accounts: refactor API for generalized USB wallets

13 files changed, 1450 insertions, 1965 deletions

diff --git a/accounts/accounts.go b/accounts/accounts.go
index 5872bb4a3..76951e1a4 100644
--- a/accounts/accounts.go
+++ b/accounts/accounts.go
@@ -42,8 +42,9 @@ type Wallet interface {
 	URL() URL
 
 	// Status returns a textual status to aid the user in the current state of the
-	// wallet.
-	Status() string
+	// wallet. It also returns an error indicating any failure the wallet might have
+	// encountered.
+	Status() (string, error)
 
 	// Open initializes access to a wallet instance. It is not meant to unlock or
 	// decrypt account keys, rather simply to establish a connection to hardware
diff --git a/accounts/hd_test.go b/accounts/hd_test.go
index 83ec34adb..b6b23230d 100644
--- a/accounts/hd_test.go
+++ b/accounts/hd_test.go
@@ -37,11 +37,11 @@ func TestHDPathParsing(t *testing.T) {
 		{"m/2147483692/2147483708/2147483648/2147483648", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
 
 		// Plain relative derivation paths
-		{"0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
-		{"128", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
-		{"0'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
-		{"128'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
-		{"2147483648", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0}},
+		{"128", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 128}},
+		{"0'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 0}},
+		{"128'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 128}},
+		{"2147483648", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 0}},
 
 		// Hexadecimal absolute derivation paths
 		{"m/0x2C'/0x3c'/0x00'/0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
@@ -52,11 +52,11 @@ func TestHDPathParsing(t *testing.T) {
 		{"m/0x8000002C/0x8000003c/0x80000000/0x80000000", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
 
 		// Hexadecimal relative derivation paths
-		{"0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
-		{"0x80", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
-		{"0x00'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
-		{"0x80'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
-		{"0x80000000", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0}},
+		{"0x80", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 128}},
+		{"0x00'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 0}},
+		{"0x80'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 128}},
+		{"0x80000000", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0, 0x80000000 + 0}},
 
 		// Weird inputs just to ensure they work
 		{"	m  /   44			'\n/\n   60	\n\n\t'   /\n0 ' /\t\t	0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
diff --git a/accounts/keystore/keystore_wallet.go b/accounts/keystore/keystore_wallet.go
index 7165d2821..758fdfe36 100644
--- a/accounts/keystore/keystore_wallet.go
+++ b/accounts/keystore/keystore_wallet.go
@@ -36,16 +36,16 @@ func (w *keystoreWallet) URL() accounts.URL {
 	return w.account.URL
 }
 
-// Status implements accounts.Wallet, always returning "open", since there is no
-// concept of open/close for plain keystore accounts.
-func (w *keystoreWallet) Status() string {
+// Status implements accounts.Wallet, returning whether the account held by the
+// keystore wallet is unlocked or not.
+func (w *keystoreWallet) Status() (string, error) {
 	w.keystore.mu.RLock()
 	defer w.keystore.mu.RUnlock()
 
 	if _, ok := w.keystore.unlocked[w.account.Address]; ok {
-		return "Unlocked"
+		return "Unlocked", nil
 	}
-	return "Locked"
+	return "Locked", nil
 }
 
 // Open implements accounts.Wallet, but is a noop for plain wallets since there
diff --git a/accounts/usbwallet/ledger_hub.go b/accounts/usbwallet/hub.go
index ffe7cffe4..7069d2531 100644
--- a/accounts/usbwallet/ledger_hub.go
+++ b/accounts/usbwallet/hub.go
@@ -29,24 +29,28 @@ import (
 )
 
 // LedgerScheme is the protocol scheme prefixing account and wallet URLs.
-var LedgerScheme = "ledger"
+const LedgerScheme = "ledger"
 
-// ledgerDeviceIDs are the known device IDs that Ledger wallets use.
-var ledgerDeviceIDs = []deviceID{
-	{Vendor: 0x2c97, Product: 0x0000}, // Ledger Blue
-	{Vendor: 0x2c97, Product: 0x0001}, // Ledger Nano S
-}
+// TrezorScheme is the protocol scheme prefixing account and wallet URLs.
+const TrezorScheme = "trezor"
+
+// refreshCycle is the maximum time between wallet refreshes (if USB hotplug
+// notifications don't work).
+const refreshCycle = time.Second
 
-// Maximum time between wallet refreshes (if USB hotplug notifications don't work).
-const ledgerRefreshCycle = time.Second
+// refreshThrottling is the minimum time between wallet refreshes to avoid USB
+// trashing.
+const refreshThrottling = 500 * time.Millisecond
 
-// Minimum time between wallet refreshes to avoid USB trashing.
-const ledgerRefreshThrottling = 500 * time.Millisecond
+// Hub is a accounts.Backend that can find and handle generic USB hardware wallets.
+type Hub struct {
+	scheme     string                  // Protocol scheme prefixing account and wallet URLs.
+	vendorID   uint16                  // USB vendor identifier used for device discovery
+	productIDs []uint16                // USB product identifiers used for device discovery
+	makeDriver func(log.Logger) driver // Factory method to construct a vendor specific driver
 
-// LedgerHub is a accounts.Backend that can find and handle Ledger hardware wallets.
-type LedgerHub struct {
 	refreshed   time.Time               // Time instance when the list of wallets was last refreshed
-	wallets     []accounts.Wallet       // List of Ledger devices currently tracking
+	wallets     []accounts.Wallet       // List of USB wallet devices currently tracking
 	updateFeed  event.Feed              // Event feed to notify wallet additions/removals
 	updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
 	updating    bool                    // Whether the event notification loop is running
@@ -61,20 +65,34 @@ type LedgerHub struct {
 }
 
 // NewLedgerHub creates a new hardware wallet manager for Ledger devices.
-func NewLedgerHub() (*LedgerHub, error) {
+func NewLedgerHub() (*Hub, error) {
+	return newHub(LedgerScheme, 0x2c97, []uint16{0x0000 /* Ledger Blue */, 0x0001 /* Ledger Nano S */}, newLedgerDriver)
+}
+
+// NewTrezorHub creates a new hardware wallet manager for Trezor devices.
+func NewTrezorHub() (*Hub, error) {
+	return newHub(TrezorScheme, 0x534c, []uint16{0x0001 /* Trezor 1 */}, newTrezorDriver)
+}
+
+// newHub creates a new hardware wallet manager for generic USB devices.
+func newHub(scheme string, vendorID uint16, productIDs []uint16, makeDriver func(log.Logger) driver) (*Hub, error) {
 	if !hid.Supported() {
 		return nil, errors.New("unsupported platform")
 	}
-	hub := &LedgerHub{
-		quit: make(chan chan error),
+	hub := &Hub{
+		scheme:     scheme,
+		vendorID:   vendorID,
+		productIDs: productIDs,
+		makeDriver: makeDriver,
+		quit:       make(chan chan error),
 	}
 	hub.refreshWallets()
 	return hub, nil
 }
 
 // Wallets implements accounts.Backend, returning all the currently tracked USB
-// devices that appear to be Ledger hardware wallets.
-func (hub *LedgerHub) Wallets() []accounts.Wallet {
+// devices that appear to be hardware wallets.
+func (hub *Hub) Wallets() []accounts.Wallet {
 	// Make sure the list of wallets is up to date
 	hub.refreshWallets()
 
@@ -88,17 +106,17 @@ func (hub *LedgerHub) Wallets() []accounts.Wallet {
 
 // refreshWallets scans the USB devices attached to the machine and updates the
 // list of wallets based on the found devices.
-func (hub *LedgerHub) refreshWallets() {
+func (hub *Hub) refreshWallets() {
 	// Don't scan the USB like crazy it the user fetches wallets in a loop
 	hub.stateLock.RLock()
 	elapsed := time.Since(hub.refreshed)
 	hub.stateLock.RUnlock()
 
-	if elapsed < ledgerRefreshThrottling {
+	if elapsed < refreshThrottling {
 		return
 	}
-	// Retrieve the current list of Ledger devices
-	var ledgers []hid.DeviceInfo
+	// Retrieve the current list of USB wallet devices
+	var devices []hid.DeviceInfo
 
 	if runtime.GOOS == "linux" {
 		// hidapi on Linux opens the device during enumeration to retrieve some infos,
@@ -113,10 +131,10 @@ func (hub *LedgerHub) refreshWallets() {
 			return
 		}
 	}
-	for _, info := range hid.Enumerate(0, 0) { // Can't enumerate directly, one valid ID is the 0 wildcard
-		for _, id := range ledgerDeviceIDs {
-			if info.VendorID == id.Vendor && info.ProductID == id.Product {
-				ledgers = append(ledgers, info)
+	for _, info := range hid.Enumerate(hub.vendorID, 0) {
+		for _, id := range hub.productIDs {
+			if info.ProductID == id && info.Interface == 0 {
+				devices = append(devices, info)
 				break
 			}
 		}
@@ -128,20 +146,27 @@ func (hub *LedgerHub) refreshWallets() {
 	// Transform the current list of wallets into the new one
 	hub.stateLock.Lock()
 
-	wallets := make([]accounts.Wallet, 0, len(ledgers))
+	wallets := make([]accounts.Wallet, 0, len(devices))
 	events := []accounts.WalletEvent{}
 
-	for _, ledger := range ledgers {
-		url := accounts.URL{Scheme: LedgerScheme, Path: ledger.Path}
+	for _, device := range devices {
+		url := accounts.URL{Scheme: hub.scheme, Path: device.Path}
 
