthRPC {
+	rpc := &EthRPC{
+		url:    url,
+		client: http.DefaultClient,
+		log:    log.New(os.Stderr, "", log.LstdFlags),
+	}
+	for _, option := range options {
+		option(rpc)
+	}
+
+	return rpc
+}
+
+// NewEthRPC create new rpc client with given url
+func NewEthRPC(url string, options ...func(rpc *EthRPC)) *EthRPC {
+	return New(url, options...)
+}
+
+func (rpc *EthRPC) call(method string, target interface{}, params ...interface{}) error {
+	result, err := rpc.Call(method, params...)
+	if err != nil {
+		return err
+	}
+
+	if target == nil {
+		return nil
+	}
+
+	return json.Unmarshal(result, target)
+}
+
+// URL returns client url
+func (rpc *EthRPC) URL() string {
+	return rpc.url
+}
+
+// Call returns raw response of method call
+func (rpc *EthRPC) Call(method string, params ...interface{}) (json.RawMessage, error) {
+	request := ethRequest{
+		ID:      1,
+		JSONRPC: "2.0",
+		Method:  method,
+		Params:  params,
+	}
+
+	body, err := json.Marshal(request)
+	if err != nil {
+		return nil, err
+	}
+
+	response, err := rpc.client.Post(rpc.url, "application/json", bytes.NewBuffer(body))
+	if response != nil {
+		defer response.Body.Close()
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	if rpc.Debug {
+		rpc.log.Println(fmt.Sprintf("%s\nRequest: %s\nResponse: %s\n", method, body, data))
+	}
+
+	resp := new(ethResponse)
+	if err := json.Unmarshal(data, resp); err != nil {
+		return nil, err
+	}
+
+	if resp.Error != nil {
+		return nil, *resp.Error
+	}
+
+	return resp.Result, nil
+
+}
+
+// RawCall returns raw response of method call (Deprecated)
+func (rpc *EthRPC) RawCall(method string, params ...interface{}) (json.RawMessage, error) {
+	return rpc.Call(method, params...)
+}
+
+// Web3ClientVersion returns the current client version.
+func (rpc *EthRPC) Web3ClientVersion() (string, error) {
+	var clientVersion string
+
+	err := rpc.call("web3_clientVersion", &clientVersion)
+	return clientVersion, err
+}
+
+// Web3Sha3 returns Keccak-256 (not the standardized SHA3-256) of the given data.
+func (rpc *EthRPC) Web3Sha3(data []byte) (string, error) {
+	var hash string
+
+	err := rpc.call("web3_sha3", &hash, fmt.Sprintf("0x%x", data))
+	return hash, err
+}
+
+// NetVersion returns the current network protocol version.
+func (rpc *EthRPC) NetVersion() (string, error) {
+	var version string
+
+	err := rpc.call("net_version", &version)
+	return version, err
+}
+
+// NetListening returns true if client is actively listening for network connections.
+func (rpc *EthRPC) NetListening() (bool, error) {
+	var listening bool
+
+	err := rpc.call("net_listening", &listening)
+	return listening, err
+}
+
+// NetPeerCount returns number of peers currently connected to the client.
+func (rpc *EthRPC) NetPeerCount() (int, error) {
+	var response string
+	if err := rpc.call("net_peerCount", &response); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthProtocolVersion returns the current ethereum protocol version.
+func (rpc *EthRPC) EthProtocolVersion() (string, error) {
+	var protocolVersion string
+
+	err := rpc.call("eth_protocolVersion", &protocolVersion)
+	return protocolVersion, err
+}
+
+// EthSyncing returns an object with data about the sync status or false.
+func (rpc *EthRPC) EthSyncing() (*Syncing, error) {
+	result, err := rpc.RawCall("eth_syncing")
+	if err != nil {
+		return nil, err
+	}
+	syncing := new(Syncing)
+	if bytes.Equal(result, []byte("false")) {
+		return syncing, nil
+	}
+	err = json.Unmarshal(result, syncing)
+	return syncing, err
+}
+
+// EthCoinbase returns the client coinbase address
+func (rpc *EthRPC) EthCoinbase() (string, error) {
+	var address string
+
+	err := rpc.call("eth_coinbase", &address)
+	return address, err
+}
+
+// EthMining returns true if client is actively mining new blocks.