 		// Drop wallets in front of the next device or those that failed for some reason
-		for len(hub.wallets) > 0 && (hub.wallets[0].URL().Cmp(url) < 0 || hub.wallets[0].(*ledgerWallet).failed()) {
+		for len(hub.wallets) > 0 {
+			// Abort if we're past the current device and found an operational one
+			_, failure := hub.wallets[0].Status()
+			if hub.wallets[0].URL().Cmp(url) >= 0 || failure == nil {
+				break
+			}
+			// Drop the stale and failed devices
 			events = append(events, accounts.WalletEvent{Wallet: hub.wallets[0], Kind: accounts.WalletDropped})
 			hub.wallets = hub.wallets[1:]
 		}
 		// If there are no more wallets or the device is before the next, wrap new wallet
 		if len(hub.wallets) == 0 || hub.wallets[0].URL().Cmp(url) > 0 {
-			wallet := &ledgerWallet{hub: hub, url: &url, info: ledger, log: log.New("url", url)}
+			logger := log.New("url", url)
+			wallet := &wallet{hub: hub, driver: hub.makeDriver(logger), url: &url, info: device, log: logger}
 
 			events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletArrived})
 			wallets = append(wallets, wallet)
@@ -169,8 +194,8 @@ func (hub *LedgerHub) refreshWallets() {
 }
 
 // Subscribe implements accounts.Backend, creating an async subscription to
-// receive notifications on the addition or removal of Ledger wallets.
-func (hub *LedgerHub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
+// receive notifications on the addition or removal of USB wallets.
+func (hub *Hub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
 	// We need the mutex to reliably start/stop the update loop
 	hub.stateLock.Lock()
 	defer hub.stateLock.Unlock()
@@ -186,16 +211,13 @@ func (hub *LedgerHub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscrip
 	return sub
 }
 
-// updater is responsible for maintaining an up-to-date list of wallets stored in
-// the keystore, and for firing wallet addition/removal events. It listens for
-// account change events from the underlying account cache, and also periodically
-// forces a manual refresh (only triggers for systems where the filesystem notifier
-// is not running).
-func (hub *LedgerHub) updater() {
+// updater is responsible for maintaining an up-to-date list of wallets managed
+// by the USB hub, and for firing wallet addition/removal events.
+func (hub *Hub) updater() {
 	for {
 		// TODO: Wait for a USB hotplug event (not supported yet) or a refresh timeout
 		// <-hub.changes
-		time.Sleep(ledgerRefreshCycle)
+		time.Sleep(refreshCycle)
 
 		// Run the wallet refresher
 		hub.refreshWallets()
diff --git a/accounts/usbwallet/ledger.go b/accounts/usbwallet/ledger.go
new file mode 100644
index 000000000..f5def61d2
--- /dev/null
+++ b/accounts/usbwallet/ledger.go
@@ -0,0 +1,464 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// This file contains the implementation for interacting with the Ledger hardware
+// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
+// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
+
+package usbwallet
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// ledgerOpcode is an enumeration encoding the supported Ledger opcodes.
+type ledgerOpcode byte
+
+// ledgerParam1 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam1 byte
+
+// ledgerParam2 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam2 byte
+
+const (
+	ledgerOpRetrieveAddress  ledgerOpcode = 0x02 // Returns the public key and Ethereum address for a given BIP 32 path
+	ledgerOpSignTransaction  ledgerOpcode = 0x04 // Signs an Ethereum transaction after having the user validate the parameters
+	ledgerOpGetConfiguration ledgerOpcode = 0x06 // Returns specific wallet application configuration
+
+	ledgerP1DirectlyFetchAddress    ledgerParam1 = 0x00 // Return address directly from the wallet
+	ledgerP1ConfirmFetchAddress     ledgerParam1 = 0x01 // Require a user confirmation before returning the address
+	ledgerP1InitTransactionData     ledgerParam1 = 0x00 // First transaction data block for signing
+	ledgerP1ContTransactionData     ledgerParam1 = 0x80 // Subsequent transaction data block for signing
+	ledgerP2DiscardAddressChainCode ledgerParam2 = 0x00 // Do not return the chain code along with the address
+	ledgerP2ReturnAddressChainCode  ledgerParam2 = 0x01 // Require a user confirmation before returning the address
+)
+
+// errLedgerReplyInvalidHeader is the error message returned by a Ledger data exchange
+// if the device replies with a mismatching header. This usually means the device
+// is in browser mode.
+var errLedgerReplyInvalidHeader = errors.New("ledger: invalid reply header")
+
+// errLedgerInvalidVersionReply is the error message returned by a Ledger version retrieval
+// when a response does arrive, but it does not contain the expected data.
+var errLedgerInvalidVersionReply = errors.New("ledger: invalid version reply")
+
+// ledgerDriver implements the communication with a Ledger hardware wallet.
+type ledgerDriver struct {
+	device  io.ReadWriter // USB device connection to communicate through
+	version [3]byte       // Current version of the Ledger firmware (zero if app is offline)
+	browser bool          // Flag whether the Ledger is in browser mode (reply channel mismatch)
+	failure error         // Any failure that would make the device unusable
+	log     log.Logger    // Contextual logger to tag the ledger with its id
+}
+
+// newLedgerDriver creates a new instance of a Ledger USB protocol driver.
+func newLedgerDriver(logger log.Logger) driver {
+	return &ledgerDriver{
+		log: logger,
+	}
+}
+
+// Status implements usbwallet.driver, returning various states the Ledger can
+// currently be in.
+func (w *ledgerDriver) Status() (string, error) {
+	if w.failure != nil {
+		return fmt.Sprintf("Failed: %v", w.failure), w.failure
+	}
+	if w.browser {
+		return "Ethereum app in browser mode", w.failure
+	}
+	if w.offline() {
+		return "Ethereum app offline", w.failure
+	}
+	return fmt.Sprintf("Ethereum app v%d.%d.%d online", w.version[0], w.version[1], w.version[2]), w.failure
+}
+
+// offline returns whether the wallet and the Ethereum app is offline or not.
+//
+// The method assumes that the state lock is held!
+func (w *ledgerDriver) offline() bool {
+	return w.version == [3]byte{0, 0, 0}
+}
+
+// Open implements usbwallet.driver, attempting to initialize the connection to the
+// Ledger hardware wallet. The Ledger does not require a user passphrase, so that
+// parameter is silently discarded.
+func (w *ledgerDriver) Open(device io.ReadWriter, passphrase string) error {
+	w.device, w.failure = device, nil
+
+	_, err := w.ledgerDerive(accounts.DefaultBaseDerivationPath)
+	if err != nil {
+		// Ethereum app is not running or in browser mode, nothing more to do, return
+		if err == errLedgerReplyInvalidHeader {
+			w.browser = true
+		}
+		return nil
+	}
+	// Try to resolve the Ethereum app's version, will fail prior to v1.0.2
+	if w.version, err = w.ledgerVersion(); err != nil {
+		w.version = [3]byte{1, 0, 0} // Assume worst case, can't verify if v1.0.0 or v1.0.1
+	}
+	return nil
+}
+
+// Close implements usbwallet.driver, cleaning up and metadata maintained within
+// the Ledger driver.
+func (w *ledgerDriver) Close() error {
+	w.browser, w.version = false, [3]byte{}
+	return nil
+}
+
+// Heartbeat implements usbwallet.driver, performing a sanity check against the
+// Ledger to see if it's still online.
+func (w *ledgerDriver) Heartbeat() error {
+	if _, err := w.ledgerVersion(); err != nil && err != errLedgerInvalidVersionReply {
+		w.failure = err
+		return err
+	}
+	return nil
+}
+
+// Derive implements usbwallet.driver, sending a derivation request to the Ledger
+// and returning the Ethereum address located on that derivation path.
+func (w *ledgerDriver) Derive(path accounts.DerivationPath) (common.Address, error) {
+	return w.ledgerDerive(path)
+}
+
+// SignTx implements usbwallet.driver, sending the transaction to the Ledger and
+// waiting for the user to confirm or deny the transaction.
+//
+// Note, if the version of the Ethereum application running on the Ledger wallet is
+// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
+// will be returned opposed to silently signing in Homestead mode.
+func (w *ledgerDriver) SignTx(path accounts.DerivationPath, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
+	// If the Ethereum app doesn't run, abort
+	if w.offline() {
+		return common.Address{}, nil, accounts.ErrWalletClosed
+	}
+	// Ensure the wallet is capable of signing the given transaction
+	if chainID != nil && w.version[0] <= 1 && w.version[1] <= 0 && w.version[2] <= 2 {
+		return common.Address{}, nil, fmt.Errorf("Ledger v%d.%d.%d doesn't support signing this transaction, please update to v1.0.3 at least", w.version[0], w.version[1], w.version[2])
+	}
+	// All infos gathered and metadata checks out, request signing
+	return w.ledgerSign(path, tx, chainID)
+}
+
+// ledgerVersion retrieves the current version of the Ethereum wallet app running
+// on the Ledger wallet.
+//
+// The version retrieval protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc | Le
+//   ----+-----+----+----+----+---
+//    E0 | 06  | 00 | 00 | 00 | 04
+//
+// With no input data, and the output data being:
+//
+//   Description                                        | Length
+//   ---------------------------------------------------+--------
+//   Flags 01: arbitrary data signature enabled by user | 1 byte
+//   Application major version                          | 1 byte
+//   Application minor version                          | 1 byte
+//   Application patch version                          | 1 byte
+func (w *ledgerDriver) ledgerVersion() ([3]byte, error) {
+	// Send the request and wait for the response
+	reply, err := w.ledgerExchange(ledgerOpGetConfiguration, 0, 0, nil)
+	if err != nil {
+		return [3]byte{}, err
+	}
+	if len(reply) != 4 {
+		return [3]byte{}, errLedgerInvalidVersionReply
+	}
+	// Cache the version for future reference
+	var version [3]byte
+	copy(version[:], reply[1:])
+	return version, nil
+}
+
+// ledgerDerive retrieves the currently active Ethereum address from a Ledger
+// wallet at the specified derivation path.
+//
+// The address derivation protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 02  | 00 return address
+//               01 display address and confirm before returning
+//                  | 00: do not return the chain code
+//                  | 01: return the chain code
+//                       | var | 00
+//
+// Where the input data is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+--------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//
+// And the output data is:
+//
+//   Description             | Length
+//   ------------------------+-------------------
+//   Public Key length       | 1 byte
+//   Uncompressed Public Key | arbitrary
+//   Ethereum address length | 1 byte
+//   Ethereum address        | 40 bytes hex ascii
+//   Chain code if requested | 32 bytes
+func (w *ledgerDriver) ledgerDerive(derivationPath []uint32) (common.Address, error) {
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(derivationPath))
+	path[0] = byte(len(derivationPath))
+	for i, component := range derivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Send the request and wait for the response
+	reply, err := w.ledgerExchange(ledgerOpRetrieveAddress, ledgerP1DirectlyFetchAddress, ledgerP2DiscardAddressChainCode, path)
+	if err != nil {
+		return common.Address{}, err
+	}
+	// Discard the public key, we don't need that for now
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return common.Address{}, errors.New("reply lacks public key entry")
+	}
+	reply = reply[1+int(reply[0]):]
+
+	// Extract the Ethereum hex address string
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return common.Address{}, errors.New("reply lacks address entry")
+	}
+	hexstr := reply[1 : 1+int(reply[0])]
+
+	// Decode the hex sting into an Ethereum address and return
+	var address common.Address
+	hex.Decode(address[:], hexstr)
+	return address, nil
+}
+
+// ledgerSign sends the transaction to the Ledger wallet, and waits for the user
+// to confirm or deny the transaction.
+//
+// The transaction signing protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 04  | 00: first transaction data block
+//               80: subsequent transaction data block
+//                  | 00 | variable | variable
+//
+// Where the input for the first transaction block (first 255 bytes) is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+----------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//   RLP transaction chunk                            | arbitrary
+//
+// And the input for subsequent transaction blocks (first 255 bytes) are:
+//
+//   Description           | Length
+//   ----------------------+----------
+//   RLP transaction chunk | arbitrary
+//
+// And the output data is:
+//
+//   Description | Length
+//   ------------+---------
+//   signature V | 1 byte
+//   signature R | 32 bytes
+//   signature S | 32 bytes
+func (w *ledgerDriver) ledgerSign(derivationPath []uint32, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(derivationPath))
+	path[0] = byte(len(derivationPath))
+	for i, component := range derivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Create the transaction RLP based on whether legacy or EIP155 signing was requeste
+	var (
+		txrlp []byte
+		err   error
+	)
+	if chainID == nil {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data()}); err != nil {
+			return common.Address{}, nil, err
+		}
+	} else {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data(), chainID, big.NewInt(0), big.NewInt(0)}); err != nil {
+			return common.Address{}, nil, err
+		}
+	}
+	payload := append(path, txrlp...)