+func (rpc *EthRPC) EthMining() (bool, error) {
+	var mining bool
+
+	err := rpc.call("eth_mining", &mining)
+	return mining, err
+}
+
+// EthHashrate returns the number of hashes per second that the node is mining with.
+func (rpc *EthRPC) EthHashrate() (int, error) {
+	var response string
+
+	if err := rpc.call("eth_hashrate", &response); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGasPrice returns the current price per gas in wei.
+func (rpc *EthRPC) EthGasPrice() (big.Int, error) {
+	var response string
+	if err := rpc.call("eth_gasPrice", &response); err != nil {
+		return big.Int{}, err
+	}
+
+	return ParseBigInt(response)
+}
+
+// EthAccounts returns a list of addresses owned by client.
+func (rpc *EthRPC) EthAccounts() ([]string, error) {
+	accounts := []string{}
+
+	err := rpc.call("eth_accounts", &accounts)
+	return accounts, err
+}
+
+// EthBlockNumber returns the number of most recent block.
+func (rpc *EthRPC) EthBlockNumber() (int, error) {
+	var response string
+	if err := rpc.call("eth_blockNumber", &response); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetBalance returns the balance of the account of given address in wei.
+func (rpc *EthRPC) EthGetBalance(address, block string) (big.Int, error) {
+	var response string
+	if err := rpc.call("eth_getBalance", &response, address, block); err != nil {
+		return big.Int{}, err
+	}
+
+	return ParseBigInt(response)
+}
+
+// EthGetStorageAt returns the value from a storage position at a given address.
+func (rpc *EthRPC) EthGetStorageAt(data string, position int, tag string) (string, error) {
+	var result string
+
+	err := rpc.call("eth_getStorageAt", &result, data, IntToHex(position), tag)
+	return result, err
+}
+
+// EthGetTransactionCount returns the number of transactions sent from an address.
+func (rpc *EthRPC) EthGetTransactionCount(address, block string) (int, error) {
+	var response string
+
+	if err := rpc.call("eth_getTransactionCount", &response, address, block); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetBlockTransactionCountByHash returns the number of transactions in a block from a block matching the given block hash.
+func (rpc *EthRPC) EthGetBlockTransactionCountByHash(hash string) (int, error) {
+	var response string
+
+	if err := rpc.call("eth_getBlockTransactionCountByHash", &response, hash); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetBlockTransactionCountByNumber returns the number of transactions in a block from a block matching the given block
+func (rpc *EthRPC) EthGetBlockTransactionCountByNumber(number int) (int, error) {
+	var response string
+
+	if err := rpc.call("eth_getBlockTransactionCountByNumber", &response, IntToHex(number)); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetUncleCountByBlockHash returns the number of uncles in a block from a block matching the given block hash.
+func (rpc *EthRPC) EthGetUncleCountByBlockHash(hash string) (int, error) {
+	var response string
+
+	if err := rpc.call("eth_getUncleCountByBlockHash", &response, hash); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetUncleCountByBlockNumber returns the number of uncles in a block from a block matching the given block number.
+func (rpc *EthRPC) EthGetUncleCountByBlockNumber(number int) (int, error) {
+	var response string
+
+	if err := rpc.call("eth_getUncleCountByBlockNumber", &response, IntToHex(number)); err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+// EthGetCode returns code at a given address.
+func (rpc *EthRPC) EthGetCode(address, block string) (string, error) {
+	var code string
+
+	err := rpc.call("eth_getCode", &code, address, block)
+	return code, err
+}
+
+// EthSign signs data with a given address.
+// Calculates an Ethereum specific signature with: sign(keccak256("\x19Ethereum Signed Message:\n" + len(message) + message)))
+func (rpc *EthRPC) EthSign(address, data string) (string, error) {
+	var signature string
+
+	err := rpc.call("eth_sign", &signature, address, data)
+	return signature, err
+}
+
+// EthSendTransaction creates new message call transaction or a contract creation, if the data field contains code.
+func (rpc *EthRPC) EthSendTransaction(transaction T) (string, error) {
+	var hash string
+
+	err := rpc.call("eth_sendTransaction", &hash, transaction)
+	return hash, err
+}
+
+// EthSendRawTransaction creates new message call transaction or a contract creation for signed transactions.