+
+	// Send the request and wait for the response
+	var (
+		op    = ledgerP1InitTransactionData
+		reply []byte
+	)
+	for len(payload) > 0 {
+		// Calculate the size of the next data chunk
+		chunk := 255
+		if chunk > len(payload) {
+			chunk = len(payload)
+		}
+		// Send the chunk over, ensuring it's processed correctly
+		reply, err = w.ledgerExchange(ledgerOpSignTransaction, op, 0, payload[:chunk])
+		if err != nil {
+			return common.Address{}, nil, err
+		}
+		// Shift the payload and ensure subsequent chunks are marked as such
+		payload = payload[chunk:]
+		op = ledgerP1ContTransactionData
+	}
+	// Extract the Ethereum signature and do a sanity validation
+	if len(reply) != 65 {
+		return common.Address{}, nil, errors.New("reply lacks signature")
+	}
+	signature := append(reply[1:], reply[0])
+
+	// Create the correct signer and signature transform based on the chain ID
+	var signer types.Signer
+	if chainID == nil {
+		signer = new(types.HomesteadSigner)
+	} else {
+		signer = types.NewEIP155Signer(chainID)
+		signature[64] = signature[64] - byte(chainID.Uint64()*2+35)
+	}
+	signed, err := tx.WithSignature(signer, signature)
+	if err != nil {
+		return common.Address{}, nil, err
+	}
+	sender, err := types.Sender(signer, signed)
+	if err != nil {
+		return common.Address{}, nil, err
+	}
+	return sender, signed, nil
+}
+
+// ledgerExchange performs a data exchange with the Ledger wallet, sending it a
+// message and retrieving the response.
+//
+// The common transport header is defined as follows:
+//
+//  Description                           | Length
+//  --------------------------------------+----------
+//  Communication channel ID (big endian) | 2 bytes
+//  Command tag                           | 1 byte
+//  Packet sequence index (big endian)    | 2 bytes
+//  Payload                               | arbitrary
+//
+// The Communication channel ID allows commands multiplexing over the same
+// physical link. It is not used for the time being, and should be set to 0101
+// to avoid compatibility issues with implementations ignoring a leading 00 byte.
+//
+// The Command tag describes the message content. Use TAG_APDU (0x05) for standard
+// APDU payloads, or TAG_PING (0x02) for a simple link test.
+//
+// The Packet sequence index describes the current sequence for fragmented payloads.
+// The first fragment index is 0x00.
+//
+// APDU Command payloads are encoded as follows:
+//
+//  Description              | Length
+//  -----------------------------------
+//  APDU length (big endian) | 2 bytes
+//  APDU CLA                 | 1 byte
+//  APDU INS                 | 1 byte
+//  APDU P1                  | 1 byte
+//  APDU P2                  | 1 byte
+//  APDU length              | 1 byte
+//  Optional APDU data       | arbitrary
+func (w *ledgerDriver) ledgerExchange(opcode ledgerOpcode, p1 ledgerParam1, p2 ledgerParam2, data []byte) ([]byte, error) {
+	// Construct the message payload, possibly split into multiple chunks
+	apdu := make([]byte, 2, 7+len(data))
+
+	binary.BigEndian.PutUint16(apdu, uint16(5+len(data)))
+	apdu = append(apdu, []byte{0xe0, byte(opcode), byte(p1), byte(p2), byte(len(data))}...)
+	apdu = append(apdu, data...)
+
+	// Stream all the chunks to the device
+	header := []byte{0x01, 0x01, 0x05, 0x00, 0x00} // Channel ID and command tag appended
+	chunk := make([]byte, 64)
+	space := len(chunk) - len(header)
+
+	for i := 0; len(apdu) > 0; i++ {
+		// Construct the new message to stream
+		chunk = append(chunk[:0], header...)
+		binary.BigEndian.PutUint16(chunk[3:], uint16(i))
+
+		if len(apdu) > space {
+			chunk = append(chunk, apdu[:space]...)
+			apdu = apdu[space:]
+		} else {
+			chunk = append(chunk, apdu...)
+			apdu = nil
+		}
+		// Send over to the device
+		w.log.Trace("Data chunk sent to the Ledger", "chunk", hexutil.Bytes(chunk))
+		if _, err := w.device.Write(chunk); err != nil {
+			return nil, err
+		}
+	}
+	// Stream the reply back from the wallet in 64 byte chunks
+	var reply []byte
+	chunk = chunk[:64] // Yeah, we surely have enough space
+	for {
+		// Read the next chunk from the Ledger wallet
+		if _, err := io.ReadFull(w.device, chunk); err != nil {
+			return nil, err
+		}
+		w.log.Trace("Data chunk received from the Ledger", "chunk", hexutil.Bytes(chunk))
+
+		// Make sure the transport header matches
+		if chunk[0] != 0x01 || chunk[1] != 0x01 || chunk[2] != 0x05 {
+			return nil, errLedgerReplyInvalidHeader
+		}
+		// If it's the first chunk, retrieve the total message length
+		var payload []byte
+
+		if chunk[3] == 0x00 && chunk[4] == 0x00 {
+			reply = make([]byte, 0, int(binary.BigEndian.Uint16(chunk[5:7])))
+			payload = chunk[7:]
+		} else {
+			payload = chunk[5:]
+		}
+		// Append to the reply and stop when filled up
+		if left := cap(reply) - len(reply); left > len(payload) {
+			reply = append(reply, payload...)
+		} else {
+			reply = append(reply, payload[:left]...)
+			break
+		}
+	}
+	return reply[:len(reply)-2], nil
+}
diff --git a/accounts/usbwallet/ledger_wallet.go b/accounts/usbwallet/ledger_wallet.go
deleted file mode 100644
index b8f04d74c..000000000
--- a/accounts/usbwallet/ledger_wallet.go
+++ /dev/null
@@ -1,898 +0,0 @@
-// Copyright 2017 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-// This file contains the implementation for interacting with the Ledger hardware
-// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
-// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
-
-package usbwallet
-
-import (
-	"context"
-	"encoding/binary"
-	"encoding/hex"
-	"errors"
-	"fmt"
-	"io"
-	"math/big"
-	"sync"
-	"time"
-
-	ethereum "github.com/ethereum/go-ethereum"
-	"github.com/ethereum/go-ethereum/accounts"
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/hexutil"
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/rlp"
-	"github.com/karalabe/hid"
-)
-
-// ledgerOpcode is an enumeration encoding the supported Ledger opcodes.
-type ledgerOpcode byte
-
-// ledgerParam1 is an enumeration encoding the supported Ledger parameters for
-// specific opcodes. The same parameter values may be reused between opcodes.
-type ledgerParam1 byte
-
-// ledgerParam2 is an enumeration encoding the supported Ledger parameters for
-// specific opcodes. The same parameter values may be reused between opcodes.
-type ledgerParam2 byte
-
-const (
-	ledgerOpRetrieveAddress  ledgerOpcode = 0x02 // Returns the public key and Ethereum address for a given BIP 32 path
-	ledgerOpSignTransaction  ledgerOpcode = 0x04 // Signs an Ethereum transaction after having the user validate the parameters
-	ledgerOpGetConfiguration ledgerOpcode = 0x06 // Returns specific wallet application configuration
-
-	ledgerP1DirectlyFetchAddress    ledgerParam1 = 0x00 // Return address directly from the wallet
-	ledgerP1ConfirmFetchAddress     ledgerParam1 = 0x01 // Require a user confirmation before returning the address
-	ledgerP1InitTransactionData     ledgerParam1 = 0x00 // First transaction data block for signing
-	ledgerP1ContTransactionData     ledgerParam1 = 0x80 // Subsequent transaction data block for signing
-	ledgerP2DiscardAddressChainCode ledgerParam2 = 0x00 // Do not return the chain code along with the address
-	ledgerP2ReturnAddressChainCode  ledgerParam2 = 0x01 // Require a user confirmation before returning the address
-)
-
-// errReplyInvalidHeader is the error message returned by a Ledger data exchange
-// if the device replies with a mismatching header. This usually means the device
-// is in browser mode.
-var errReplyInvalidHeader = errors.New("invalid reply header")
-
-// errInvalidVersionReply is the error message returned by a Ledger version retrieval
-// when a response does arrive, but it does not contain the expected data.
-var errInvalidVersionReply = errors.New("invalid version reply")
-
-// ledgerWallet represents a live USB Ledger hardware wallet.
-type ledgerWallet struct {
-	hub *LedgerHub    // USB hub the device originates from (TODO(karalabe): remove if hotplug lands on Windows)
-	url *accounts.URL // Textual URL uniquely identifying this wallet
-
-	info    hid.DeviceInfo // Known USB device infos about the wallet
-	device  *hid.Device    // USB device advertising itself as a Ledger wallet
-	failure error          // Any failure that would make the device unusable
-
-	version  [3]byte                                    // Current version of the Ledger Ethereum app (zero if app is offline)
-	browser  bool                                       // Flag whether the Ledger is in browser mode (reply channel mismatch)
-	accounts []accounts.Account                         // List of derive accounts pinned on the Ledger
-	paths    map[common.Address]accounts.DerivationPath // Known derivation paths for signing operations
-
-	deriveNextPath accounts.DerivationPath   // Next derivation path for account auto-discovery
-	deriveNextAddr common.Address            // Next derived account address for auto-discovery
-	deriveChain    ethereum.ChainStateReader // Blockchain state reader to discover used account with
-	deriveReq      chan chan struct{}        // Channel to request a self-derivation on
-	deriveQuit     chan chan error           // Channel to terminate the self-deriver with
-
-	healthQuit chan chan error
-
-	// Locking a hardware wallet is a bit special. Since hardware devices are lower
-	// performing, any communication with them might take a non negligible amount of
-	// time. Worse still, waiting for user confirmation can take arbitrarily long,
-	// but exclusive communication must be upheld during. Locking the entire wallet
-	// in the mean time however would stall any parts of the system that don't want
-	// to communicate, just read some state (e.g. list the accounts).
-	//
-	// As such, a hardware wallet needs two locks to function correctly. A state
-	// lock can be used to protect the wallet's software-side internal state, which
-	// must not be held exlusively during hardware communication. A communication
-	// lock can be used to achieve exclusive access to the device itself, this one
-	// however should allow "skipping" waiting for operations that might want to
-	// use the device, but can live without too (e.g. account self-derivation).
-	//
-	// Since we have two locks, it's important to know how to properly use them:
-	//   - Communication requires the `device` to not change, so obtaining the
-	//     commsLock should be done after having a stateLock.
-	//   - Communication must not disable read access to the wallet state, so it
-	//     must only ever hold a *read* lock to stateLock.
-	commsLock chan struct{} // Mutex (buf=1) for the USB comms without keeping the state locked
-	stateLock sync.RWMutex  // Protects read and write access to the wallet struct fields
-
-	log log.Logger // Contextual logger to tag the ledger with its id
-}
-
-// URL implements accounts.Wallet, returning the URL of the Ledger device.
-func (w *ledgerWallet) URL() accounts.URL {
-	return *w.url // Immutable, no need for a lock
-}
-
-// Status implements accounts.Wallet, always whether the Ledger is opened, closed
-// or whether the Ethereum app was not started on it.
-func (w *ledgerWallet) Status() string {
-	w.stateLock.RLock() // No device communication, state lock is enough
-	defer w.stateLock.RUnlock()
-
-	if w.failure != nil {
-		return fmt.Sprintf("Failed: %v", w.failure)
-	}
-	if w.device == nil {
-		return "Closed"
-	}
-	if w.browser {
-		return "Ethereum app in browser mode"
-	}
-	if w.offline() {
-		return "Ethereum app offline"
-	}
-	return fmt.Sprintf("Ethereum app v%d.%d.%d online", w.version[0], w.version[1], w.version[2])
-}
-
-// offline returns whether the wallet and the Ethereum app is offline or not.
-//
-// The method assumes that the state lock is held!
-func (w *ledgerWallet) offline() bool {
-	return w.version == [3]byte{0, 0, 0}
-}
-
-// failed returns if the USB device wrapped by the wallet failed for some reason.
-// This is used by the device scanner to report failed wallets as departed.
-//
-// The method assumes that the state lock is *not* held!
-func (w *ledgerWallet) failed() bool {
-	w.stateLock.RLock() // No device communication, state lock is enough
-	defer w.stateLock.RUnlock()
-
-	return w.failure != nil
-}
-
-// Open implements accounts.Wallet, attempting to open a USB connection to the
-// Ledger hardware wallet. The Ledger does not require a user passphrase, so that
-// parameter is silently discarded.
-func (w *ledgerWallet) Open(passphrase string) error {
-	w.stateLock.Lock() // State lock is enough since there's no connection yet at this point
-	defer w.stateLock.Unlock()
-
-	// If the wallet was already opened, don't try to open again
-	if w.device != nil {
-		return accounts.ErrWalletAlreadyOpen
-	}
-	// Otherwise iterate over all USB devices and find this again (no way to directly do this)
-	device, err := w.info.Open()
-	if err != nil {
-		return err
-	}
-	// Wallet seems to be successfully opened, guess if the Ethereum app is running
-	w.device = device
-	w.commsLock = make(chan struct{}, 1)
-	w.commsLock <- struct{}{} // Enable lock
-
-	w.paths = make(map[common.Address]accounts.DerivationPath)
-
-	w.deriveReq = make(chan chan struct{})
-	w.deriveQuit = make(chan chan error)
-	w.healthQuit = make(chan chan error)
-
-	defer func() {
-		go w.heartbeat()
-		go w.selfDerive()
-	}()
-
-	if _, err = w.ledgerDerive(accounts.DefaultBaseDerivationPath); err != nil {
-		// Ethereum app is not running or in browser mode, nothing more to do, return
-		if err == errReplyInvalidHeader {
-			w.browser = true
-		}
-		return nil
-	}
-	// Try to resolve the Ethereum app's version, will fail prior to v1.0.2
-	if w.version, err = w.ledgerVersion(); err != nil {
-		w.version = [3]byte{1, 0, 0} // Assume worst case, can't verify if v1.0.0 or v1.0.1
-	}
-	go w.hub.updateFeed.Send(accounts.WalletEvent{Wallet: w, Kind: accounts.WalletOpened})
-
-	return nil
-}
-
-// heartbeat is a health check loop for the Ledger wallets to periodically verify
-// whether they are still present or if they malfunctioned. It is needed because:
-//  - libusb on Windows doesn't support hotplug, so we can't detect USB unplugs
-//  - communication timeout on the Ledger requires a device power cycle to fix
-func (w *ledgerWallet) heartbeat() {
-	w.log.Debug("Ledger health-check started")
-	defer w.log.Debug("Ledger health-check stopped")
-
-	// Execute heartbeat checks until termination or error
-	var (
-		errc chan error
-		err  error
-	)
-	for errc == nil && err == nil {
-		// Wait until termination is requested or the heartbeat cycle arrives
-		select {
-		case errc = <-w.healthQuit:
-			// Termination requested
-			continue
-		case <-time.After(heartbeatCycle):
-			// Heartbeat time
-		}
-		// Execute a tiny data exchange to see responsiveness
-		w.stateLock.RLock()
-		if w.device == nil {
-			// Terminated while waiting for the lock
-			w.stateLock.RUnlock()
-			continue
-		}
-		<-w.commsLock // Don't lock state while resolving version
-		_, err = w.ledgerVersion()
-		w.commsLock <- struct{}{}
-		w.stateLock.RUnlock()
-
-		if err != nil && err != errInvalidVersionReply {
-			w.stateLock.Lock() // Lock state to tear the wallet down
-			w.failure = err
-			w.close()
-			w.stateLock.Unlock()
-		}
-		// Ignore non hardware related errors
-		err = nil
-	}
-	// In case of error, wait for termination
-	if err != nil {
-		w.log.Debug("Ledger health-check failed", "err", err)
-		errc = <-w.healthQuit
-	}
-	errc <- err
-}
-
-// Close implements accounts.Wallet, closing the USB connection to the Ledger.
-func (w *ledgerWallet) Close() error {
-	// Ensure the wallet was opened
-	w.stateLock.RLock()
-	hQuit, dQuit := w.healthQuit, w.deriveQuit
-	w.stateLock.RUnlock()
-
-	// Terminate the health checks
-	var herr error
-	if hQuit != nil {
-		errc := make(chan error)
-		hQuit <- errc
-		herr = <-errc // Save for later, we *must* close the USB
-	}
-	// Terminate the self-derivations
-	var derr error
-	if dQuit != nil {
-		errc := make(chan error)
-		dQuit <- errc
-		derr = <-errc // Save for later, we *must* close the USB
-	}
-	// Terminate the device connection
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	w.healthQuit = nil
-	w.deriveQuit = nil
-	w.deriveReq = nil
-
-	if err := w.close(); err != nil {
-		return err
-	}
-	if herr != nil {
-		return herr
-	}
-	return derr
-}
-
-// close is the internal wallet closer that terminates the USB connection and
-// resets all the fields to their defaults.
-//
-// Note, close assumes the state lock is held!
-func (w *ledgerWallet) close() error {
-	// Allow duplicate closes, especially for health-check failures
-	if w.device == nil {
-		return nil
-	}
-	// Close the device, clear everything, then return
-	w.device.Close()
-	w.device = nil
-
-	w.browser, w.version = false, [3]byte{}
-	w.accounts, w.paths = nil, nil
-
-	return nil
-}
-
-// Accounts implements accounts.Wallet, returning the list of accounts pinned to
-// the Ledger hardware wallet. If self-derivation was enabled, the account list
-// is periodically expanded based on current chain state.
-func (w *ledgerWallet) Accounts() []accounts.Account {
-	// Attempt self-derivation if it's running
-	reqc := make(chan struct{}, 1)
-	select {
-	case w.deriveReq <- reqc:
-		// Self-derivation request accepted, wait for it
-		<-reqc
-	default:
-		// Self-derivation offline, throttled or busy, skip
-	}
-	// Return whatever account list we ended up with
-	w.stateLock.RLock()
-	defer w.stateLock.RUnlock()
-
-	cpy := make([]accounts.Account, len(w.accounts))
-	copy(cpy, w.accounts)
-	return cpy
-}
-
-// selfDerive is an account derivation loop that upon request attempts to find
-// new non-zero accounts.
-func (w *ledgerWallet) selfDerive() {
-	w.log.Debug("Ledger self-derivation started")
-	defer w.log.Debug("Ledger self-derivation stopped")
-
-	// Execute self-derivations until termination or error
-	var (
-		reqc chan struct{}
-		errc chan error
-		err  error
-	)
-	for errc == nil && err == nil {
-		// Wait until either derivation or termination is requested
-		select {
-		case errc = <-w.deriveQuit:
-			// Termination requested
-			continue
-		case reqc = <-w.deriveReq:
-			// Account discovery requested
-		}
-		// Derivation needs a chain and device access, skip if either unavailable
-		w.stateLock.RLock()
-		if w.device == nil || w.deriveChain == nil || w.offline() {
-			w.stateLock.RUnlock()
-			reqc <- struct{}{}
-			continue
-		}
-		select {
-		case <-w.commsLock:
-		default:
-			w.stateLock.RUnlock()
-			reqc <- struct{}{}
-			continue
-		}
-		// Device lock obtained, derive the next batch of accounts
-		var (
-			accs  []accounts.Account
-			paths []accounts.DerivationPath
-
-			nextAddr = w.deriveNextAddr
-			nextPath = w.deriveNextPath
-
-			context = context.Background()
-		)
-		for empty := false; !empty; {
-			// Retrieve the next derived Ethereum account
-			if nextAddr == (common.Address{}) {
-				if nextAddr, err = w.ledgerDerive(nextPath); err != nil {
-					w.log.Warn("Ledger account derivation failed", "err", err)
-					break
-				}
-			}
-			// Check the account's status against the current chain state
-			var (
-				balance *big.Int
-				nonce   uint64
-			)
-			balance, err = w.deriveChain.BalanceAt(context, nextAddr, nil)
-			if err != nil {
-				w.log.Warn("Ledger balance retrieval failed", "err", err)
-				break
-			}
-			nonce, err = w.deriveChain.NonceAt(context, nextAddr, nil)
-			if err != nil {
-				w.log.Warn("Ledger nonce retrieval failed", "err", err)
-				break
-			}
-			// If the next account is empty, stop self-derivation, but add it nonetheless
-			if balance.Sign() == 0 && nonce == 0 {
-				empty = true
-			}
-			// We've just self-derived a new account, start tracking it locally
-			path := make(accounts.DerivationPath, len(nextPath))
-			copy(path[:], nextPath[:])
-			paths = append(paths, path)
-
-			account := accounts.Account{
-				Address: nextAddr,
-				URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
-			}
-			accs = append(accs, account)
-
-			// Display a log message to the user for new (or previously empty accounts)
-			if _, known := w.paths[nextAddr]; !known || (!empty && nextAddr == w.deriveNextAddr) {
-				w.log.Info("Ledger discovered new account", "address", nextAddr, "path", path, "balance", balance, "nonce", nonce)
-			}
-			// Fetch the next potential account
-			if !empty {
-				nextAddr = common.Address{}
-				nextPath[len(nextPath)-1]++
-			}
-		}
-		// Self derivation complete, release device lock
-		w.commsLock <- struct{}{}
-		w.stateLock.RUnlock()
-
-		// Insert any accounts successfully derived
-		w.stateLock.Lock()
-		for i := 0; i < len(accs); i++ {
-			if _, ok := w.paths[accs[i].Address]; !ok {
-				w.accounts = append(w.accounts, accs[i])
-				w.paths[accs[i].Address] = paths[i]
-			}
-		}
-		// Shift the self-derivation forward
-		// TODO(karalabe): don't overwrite changes from wallet.SelfDerive
-		w.deriveNextAddr = nextAddr
-		w.deriveNextPath = nextPath
-		w.stateLock.Unlock()
-
-		// Notify the user of termination and loop after a bit of time (to avoid trashing)
-		reqc <- struct{}{}
-		if err == nil {
-			select {
-			case errc = <-w.deriveQuit:
-				// Termination requested, abort
-			case <-time.After(selfDeriveThrottling):
-				// Waited enough, willing to self-derive again
-			}
-		}
-	}
-	// In case of error, wait for termination
-	if err != nil {
-		w.log.Debug("Ledger self-derivation failed", "err", err)
-		errc = <-w.deriveQuit
-	}
-	errc <- err
-}
-
-// Contains implements accounts.Wallet, returning whether a particular account is
-// or is not pinned into this Ledger instance. Although we could attempt to resolve
-// unpinned accounts, that would be an non-negligible hardware operation.
-func (w *ledgerWallet) Contains(account accounts.Account) bool {
-	w.stateLock.RLock()
-	defer w.stateLock.RUnlock()
-
-	_, exists := w.paths[account.Address]
-	return exists
-}
-
-// Derive implements accounts.Wallet, deriving a new account at the specific
-// derivation path. If pin is set to true, the account will be added to the list
-// of tracked accounts.
-func (w *ledgerWallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
-	// Try to derive the actual account and update its URL if successful
-	w.stateLock.RLock() // Avoid device disappearing during derivation
-
-	if w.device == nil || w.offline() {
-		w.stateLock.RUnlock()
-		return accounts.Account{}, accounts.ErrWalletClosed
-	}
-	<-w.commsLock // Avoid concurrent hardware access