+func (rpc *EthRPC) EthSendRawTransaction(data string) (string, error) {
+	var hash string
+
+	err := rpc.call("eth_sendRawTransaction", &hash, data)
+	return hash, err
+}
+
+// EthCall executes a new message call immediately without creating a transaction on the block chain.
+func (rpc *EthRPC) EthCall(transaction T, tag string) (string, error) {
+	var data string
+
+	err := rpc.call("eth_call", &data, transaction, tag)
+	return data, err
+}
+
+// EthEstimateGas makes a call or transaction, which won't be added to the blockchain and returns the used gas, which can be used for estimating the used gas.
+func (rpc *EthRPC) EthEstimateGas(transaction T) (int, error) {
+	var response string
+
+	err := rpc.call("eth_estimateGas", &response, transaction)
+	if err != nil {
+		return 0, err
+	}
+
+	return ParseInt(response)
+}
+
+func (rpc *EthRPC) getBlock(method string, withTransactions bool, params ...interface{}) (*Block, error) {
+	result, err := rpc.RawCall(method, params...)
+	if err != nil {
+		return nil, err
+	}
+	if bytes.Equal(result, []byte("null")) {
+		return nil, nil
+	}
+
+	var response proxyBlock
+	if withTransactions {
+		response = new(proxyBlockWithTransactions)
+	} else {
+		response = new(proxyBlockWithoutTransactions)
+	}
+
+	err = json.Unmarshal(result, response)
+	if err != nil {
+		return nil, err
+	}
+
+	block := response.toBlock()
+	return &block, nil
+}
+
+// EthGetBlockByHash returns information about a block by hash.
+func (rpc *EthRPC) EthGetBlockByHash(hash string, withTransactions bool) (*Block, error) {
+	return rpc.getBlock("eth_getBlockByHash", withTransactions, hash, withTransactions)
+}
+
+// EthGetBlockByNumber returns information about a block by block number.
+func (rpc *EthRPC) EthGetBlockByNumber(number int, withTransactions bool) (*Block, error) {
+	return rpc.getBlock("eth_getBlockByNumber", withTransactions, IntToHex(number), withTransactions)
+}
+
+func (rpc *EthRPC) getTransaction(method string, params ...interface{}) (*Transaction, error) {
+	transaction := new(Transaction)
+
+	err := rpc.call(method, transaction, params...)
+	return transaction, err
+}
+
+// EthGetTransactionByHash returns the information about a transaction requested by transaction hash.
+func (rpc *EthRPC) EthGetTransactionByHash(hash string) (*Transaction, error) {
+	return rpc.getTransaction("eth_getTransactionByHash", hash)
+}
+
+// EthGetTransactionByBlockHashAndIndex returns information about a transaction by block hash and transaction index position.
+func (rpc *EthRPC) EthGetTransactionByBlockHashAndIndex(blockHash string, transactionIndex int) (*Transaction, error) {
+	return rpc.getTransaction("eth_getTransactionByBlockHashAndIndex", blockHash, IntToHex(transactionIndex))
+}
+
+// EthGetTransactionByBlockNumberAndIndex returns information about a transaction by block number and transaction index position.
+func (rpc *EthRPC) EthGetTransactionByBlockNumberAndIndex(blockNumber, transactionIndex int) (*Transaction, error) {
+	return rpc.getTransaction("eth_getTransactionByBlockNumberAndIndex", IntToHex(blockNumber), IntToHex(transactionIndex))
+}
+
+// EthGetTransactionReceipt returns the receipt of a transaction by transaction hash.
+// Note That the receipt is not available for pending transactions.
+func (rpc *EthRPC) EthGetTransactionReceipt(hash string) (*TransactionReceipt, error) {
+	transactionReceipt := new(TransactionReceipt)
+
+	err := rpc.call("eth_getTransactionReceipt", transactionReceipt, hash)
+	if err != nil {
+		return nil, err
+	}
+
+	return transactionReceipt, nil
+}
+
+// EthGetCompilers returns a list of available compilers in the client.
+func (rpc *EthRPC) EthGetCompilers() ([]string, error) {
+	compilers := []string{}
+
+	err := rpc.call("eth_getCompilers", &compilers)
+	return compilers, err
+}
+
+// EthNewFilter creates a new filter object.