-	address, err := w.ledgerDerive(path)
-	w.commsLock <- struct{}{}
-
-	w.stateLock.RUnlock()
-
-	// If an error occurred or no pinning was requested, return
-	if err != nil {
-		return accounts.Account{}, err
-	}
-	account := accounts.Account{
-		Address: address,
-		URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
-	}
-	if !pin {
-		return account, nil
-	}
-	// Pinning needs to modify the state
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	if _, ok := w.paths[address]; !ok {
-		w.accounts = append(w.accounts, account)
-		w.paths[address] = path
-	}
-	return account, nil
-}
-
-// SelfDerive implements accounts.Wallet, trying to discover accounts that the
-// user used previously (based on the chain state), but ones that he/she did not
-// explicitly pin to the wallet manually. To avoid chain head monitoring, self
-// derivation only runs during account listing (and even then throttled).
-func (w *ledgerWallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	w.deriveNextPath = make(accounts.DerivationPath, len(base))
-	copy(w.deriveNextPath[:], base[:])
-
-	w.deriveNextAddr = common.Address{}
-	w.deriveChain = chain
-}
-
-// SignHash implements accounts.Wallet, however signing arbitrary data is not
-// supported for Ledger wallets, so this method will always return an error.
-func (w *ledgerWallet) SignHash(acc accounts.Account, hash []byte) ([]byte, error) {
-	return nil, accounts.ErrNotSupported
-}
-
-// SignTx implements accounts.Wallet. It sends the transaction over to the Ledger
-// wallet to request a confirmation from the user. It returns either the signed
-// transaction or a failure if the user denied the transaction.
-//
-// Note, if the version of the Ethereum application running on the Ledger wallet is
-// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
-// will be returned opposed to silently signing in Homestead mode.
-func (w *ledgerWallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	w.stateLock.RLock() // Comms have own mutex, this is for the state fields
-	defer w.stateLock.RUnlock()
-
-	// If the wallet is closed, or the Ethereum app doesn't run, abort
-	if w.device == nil || w.offline() {
-		return nil, accounts.ErrWalletClosed
-	}
-	// Make sure the requested account is contained within
-	path, ok := w.paths[account.Address]
-	if !ok {
-		return nil, accounts.ErrUnknownAccount
-	}
-	// Ensure the wallet is capable of signing the given transaction
-	if chainID != nil && w.version[0] <= 1 && w.version[1] <= 0 && w.version[2] <= 2 {
-		return nil, fmt.Errorf("Ledger v%d.%d.%d doesn't support signing this transaction, please update to v1.0.3 at least", w.version[0], w.version[1], w.version[2])
-	}
-	// All infos gathered and metadata checks out, request signing
-	<-w.commsLock
-	defer func() { w.commsLock <- struct{}{} }()
-
-	// Ensure the device isn't screwed with while user confirmation is pending
-	// TODO(karalabe): remove if hotplug lands on Windows
-	w.hub.commsLock.Lock()
-	w.hub.commsPend++
-	w.hub.commsLock.Unlock()
-
-	defer func() {
-		w.hub.commsLock.Lock()
-		w.hub.commsPend--
-		w.hub.commsLock.Unlock()
-	}()
-	return w.ledgerSign(path, account.Address, tx, chainID)
-}
-
-// SignHashWithPassphrase implements accounts.Wallet, however signing arbitrary
-// data is not supported for Ledger wallets, so this method will always return
-// an error.
-func (w *ledgerWallet) SignHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
-	return nil, accounts.ErrNotSupported
-}
-
-// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
-// transaction with the given account using passphrase as extra authentication.
-// Since the Ledger does not support extra passphrases, it is silently ignored.
-func (w *ledgerWallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	return w.SignTx(account, tx, chainID)
-}
-
-// ledgerVersion retrieves the current version of the Ethereum wallet app running
-// on the Ledger wallet.
-//
-// The version retrieval protocol is defined as follows:
-//
-//   CLA | INS | P1 | P2 | Lc | Le
-//   ----+-----+----+----+----+---
-//    E0 | 06  | 00 | 00 | 00 | 04
-//
-// With no input data, and the output data being:
-//
-//   Description                                        | Length
-//   ---------------------------------------------------+--------
-//   Flags 01: arbitrary data signature enabled by user | 1 byte
-//   Application major version                          | 1 byte
-//   Application minor version                          | 1 byte
-//   Application patch version                          | 1 byte
-func (w *ledgerWallet) ledgerVersion() ([3]byte, error) {
-	// Send the request and wait for the response
-	reply, err := w.ledgerExchange(ledgerOpGetConfiguration, 0, 0, nil)
-	if err != nil {
-		return [3]byte{}, err
-	}
-	if len(reply) != 4 {
-		return [3]byte{}, errInvalidVersionReply
-	}
-	// Cache the version for future reference
-	var version [3]byte
-	copy(version[:], reply[1:])
-	return version, nil
-}
-
-// ledgerDerive retrieves the currently active Ethereum address from a Ledger
-// wallet at the specified derivation path.
-//
-// The address derivation protocol is defined as follows:
-//
-//   CLA | INS | P1 | P2 | Lc  | Le
-//   ----+-----+----+----+-----+---
-//    E0 | 02  | 00 return address
-//               01 display address and confirm before returning
-//                  | 00: do not return the chain code
-//                  | 01: return the chain code
-//                       | var | 00
-//
-// Where the input data is:
-//
-//   Description                                      | Length
-//   -------------------------------------------------+--------
-//   Number of BIP 32 derivations to perform (max 10) | 1 byte
-//   First derivation index (big endian)              | 4 bytes
-//   ...                                              | 4 bytes
-//   Last derivation index (big endian)               | 4 bytes
-//
-// And the output data is:
-//
-//   Description             | Length
-//   ------------------------+-------------------
-//   Public Key length       | 1 byte
-//   Uncompressed Public Key | arbitrary
-//   Ethereum address length | 1 byte
-//   Ethereum address        | 40 bytes hex ascii
-//   Chain code if requested | 32 bytes
-func (w *ledgerWallet) ledgerDerive(derivationPath []uint32) (common.Address, error) {
-	// Flatten the derivation path into the Ledger request
-	path := make([]byte, 1+4*len(derivationPath))
-	path[0] = byte(len(derivationPath))
-	for i, component := range derivationPath {
-		binary.BigEndian.PutUint32(path[1+4*i:], component)
-	}
-	// Send the request and wait for the response
-	reply, err := w.ledgerExchange(ledgerOpRetrieveAddress, ledgerP1DirectlyFetchAddress, ledgerP2DiscardAddressChainCode, path)
-	if err != nil {
-		return common.Address{}, err
-	}
-	// Discard the public key, we don't need that for now
-	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
-		return common.Address{}, errors.New("reply lacks public key entry")
-	}
-	reply = reply[1+int(reply[0]):]
-
-	// Extract the Ethereum hex address string
-	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
-		return common.Address{}, errors.New("reply lacks address entry")
-	}
-	hexstr := reply[1 : 1+int(reply[0])]
-
-	// Decode the hex sting into an Ethereum address and return
-	var address common.Address
-	hex.Decode(address[:], hexstr)
-	return address, nil
-}
-
-// ledgerSign sends the transaction to the Ledger wallet, and waits for the user
-// to confirm or deny the transaction.
-//
-// The transaction signing protocol is defined as follows:
-//
-//   CLA | INS | P1 | P2 | Lc  | Le
-//   ----+-----+----+----+-----+---
-//    E0 | 04  | 00: first transaction data block
-//               80: subsequent transaction data block
-//                  | 00 | variable | variable
-//
-// Where the input for the first transaction block (first 255 bytes) is:
-//
-//   Description                                      | Length
-//   -------------------------------------------------+----------
-//   Number of BIP 32 derivations to perform (max 10) | 1 byte
-//   First derivation index (big endian)              | 4 bytes
-//   ...                                              | 4 bytes
-//   Last derivation index (big endian)               | 4 bytes
-//   RLP transaction chunk                            | arbitrary
-//
-// And the input for subsequent transaction blocks (first 255 bytes) are:
-//
-//   Description           | Length
-//   ----------------------+----------
-//   RLP transaction chunk | arbitrary
-//
-// And the output data is:
-//
-//   Description | Length
-//   ------------+---------
-//   signature V | 1 byte
-//   signature R | 32 bytes
-//   signature S | 32 bytes
-func (w *ledgerWallet) ledgerSign(derivationPath []uint32, address common.Address, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	// Flatten the derivation path into the Ledger request
-	path := make([]byte, 1+4*len(derivationPath))
-	path[0] = byte(len(derivationPath))
-	for i, component := range derivationPath {
-		binary.BigEndian.PutUint32(path[1+4*i:], component)
-	}
-	// Create the transaction RLP based on whether legacy or EIP155 signing was requeste
-	var (
-		txrlp []byte
-		err   error
-	)
-	if chainID == nil {
-		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data()}); err != nil {
-			return nil, err
-		}
-	} else {
-		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data(), chainID, big.NewInt(0), big.NewInt(0)}); err != nil {
-			return nil, err
-		}
-	}
-	payload := append(path, txrlp...)
-
-	// Send the request and wait for the response
-	var (
-		op    = ledgerP1InitTransactionData
-		reply []byte
-	)
-	for len(payload) > 0 {
-		// Calculate the size of the next data chunk
-		chunk := 255
-		if chunk > len(payload) {
-			chunk = len(payload)
-		}
-		// Send the chunk over, ensuring it's processed correctly
-		reply, err = w.ledgerExchange(ledgerOpSignTransaction, op, 0, payload[:chunk])
-		if err != nil {
-			return nil, err
-		}
-		// Shift the payload and ensure subsequent chunks are marked as such
-		payload = payload[chunk:]
-		op = ledgerP1ContTransactionData
-	}
-	// Extract the Ethereum signature and do a sanity validation
-	if len(reply) != 65 {
-		return nil, errors.New("reply lacks signature")
-	}
-	signature := append(reply[1:], reply[0])
-
-	// Create the correct signer and signature transform based on the chain ID
-	var signer types.Signer
-	if chainID == nil {
-		signer = new(types.HomesteadSigner)
-	} else {
-		signer = types.NewEIP155Signer(chainID)
-		signature[64] = signature[64] - byte(chainID.Uint64()*2+35)
-	}
-	// Inject the final signature into the transaction and sanity check the sender
-	signed, err := tx.WithSignature(signer, signature)
-	if err != nil {
-		return nil, err
-	}
-	sender, err := types.Sender(signer, signed)
-	if err != nil {
-		return nil, err
-	}
-	if sender != address {
-		return nil, fmt.Errorf("signer mismatch: expected %s, got %s", address.Hex(), sender.Hex())
-	}
-	return signed, nil
-}
-
-// ledgerExchange performs a data exchange with the Ledger wallet, sending it a
-// message and retrieving the response.
-//
-// The common transport header is defined as follows:
-//