+func (rpc *EthRPC) EthNewFilter(params FilterParams) (string, error) {
+	var filterID string
+	err := rpc.call("eth_newFilter", &filterID, params)
+	return filterID, err
+}
+
+// EthNewBlockFilter creates a filter in the node, to notify when a new block arrives.
+// To check if the state has changed, call EthGetFilterChanges.
+func (rpc *EthRPC) EthNewBlockFilter() (string, error) {
+	var filterID string
+	err := rpc.call("eth_newBlockFilter", &filterID)
+	return filterID, err
+}
+
+// EthNewPendingTransactionFilter creates a filter in the node, to notify when new pending transactions arrive.
+// To check if the state has changed, call EthGetFilterChanges.
+func (rpc *EthRPC) EthNewPendingTransactionFilter() (string, error) {
+	var filterID string
+	err := rpc.call("eth_newPendingTransactionFilter", &filterID)
+	return filterID, err
+}
+
+// EthUninstallFilter uninstalls a filter with given id.
+func (rpc *EthRPC) EthUninstallFilter(filterID string) (bool, error) {
+	var res bool
+	err := rpc.call("eth_uninstallFilter", &res, filterID)
+	return res, err
+}
+
+// EthGetFilterChanges polling method for a filter, which returns an array of logs which occurred since last poll.
+func (rpc *EthRPC) EthGetFilterChanges(filterID string) ([]Log, error) {
+	var logs = []Log{}
+	err := rpc.call("eth_getFilterChanges", &logs, filterID)
+	return logs, err
+}
+
+// EthGetFilterLogs returns an array of all logs matching filter with given id.
+func (rpc *EthRPC) EthGetFilterLogs(filterID string) ([]Log, error) {
+	var logs = []Log{}
+	err := rpc.call("eth_getFilterLogs", &logs, filterID)
+	return logs, err
+}
+
+// EthGetLogs returns an array of all logs matching a given filter object.
+func (rpc *EthRPC) EthGetLogs(params FilterParams) ([]Log, error) {
+	var logs = []Log{}
+	err := rpc.call("eth_getLogs", &logs, params)
+	return logs, err
+}
+
+// Eth1 returns 1 ethereum value (10^18 wei)
+func (rpc *EthRPC) Eth1() *big.Int {
+	return Eth1()
+}
+
+// Eth1 returns 1 ethereum value (10^18 wei)
+func Eth1() *big.Int {
+	return big.NewInt(1000000000000000000)
+}
diff --git a/vendor/github.com/onrik/ethrpc/go.mod b/vendor/github.com/onrik/ethrpc/go.mod
new file mode 100644
index 000000000..8f047b1d3
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/go.mod
@@ -0,0 +1 @@
+module github.com/onrik/ethrpc
diff --git a/vendor/github.com/onrik/ethrpc/helpers.go b/vendor/github.com/onrik/ethrpc/helpers.go
new file mode 100644
index 000000000..e98030055
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/helpers.go
@@ -0,0 +1,40 @@
+package ethrpc
+
+import (
+	"fmt"
+	"math/big"
+	"strconv"
+	"strings"
+)
+
+// ParseInt parse hex string value to int
+func ParseInt(value string) (int, error) {
+	i, err := strconv.ParseInt(strings.TrimPrefix(value, "0x"), 16, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	return int(i), nil
+}
+
+// ParseBigInt parse hex string value to big.Int
+func ParseBigInt(value string) (big.Int, error) {
+	i := big.Int{}
+	_, err := fmt.Sscan(value, &i)
+
+	return i, err
+}
+
+// IntToHex convert int to hexadecimal representation
+func IntToHex(i int) string {
+	return fmt.Sprintf("0x%x", i)
+}
+
+// BigToHex covert big.Int to hexadecimal representation
+func BigToHex(bigInt big.Int) string {
+	if bigInt.BitLen() == 0 {
+		return "0x0"
+	}
+
+	return "0x" + strings.TrimPrefix(fmt.Sprintf("%x", bigInt.Bytes()), "0")
+}
diff --git a/vendor/github.com/onrik/ethrpc/interface.go b/vendor/github.com/onrik/ethrpc/interface.go
new file mode 100644
index 000000000..2e3021d1b
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/interface.go
@@ -0,0 +1,50 @@
+package ethrpc
+
+import (
+	"math/big"
+)
+
+type EthereumAPI interface {
+	Web3ClientVersion() (string, error)
+	Web3Sha3(data []byte) (string, error)
+	NetVersion() (string, error)
+	NetListening() (bool, error)
+	NetPeerCount() (int, error)
+	EthProtocolVersion() (string, error)
+	EthSyncing() (*Syncing, error)
+	EthCoinbase() (string, error)
+	EthMining() (bool, error)
+	EthHashrate() (int, error)
+	EthGasPrice() (big.Int, error)
+	EthAccounts() ([]string, error)
+	EthBlockNumber() (int, error)
+	EthGetBalance(address, block string) (big.Int, error)
+	EthGetStorageAt(data string, position int, tag string) (string, error)
+	EthGetTransactionCount(address, block string) (int, error)
+	EthGetBlockTransactionCountByHash(hash string) (int, error)
+	EthGetBlockTransactionCountByNumber(number int) (int, error)
+	EthGetUncleCountByBlockHash(hash string) (int, error)
+	EthGetUncleCountByBlockNumber(number int) (int, error)
+	EthGetCode(address, block string) (string, error)
+	EthSign(address, data string) (string, error)
+	EthSendTransaction(transaction T) (string, error)
+	EthSendRawTransaction(data string) (string, error)
+	EthCall(transaction T, tag string) (string, error)
+	EthEstimateGas(transaction T) (int, error)
+	EthGetBlockByHash(hash string, withTransactions bool) (*Block, error)
+	EthGetBlockByNumber(number int, withTransactions bool) (*Block, error)
+	EthGetTransactionByHash(hash string) (*Transaction, error)
+	EthGetTransactionByBlockHashAndIndex(blockHash string, transactionIndex int) (*Transaction, error)
+	EthGetTransactionByBlockNumberAndIndex(blockNumber, transactionIndex int) (*Transaction, error)
+	EthGetTransactionReceipt(hash string) (*TransactionReceipt, error)
+	EthGetCompilers() ([]string, error)
+	EthNewFilter(params FilterParams) (string, error)
+	EthNewBlockFilter() (string, error)
+	EthNewPendingTransactionFilter() (string, error)
+	EthUninstallFilter(filterID string) (bool, error)
+	EthGetFilterChanges(filterID string) ([]Log, error)
+	EthGetFilterLogs(filterID string) ([]Log, error)
+	EthGetLogs(params FilterParams) ([]Log, error)
+}
+
+var _ EthereumAPI = (*EthRPC)(nil)
diff --git a/vendor/github.com/onrik/ethrpc/options.go b/vendor/github.com/onrik/ethrpc/options.go
new file mode 100644
index 000000000..72ab39879
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/options.go
@@ -0,0 +1,35 @@
+package ethrpc
+
+import (
+	"io"
+	"net/http"
+)
+
+type httpClient interface {
+	Post(url string, contentType string, body io.Reader) (*http.Response, error)
+}
+
+type logger interface {
+	Println(v ...interface{})
+}
+
+// WithHttpClient set custom http client
+func WithHttpClient(client httpClient) func(rpc *EthRPC) {
+	return func(rpc *EthRPC) {
+		rpc.client = client
+	}
+}
+
+// WithLogger set custom logger
+func WithLogger(l logger) func(rpc *EthRPC) {
+	return func(rpc *EthRPC) {
+		rpc.log = l
+	}
+}
+
+// WithDebug set debug flag
+func WithDebug(enabled bool) func(rpc *EthRPC) {
+	return func(rpc *EthRPC) {
+		rpc.Debug = enabled
+	}
+}
diff --git a/vendor/github.com/onrik/ethrpc/types.go b/vendor/github.com/onrik/ethrpc/types.go
new file mode 100644
index 000000000..b90baeef0
--- /dev/null
+++ b/vendor/github.com/onrik/ethrpc/types.go
@@ -0,0 +1,322 @@
+package ethrpc
+
+import (
+	"bytes"
+	"encoding/json"
+	"math/big"
+	"unsafe"
+)
+
+// Syncing - object with syncing data info
+type Syncing struct {
+	IsSyncing     bool
+	StartingBlock int
+	CurrentBlock  int
+	HighestBlock  int
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (s *Syncing) UnmarshalJSON(data []byte) error {
+	proxy := new(proxySyncing)
+	if err := json.Unmarshal(data, proxy); err != nil {
+		return err
+	}
+
+	proxy.IsSyncing = true
+	*s = *(*Syncing)(unsafe.Pointer(proxy))
+
+	return nil
+}
+
+// T - input transaction object
+type T struct {
+	From     string
+	To       string
+	Gas      int
+	GasPrice *big.Int
+	Value    *big.Int
+	Data     string
+	Nonce    int
+}
+
+// MarshalJSON implements the json.Unmarshaler interface.