-//  Description                           | Length
-//  --------------------------------------+----------
-//  Communication channel ID (big endian) | 2 bytes
-//  Command tag                           | 1 byte
-//  Packet sequence index (big endian)    | 2 bytes
-//  Payload                               | arbitrary
-//
-// The Communication channel ID allows commands multiplexing over the same
-// physical link. It is not used for the time being, and should be set to 0101
-// to avoid compatibility issues with implementations ignoring a leading 00 byte.
-//
-// The Command tag describes the message content. Use TAG_APDU (0x05) for standard
-// APDU payloads, or TAG_PING (0x02) for a simple link test.
-//
-// The Packet sequence index describes the current sequence for fragmented payloads.
-// The first fragment index is 0x00.
-//
-// APDU Command payloads are encoded as follows:
-//
-//  Description              | Length
-//  -----------------------------------
-//  APDU length (big endian) | 2 bytes
-//  APDU CLA                 | 1 byte
-//  APDU INS                 | 1 byte
-//  APDU P1                  | 1 byte
-//  APDU P2                  | 1 byte
-//  APDU length              | 1 byte
-//  Optional APDU data       | arbitrary
-func (w *ledgerWallet) ledgerExchange(opcode ledgerOpcode, p1 ledgerParam1, p2 ledgerParam2, data []byte) ([]byte, error) {
-	// Construct the message payload, possibly split into multiple chunks
-	apdu := make([]byte, 2, 7+len(data))
-
-	binary.BigEndian.PutUint16(apdu, uint16(5+len(data)))
-	apdu = append(apdu, []byte{0xe0, byte(opcode), byte(p1), byte(p2), byte(len(data))}...)
-	apdu = append(apdu, data...)
-
-	// Stream all the chunks to the device
-	header := []byte{0x01, 0x01, 0x05, 0x00, 0x00} // Channel ID and command tag appended
-	chunk := make([]byte, 64)
-	space := len(chunk) - len(header)
-
-	for i := 0; len(apdu) > 0; i++ {
-		// Construct the new message to stream
-		chunk = append(chunk[:0], header...)
-		binary.BigEndian.PutUint16(chunk[3:], uint16(i))
-
-		if len(apdu) > space {
-			chunk = append(chunk, apdu[:space]...)
-			apdu = apdu[space:]
-		} else {
-			chunk = append(chunk, apdu...)
-			apdu = nil
-		}
-		// Send over to the device
-		w.log.Trace("Data chunk sent to the Ledger", "chunk", hexutil.Bytes(chunk))
-		if _, err := w.device.Write(chunk); err != nil {
-			return nil, err
-		}
-	}
-	// Stream the reply back from the wallet in 64 byte chunks
-	var reply []byte
-	chunk = chunk[:64] // Yeah, we surely have enough space
-	for {
-		// Read the next chunk from the Ledger wallet
-		if _, err := io.ReadFull(w.device, chunk); err != nil {
-			return nil, err
-		}
-		w.log.Trace("Data chunk received from the Ledger", "chunk", hexutil.Bytes(chunk))
-
-		// Make sure the transport header matches
-		if chunk[0] != 0x01 || chunk[1] != 0x01 || chunk[2] != 0x05 {
-			return nil, errReplyInvalidHeader
-		}
-		// If it's the first chunk, retrieve the total message length
-		var payload []byte
-
-		if chunk[3] == 0x00 && chunk[4] == 0x00 {
-			reply = make([]byte, 0, int(binary.BigEndian.Uint16(chunk[5:7])))
-			payload = chunk[7:]
-		} else {
-			payload = chunk[5:]
-		}
-		// Append to the reply and stop when filled up
-		if left := cap(reply) - len(reply); left > len(payload) {
-			reply = append(reply, payload...)
-		} else {
-			reply = append(reply, payload[:left]...)
-			break
-		}
-	}
-	return reply[:len(reply)-2], nil
-}
diff --git a/accounts/usbwallet/trezor.go b/accounts/usbwallet/trezor.go
new file mode 100644
index 000000000..159cb2ea9
--- /dev/null
+++ b/accounts/usbwallet/trezor.go
@@ -0,0 +1,330 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// This file contains the implementation for interacting with the Trezor hardware
+// wallets. The wire protocol spec can be found on the SatoshiLabs website:
+// https://doc.satoshilabs.com/trezor-tech/api-protobuf.html
+
+package usbwallet
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/usbwallet/internal/trezor"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/golang/protobuf/proto"
+)
+
+// ErrTrezorPINNeeded is returned if opening the trezor requires a PIN code. In
+// this case, the calling application should display a pinpad and send back the
+// encoded passphrase.
+var ErrTrezorPINNeeded = errors.New("trezor: pin needed")
+
+// errTrezorReplyInvalidHeader is the error message returned by a Trezor data exchange
+// if the device replies with a mismatching header. This usually means the device
+// is in browser mode.
+var errTrezorReplyInvalidHeader = errors.New("trezor: invalid reply header")
+
+// trezorDriver implements the communication with a Trezor hardware wallet.
+type trezorDriver struct {
+	device  io.ReadWriter // USB device connection to communicate through
+	version [3]uint32     // Current version of the Trezor firmware
+	label   string        // Current textual label of the Trezor device
+	pinwait bool          // Flags whether the device is waiting for PIN entry
+	failure error         // Any failure that would make the device unusable
+	log     log.Logger    // Contextual logger to tag the trezor with its id
+}
+
+// newTrezorDriver creates a new instance of a Trezor USB protocol driver.
+func newTrezorDriver(logger log.Logger) driver {
+	return &trezorDriver{
+		log: logger,
+	}
+}
+
+// Status implements accounts.Wallet, always whether the Trezor is opened, closed
+// or whether the Ethereum app was not started on it.
+func (w *trezorDriver) Status() (string, error) {
+	if w.failure != nil {
+		return fmt.Sprintf("Failed: %v", w.failure), w.failure
+	}
+	if w.device == nil {
+		return "Closed", w.failure
+	}
+	if w.pinwait {
+		return fmt.Sprintf("Trezor v%d.%d.%d '%s' waiting for PIN", w.version[0], w.version[1], w.version[2], w.label), w.failure
+	}
+	return fmt.Sprintf("Trezor v%d.%d.%d '%s' online", w.version[0], w.version[1], w.version[2], w.label), w.failure
+}
+
+// Open implements usbwallet.driver, attempting to initialize the connection to
+// the Trezor hardware wallet. Initializing the Trezor is a two phase operation:
+//  * The first phase is to initialize the connection and read the wallet's
+//    features. This phase is invoked is the provided passphrase is empty. The
+//    device will display the pinpad as a result and will return an appropriate
+//    error to notify the user that a second open phase is needed.
+//  * The second phase is to unlock access to the Trezor, which is done by the
+//    user actually providing a passphrase mapping a keyboard keypad to the pin
+//    number of the user (shuffled according to the pinpad displayed).
+func (w *trezorDriver) Open(device io.ReadWriter, passphrase string) error {
+	w.device, w.failure = device, nil
+
+	// If phase 1 is requested, init the connection and wait for user callback
+	if passphrase == "" {
+		// If we're already waiting for a PIN entry, insta-return
+		if w.pinwait {
+			return ErrTrezorPINNeeded
+		}
+		// Initialize a connection to the device
+		features := new(trezor.Features)
+		if _, err := w.trezorExchange(&trezor.Initialize{}, features); err != nil {
+			return err
+		}
+		w.version = [3]uint32{features.GetMajorVersion(), features.GetMinorVersion(), features.GetPatchVersion()}
+		w.label = features.GetLabel()
+
+		// Do a manual ping, forcing the device to ask for its PIN
+		askPin := true
+		res, err := w.trezorExchange(&trezor.Ping{PinProtection: &askPin}, new(trezor.PinMatrixRequest), new(trezor.Success))
+		if err != nil {
+			return err
+		}
+		// Only return the PIN request if the device wasn't unlocked until now
+		if res == 1 {
+			return nil // Device responded with trezor.Success
+		}
+		w.pinwait = true
+		return ErrTrezorPINNeeded
+	}
+	// Phase 2 requested with actual PIN entry
+	w.pinwait = false
+
+	if _, err := w.trezorExchange(&trezor.PinMatrixAck{Pin: &passphrase}, new(trezor.Success)); err != nil {
+		w.failure = err
+		return err
+	}
+	return nil
+}
+
+// Close implements usbwallet.driver, cleaning up and metadata maintained within
+// the Trezor driver.
+func (w *trezorDriver) Close() error {
+	w.version, w.label, w.pinwait = [3]uint32{}, "", false
+	return nil
+}
+
+// Heartbeat implements usbwallet.driver, performing a sanity check against the
+// Trezor to see if it's still online.
+func (w *trezorDriver) Heartbeat() error {
+	if _, err := w.trezorExchange(&trezor.Ping{}, new(trezor.Success)); err != nil {
+		w.failure = err
+		return err
+	}
+	return nil
+}
+
+// Derive implements usbwallet.driver, sending a derivation request to the Trezor
+// and returning the Ethereum address located on that derivation path.
+func (w *trezorDriver) Derive(path accounts.DerivationPath) (common.Address, error) {
+	return w.trezorDerive(path)
+}
+
+// SignTx implements usbwallet.driver, sending the transaction to the Trezor and
+// waiting for the user to confirm or deny the transaction.
+func (w *trezorDriver) SignTx(path accounts.DerivationPath, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
+	if w.device == nil {
+		return common.Address{}, nil, accounts.ErrWalletClosed
+	}
+	return w.trezorSign(path, tx, chainID)
+}
+
+// trezorDerive sends a derivation request to the Trezor device and returns the
+// Ethereum address located on that path.
+func (w *trezorDriver) trezorDerive(derivationPath []uint32) (common.Address, error) {
+	address := new(trezor.EthereumAddress)
+	if _, err := w.trezorExchange(&trezor.EthereumGetAddress{AddressN: derivationPath}, address); err != nil {
+		return common.Address{}, err
+	}
+	return common.BytesToAddress(address.GetAddress()), nil
+}
+
+// trezorSign sends the transaction to the Trezor wallet, and waits for the user
+// to confirm or deny the transaction.
+func (w *trezorDriver) trezorSign(derivationPath []uint32, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
+	// Create the transaction initiation message
+	data := tx.Data()
+	length := uint32(len(data))
+
+	request := &trezor.EthereumSignTx{
+		AddressN:   derivationPath,
+		Nonce:      new(big.Int).SetUint64(tx.Nonce()).Bytes(),
+		GasPrice:   tx.GasPrice().Bytes(),
+		GasLimit:   tx.Gas().Bytes(),
+		Value:      tx.Value().Bytes(),
+		DataLength: &length,
+	}
+	if to := tx.To(); to != nil {
+		request.To = (*to)[:] // Non contract deploy, set recipient explicitly
+	}
+	if length > 1024 { // Send the data chunked if that was requested
+		request.DataInitialChunk, data = data[:1024], data[1024:]
+	} else {
+		request.DataInitialChunk, data = data, nil
+	}
+	if chainID != nil { // EIP-155 transaction, set chain ID explicitly (only 32 bit is supported!?)
+		id := uint32(chainID.Int64())
+		request.ChainId = &id
+	}
+	// Send the initiation message and stream content until a signature is returned
+	response := new(trezor.EthereumTxRequest)
+	if _, err := w.trezorExchange(request, response); err != nil {
+		return common.Address{}, nil, err
+	}
+	for response.DataLength != nil && int(*response.DataLength) <= len(data) {
+		chunk := data[:*response.DataLength]
+		data = data[*response.DataLength:]
+
+		if _, err := w.trezorExchange(&trezor.EthereumTxAck{DataChunk: chunk}, response); err != nil {
+			return common.Address{}, nil, err
+		}
+	}
+	// Extract the Ethereum signature and do a sanity validation