+func (t T) MarshalJSON() ([]byte, error) {
+	params := map[string]interface{}{
+		"from": t.From,
+	}
+	if t.To != "" {
+		params["to"] = t.To
+	}
+	if t.Gas > 0 {
+		params["gas"] = IntToHex(t.Gas)
+	}
+	if t.GasPrice != nil {
+		params["gasPrice"] = BigToHex(*t.GasPrice)
+	}
+	if t.Value != nil {
+		params["value"] = BigToHex(*t.Value)
+	}
+	if t.Data != "" {
+		params["data"] = t.Data
+	}
+	if t.Nonce > 0 {
+		params["nonce"] = IntToHex(t.Nonce)
+	}
+
+	return json.Marshal(params)
+}
+
+// Transaction - transaction object
+type Transaction struct {
+	Hash             string
+	Nonce            int
+	BlockHash        string
+	BlockNumber      *int
+	TransactionIndex *int
+	From             string
+	To               string
+	Value            big.Int
+	Gas              int
+	GasPrice         big.Int
+	Input            string
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (t *Transaction) UnmarshalJSON(data []byte) error {
+	proxy := new(proxyTransaction)
+	if err := json.Unmarshal(data, proxy); err != nil {
+		return err
+	}
+
+	*t = *(*Transaction)(unsafe.Pointer(proxy))
+
+	return nil
+}
+
+// Log - log object
+type Log struct {
+	Removed          bool
+	LogIndex         int
+	TransactionIndex int
+	TransactionHash  string
+	BlockNumber      int
+	BlockHash        string
+	Address          string
+	Data             string
+	Topics           []string
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (log *Log) UnmarshalJSON(data []byte) error {
+	proxy := new(proxyLog)
+	if err := json.Unmarshal(data, proxy); err != nil {
+		return err
+	}
+
+	*log = *(*Log)(unsafe.Pointer(proxy))
+
+	return nil
+}
+
+// FilterParams - Filter parameters object
+type FilterParams struct {
+	FromBlock string     `json:"fromBlock,omitempty"`
+	ToBlock   string     `json:"toBlock,omitempty"`
+	Address   []string   `json:"address,omitempty"`
+	Topics    [][]string `json:"topics,omitempty"`
+}
+
+// TransactionReceipt - transaction receipt object
+type TransactionReceipt struct {
+	TransactionHash   string
+	TransactionIndex  int
+	BlockHash         string
+	BlockNumber       int
+	CumulativeGasUsed int
+	GasUsed           int
+	ContractAddress   string
+	Logs              []Log
+	LogsBloom         string
+	Root              string
+	Status            string
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (t *TransactionReceipt) UnmarshalJSON(data []byte) error {
+	proxy := new(proxyTransactionReceipt)
+	if err := json.Unmarshal(data, proxy); err != nil {
+		return err
+	}
+
+	*t = *(*TransactionReceipt)(unsafe.Pointer(proxy))
+
+	return nil
+}
+
+// Block - block object
+type Block struct {
+	Number           int
+	Hash             string
+	ParentHash       string
+	Nonce            string
+	Sha3Uncles       string
+	LogsBloom        string
+	TransactionsRoot string
+	StateRoot        string
+	Miner            string
+	Difficulty       big.Int
+	TotalDifficulty  big.Int
+	ExtraData        string
+	Size             int
+	GasLimit         int
+	GasUsed          int
+	Timestamp        int
+	Uncles           []string
+	Transactions     []Transaction
+}
+
+type proxySyncing struct {
+	IsSyncing     bool   `json:"-"`
+	StartingBlock hexInt `json:"startingBlock"`
+	CurrentBlock  hexInt `json:"currentBlock"`
+	HighestBlock  hexInt `json:"highestBlock"`
+}
+
+type proxyTransaction struct {
+	Hash             string  `json:"hash"`
+	Nonce            hexInt  `json:"nonce"`
+	BlockHash        string  `json:"blockHash"`
+	BlockNumber      *hexInt `json:"blockNumber"`
+	TransactionIndex *hexInt `json:"transactionIndex"`
+	From             string  `json:"from"`
+	To               string  `json:"to"`
+	Value            hexBig  `json:"value"`
+	Gas              hexInt  `json:"gas"`
+	GasPrice         hexBig  `json:"gasPrice"`
+	Input            string  `json:"input"`
+}
+
+type proxyLog struct {
+	Removed          bool     `json:"removed"`
+	LogIndex         hexInt   `json:"logIndex"`
+	TransactionIndex hexInt   `json:"transactionIndex"`
+	TransactionHash  string   `json:"transactionHash"`
+	BlockNumber      hexInt   `json:"blockNumber"`
+	BlockHash        string   `json:"blockHash"`
+	Address          string   `json:"address"`
+	Data             string   `json:"data"`
+	Topics           []string `json:"topics"`
+}
+
+type proxyTransactionReceipt struct {
+	TransactionHash   string `json:"transactionHash"`
+	TransactionIndex  hexInt `json:"transactionIndex"`
+	BlockHash         string `json:"blockHash"`
+	BlockNumber       hexInt `json:"blockNumber"`
+	CumulativeGasUsed hexInt `json:"cumulativeGasUsed"`
+	GasUsed           hexInt `json:"gasUsed"`
+	ContractAddress   string `json:"contractAddress,omitempty"`
+	Logs              []Log  `json:"logs"`
+	LogsBloom         string `json:"logsBloom"`
+	Root              string `json:"root"`
+	Status            string `json:"status,omitempty"`
+}
+
+type hexInt int
+
+func (i *hexInt) UnmarshalJSON(data []byte) error {
+	result, err := ParseInt(string(bytes.Trim(data, `"`)))
+	*i = hexInt(result)
+
+	return err
+}
+
+type hexBig big.Int
+
+func (i *hexBig) UnmarshalJSON(data []byte) error {
+	result, err := ParseBigInt(string(bytes.Trim(data, `"`)))
+	*i = hexBig(result)
+
+	return err
+}
+
+type proxyBlock interface {
+	toBlock() Block
+}
+
+type proxyBlockWithTransactions struct {
+	Number           hexInt             `json:"number"`
+	Hash             string             `json:"hash"`
+	ParentHash       string             `json:"parentHash"`
+	Nonce            string             `json:"nonce"`
+	Sha3Uncles       string             `json:"sha3Uncles"`
+	LogsBloom        string             `json:"logsBloom"`
+	TransactionsRoot string             `json:"transactionsRoot"`
+	StateRoot        string             `json:"stateRoot"`
+	Miner            string             `json:"miner"`
+	Difficulty       hexBig             `json:"difficulty"`
+	TotalDifficulty  hexBig             `json:"totalDifficulty"`
+	ExtraData        string             `json:"extraData"`
+	Size             hexInt             `json:"size"`
+	GasLimit         hexInt             `json:"gasLimit"`
+	GasUsed          hexInt             `json:"gasUsed"`
+	Timestamp        hexInt             `json:"timestamp"`
+	Uncles           []string           `json:"uncles"`
+	Transactions     []proxyTransaction `json:"transactions"`
+}
+
+func (proxy *proxyBlockWithTransactions) toBlock() Block {
+	return *(*Block)(unsafe.Pointer(proxy))
+}
+
+type proxyBlockWithoutTransactions struct {
+	Number           hexInt   `json:"number"`
+	Hash             string   `json:"hash"`
+	ParentHash       string   `json:"parentHash"`
+	Nonce            string   `json:"nonce"`
+	Sha3Uncles       string   `json:"sha3Uncles"`
+	LogsBloom        string   `json:"logsBloom"`
+	TransactionsRoot string   `json:"transactionsRoot"`
+	StateRoot        string   `json:"stateRoot"`
+	Miner            string   `json:"miner"`
+	Difficulty       hexBig   `json:"difficulty"`
+	TotalDifficulty  hexBig   `json:"totalDifficulty"`
+	ExtraData        string   `json:"extraData"`
+	Size             hexInt   `json:"size"`
+	GasLimit         hexInt   `json:"gasLimit"`
+	GasUsed          hexInt   `json:"gasUsed"`
+	Timestamp        hexInt   `json:"timestamp"`
+	Uncles           []string `json:"uncles"`
+	Transactions     []string `json:"transactions"`
+}
+
+func (proxy *proxyBlockWithoutTransactions) toBlock() Block {
+	block := Block{
+		Number:           int(proxy.Number),
+		Hash:             proxy.Hash,
+		ParentHash:       proxy.ParentHash,
+		Nonce:            proxy.Nonce,
+		Sha3Uncles:       proxy.Sha3Uncles,
+		LogsBloom:        proxy.LogsBloom,
+		TransactionsRoot: proxy.TransactionsRoot,
+		StateRoot:        proxy.StateRoot,
+		Miner:            proxy.Miner,
+		Difficulty:       big.Int(proxy.Difficulty),
+		TotalDifficulty:  big.Int(proxy.TotalDifficulty),
+		ExtraData:        proxy.ExtraData,
+		Size:             int(proxy.Size),
+		GasLimit:         int(proxy.GasLimit),
+		GasUsed:          int(proxy.GasUsed),
+		Timestamp:        int(proxy.Timestamp),
+		Uncles:           proxy.Uncles,
+	}
+
+	block.Transactions = make([]Transaction, len(proxy.Transactions))
+	for i := range proxy.Transactions {
+		block.Transactions[i] = Transaction{
+			Hash: proxy.Transactions[i],
+		}
+	}
+
+	return block
+}
diff --git a/vendor/vendor.json b/vendor/vendor.json
index 12978a6cd..aa7a3ff65 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -141,16 +141,16 @@
 		{
 			"checksumSHA1": "8EuKVkP1v/w5fRuuvUaXX5k/F+I=",
 			"path": "github.com/dexon-foundation/dexon-consensus/common",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
-			"checksumSHA1": "ukcaBY+jnQSKyanW+y/uwysV+VM=",
+			"checksumSHA1": "bYtL3br8SNzJRQzD0leNywoSo2M=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
@@ -165,64 +165,64 @@
 		{
 			"checksumSHA1": "tQSbYCu5P00lUhKsx3IbBZCuSLY=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/crypto",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
 			"checksumSHA1": "kC/Tu4is9+jABI/EdvEv7VxwvEo=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/crypto/dkg",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
 			"checksumSHA1": "BhLKK8RveoLaeXc9UyUKMwQqchU=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/crypto/ecdsa",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
 			"checksumSHA1": "dQOZYmiikmjWhwkUJc0QmCJnO9o=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/db",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
-			"checksumSHA1": "wN+K5gI8+j/7l3SB0DYZ8MkTAwo=",
+			"checksumSHA1": "H0+GIDijBmoic/0HSTZBUwEij5A=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/syncer",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
 			"checksumSHA1": "id8imcgp3SqYhIx0k3Chd0VZrUQ=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/types",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
 			"checksumSHA1": "QXRBX9UmvX4wszA9qlyJtzYcTOw=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/types/dkg",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
 		{
-			"checksumSHA1": "Hg7KG7RnXK3Autq05xDxSIHKxXI=",
+			"checksumSHA1": "D9I012bShlJM+rsYxG5sH5nvqXA=",
 			"path": "github.com/dexon-foundation/dexon-consensus/core/utils",
-			"revision": "8786160e28cf17c1125e26939b81ac59df5c260a",
-			"revisionTime": "2019-03-13T07:38:33Z",
+			"revision": "c0e1c45539fe882c4cd096a41e36f764d5ad2092",
+			"revisionTime": "2019-03-16T10:51:30Z",
 			"version": "single-chain",
 			"versionExact": "single-chain"
 		},
@@ -517,6 +517,12 @@
 			"revisionTime": "2017-01-28T05:05:32Z"
 		},
 		{
+			"checksumSHA1": "VxE5yTGoSXiesg2xRPo0lomflF0=",
+			"path": "github.com/onrik/ethrpc",
+			"revision": "6b8e9c0e9a8ffd2154cd4470a6ffb4919885e788",
+			"revisionTime": "2019-03-05T11:28:07Z"
+		},
+		{
 			"checksumSHA1": "wIcN7tZiF441h08RHAm4NV8cYO4=",
 			"path": "github.com/opentracing/opentracing-go",
 			"revision": "bd9c3193394760d98b2fa6ebb2291f0cd1d06a7d",