+	if len(response.GetSignatureR()) == 0 || len(response.GetSignatureS()) == 0 || response.GetSignatureV() == 0 {
+		return common.Address{}, nil, errors.New("reply lacks signature")
+	}
+	signature := append(append(response.GetSignatureR(), response.GetSignatureS()...), byte(response.GetSignatureV()))
+
+	// Create the correct signer and signature transform based on the chain ID
+	var signer types.Signer
+	if chainID == nil {
+		signer = new(types.HomesteadSigner)
+	} else {
+		signer = types.NewEIP155Signer(chainID)
+		signature[64] = signature[64] - byte(chainID.Uint64()*2+35)
+	}
+	// Inject the final signature into the transaction and sanity check the sender
+	signed, err := tx.WithSignature(signer, signature)
+	if err != nil {
+		return common.Address{}, nil, err
+	}
+	sender, err := types.Sender(signer, signed)
+	if err != nil {
+		return common.Address{}, nil, err
+	}
+	return sender, signed, nil
+}
+
+// trezorExchange performs a data exchange with the Trezor wallet, sending it a
+// message and retrieving the response. If multiple responses are possible, the
+// method will also return the index of the destination object used.
+func (w *trezorDriver) trezorExchange(req proto.Message, results ...proto.Message) (int, error) {
+	// Construct the original message payload to chunk up
+	data, err := proto.Marshal(req)
+	if err != nil {
+		return 0, err
+	}
+	payload := make([]byte, 8+len(data))
+	copy(payload, []byte{0x23, 0x23})
+	binary.BigEndian.PutUint16(payload[2:], trezor.Type(req))
+	binary.BigEndian.PutUint32(payload[4:], uint32(len(data)))
+	copy(payload[8:], data)
+
+	// Stream all the chunks to the device
+	chunk := make([]byte, 64)
+	chunk[0] = 0x3f // Report ID magic number
+
+	for len(payload) > 0 {
+		// Construct the new message to stream, padding with zeroes if needed
+		if len(payload) > 63 {
+			copy(chunk[1:], payload[:63])
+			payload = payload[63:]
+		} else {
+			copy(chunk[1:], payload)
+			copy(chunk[1+len(payload):], make([]byte, 63-len(payload)))
+			payload = nil
+		}
+		// Send over to the device
+		w.log.Trace("Data chunk sent to the Trezor", "chunk", hexutil.Bytes(chunk))
+		if _, err := w.device.Write(chunk); err != nil {
+			return 0, err
+		}
+	}
+	// Stream the reply back from the wallet in 64 byte chunks
+	var (
+		kind  uint16
+		reply []byte
+	)
+	for {
+		// Read the next chunk from the Trezor wallet
+		if _, err := io.ReadFull(w.device, chunk); err != nil {
+			return 0, err
+		}
+		w.log.Trace("Data chunk received from the Trezor", "chunk", hexutil.Bytes(chunk))
+
+		// Make sure the transport header matches
+		if chunk[0] != 0x3f || (len(reply) == 0 && (chunk[1] != 0x23 || chunk[2] != 0x23)) {
+			return 0, errTrezorReplyInvalidHeader
+		}
+		// If it's the first chunk, retrieve the reply message type and total message length
+		var payload []byte
+
+		if len(reply) == 0 {
+			kind = binary.BigEndian.Uint16(chunk[3:5])
+			reply = make([]byte, 0, int(binary.BigEndian.Uint32(chunk[5:9])))
+			payload = chunk[9:]
+		} else {
+			payload = chunk[1:]
+		}
+		// Append to the reply and stop when filled up
+		if left := cap(reply) - len(reply); left > len(payload) {
+			reply = append(reply, payload...)
+		} else {
+			reply = append(reply, payload[:left]...)
+			break
+		}
+	}
+	// Try to parse the reply into the requested reply message
+	if kind == uint16(trezor.MessageType_MessageType_Failure) {
+		// Trezor returned a failure, extract and return the message
+		failure := new(trezor.Failure)
+		if err := proto.Unmarshal(reply, failure); err != nil {
+			return 0, err
+		}
+		return 0, errors.New("trezor: " + failure.GetMessage())
+	}
+	if kind == uint16(trezor.MessageType_MessageType_ButtonRequest) {
+		// Trezor is waiting for user confirmation, ack and wait for the next message
+		return w.trezorExchange(&trezor.ButtonAck{}, results...)
+	}
+	for i, res := range results {
+		if trezor.Type(res) == kind {
+			return i, proto.Unmarshal(reply, res)
+		}
+	}
+	expected := make([]string, len(results))
+	for i, res := range results {
+		expected[i] = trezor.Name(trezor.Type(res))
+	}
+	return 0, fmt.Errorf("trezor: expected reply types %s, got %s", expected, trezor.Name(kind))
+}
diff --git a/accounts/usbwallet/trezor_hub.go b/accounts/usbwallet/trezor_hub.go
deleted file mode 100644
index 5681a55c7..000000000
--- a/accounts/usbwallet/trezor_hub.go
+++ /dev/null
@@ -1,210 +0,0 @@
-// Copyright 2017 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package usbwallet
-
-import (
-	"errors"
-	"runtime"
-	"sync"
-	"time"
-
-	"github.com/ethereum/go-ethereum/accounts"
-	"github.com/ethereum/go-ethereum/event"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/karalabe/hid"
-)
-
-// TrezorScheme is the protocol scheme prefixing account and wallet URLs.
-var TrezorScheme = "trezor"
-
-// trezorVendorID is the USB vendor ID for SatoshiLabs.
-var trezorVendorID = uint16(0x534c)
-
-// trezorDeviceID is the USB device ID for the Trezor 1.
-var trezorDeviceID = uint16(0x0001)
-
-// Maximum time between wallet refreshes (if USB hotplug notifications don't work).
-const trezorRefreshCycle = time.Second
-
-// Minimum time between wallet refreshes to avoid USB trashing.
-const trezorRefreshThrottling = 500 * time.Millisecond
-
-// TrezorHub is a accounts.Backend that can find and handle Trezor hardware wallets.
-type TrezorHub struct {
-	refreshed   time.Time               // Time instance when the list of wallets was last refreshed
-	wallets     []accounts.Wallet       // List of Trezor devices currently tracking
-	updateFeed  event.Feed              // Event feed to notify wallet additions/removals
-	updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
-	updating    bool                    // Whether the event notification loop is running
-
-	quit chan chan error
-
-	stateLock sync.RWMutex // Protects the internals of the hub from racey access
-
-	// TODO(karalabe): remove if hotplug lands on Windows
-	commsPend int        // Number of operations blocking enumeration
-	commsLock sync.Mutex // Lock protecting the pending counter and enumeration
-}
-
-// NewTrezorHub creates a new hardware wallet manager for Trezor devices.
-func NewTrezorHub() (*TrezorHub, error) {
-	if !hid.Supported() {
-		return nil, errors.New("unsupported platform")
-	}
-	hub := &TrezorHub{
-		quit: make(chan chan error),
-	}
-	hub.refreshWallets()
-	return hub, nil
-}
-
-// Wallets implements accounts.Backend, returning all the currently tracked USB
-// devices that appear to be Trezor hardware wallets.
-func (hub *TrezorHub) Wallets() []accounts.Wallet {
-	// Make sure the list of wallets is up to date
-	hub.refreshWallets()
-
-	hub.stateLock.RLock()
-	defer hub.stateLock.RUnlock()
-
-	cpy := make([]accounts.Wallet, len(hub.wallets))
-	copy(cpy, hub.wallets)
-	return cpy
-}
-
-// refreshWallets scans the USB devices attached to the machine and updates the
-// list of wallets based on the found devices.
-func (hub *TrezorHub) refreshWallets() {
-	// Don't scan the USB like crazy it the user fetches wallets in a loop
-	hub.stateLock.RLock()
-	elapsed := time.Since(hub.refreshed)
-	hub.stateLock.RUnlock()
-
-	if elapsed < trezorRefreshThrottling {
-		return
-	}
-	// Retrieve the current list of Trezor devices
-	var trezors []hid.DeviceInfo
-
-	if runtime.GOOS == "linux" {
-		// hidapi on Linux opens the device during enumeration to retrieve some infos,
-		// breaking the Trezor protocol if that is waiting for user confirmation. This
-		// is a bug acknowledged at Trezor, but it won't be fixed on old devices so we
-		// need to prevent concurrent comms ourselves. The more elegant solution would
-		// be to ditch enumeration in favor of hutplug events, but that don't work yet
-		// on Windows so if we need to hack it anyway, this is more elegant for now.
-		hub.commsLock.Lock()
-		if hub.commsPend > 0 { // A confirmation is pending, don't refresh
-			hub.commsLock.Unlock()
-			return
-		}
-	}
-	for _, info := range hid.Enumerate(trezorVendorID, trezorDeviceID) {
-		if info.Interface == 0 { // interface #1 is the debug link, skip it
-			trezors = append(trezors, info)
-		}
-	}
-	if runtime.GOOS == "linux" {
-		// See rationale before the enumeration why this is needed and only on Linux.
-		hub.commsLock.Unlock()
-	}
-	// Transform the current list of wallets into the new one
-	hub.stateLock.Lock()
-
-	wallets := make([]accounts.Wallet, 0, len(trezors))
-	events := []accounts.WalletEvent{}
-
-	for _, trezor := range trezors {
-		url := accounts.URL{Scheme: TrezorScheme, Path: trezor.Path}
-
-		// Drop wallets in front of the next device or those that failed for some reason
-		for len(hub.wallets) > 0 && (hub.wallets[0].URL().Cmp(url) < 0 || hub.wallets[0].(*trezorWallet).failed()) {
-			events = append(events, accounts.WalletEvent{Wallet: hub.wallets[0], Kind: accounts.WalletDropped})
-			hub.wallets = hub.wallets[1:]
-		}
-		// If there are no more wallets or the device is before the next, wrap new wallet
-		if len(hub.wallets) == 0 || hub.wallets[0].URL().Cmp(url) > 0 {
-			wallet := &trezorWallet{hub: hub, url: &url, info: trezor, log: log.New("url", url)}
-
-			events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletArrived})
-			wallets = append(wallets, wallet)
-			continue
-		}
-		// If the device is the same as the first wallet, keep it
-		if hub.wallets[0].URL().Cmp(url) == 0 {
-			wallets = append(wallets, hub.wallets[0])
-			hub.wallets = hub.wallets[1:]
-			continue
-		}
-	}
-	// Drop any leftover wallets and set the new batch
-	for _, wallet := range hub.wallets {
-		events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
-	}
-	hub.refreshed = time.Now()
-	hub.wallets = wallets
-	hub.stateLock.Unlock()
-
-	// Fire all wallet events and return
-	for _, event := range events {
-		hub.updateFeed.Send(event)
-	}
-}
-
-// Subscribe implements accounts.Backend, creating an async subscription to
-// receive notifications on the addition or removal of Trezor wallets.
-func (hub *TrezorHub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
-	// We need the mutex to reliably start/stop the update loop
-	hub.stateLock.Lock()
-	defer hub.stateLock.Unlock()
-
-	// Subscribe the caller and track the subscriber count
-	sub := hub.updateScope.Track(hub.updateFeed.Subscribe(sink))
-
-	// Subscribers require an active notification loop, start it
-	if !hub.updating {
-		hub.updating = true
-		go hub.updater()
-	}
-	return sub
-}
-
-// updater is responsible for maintaining an up-to-date list of wallets stored in
-// the keystore, and for firing wallet addition/removal events. It listens for
-// account change events from the underlying account cache, and also periodically
-// forces a manual refresh (only triggers for systems where the filesystem notifier
-// is not running).
-func (hub *TrezorHub) updater() {
-	for {
-		// Wait for a USB hotplug event (not supported yet) or a refresh timeout
-		select {
-		//case <-hub.changes: // reenable on hutplug implementation
-		case <-time.After(trezorRefreshCycle):
-		}
-		// Run the wallet refresher
-		hub.refreshWallets()
-
-		// If all our subscribers left, stop the updater
-		hub.stateLock.Lock()
-		if hub.updateScope.Count() == 0 {
-			hub.updating = false
-			hub.stateLock.Unlock()
-			return
-		}
-		hub.stateLock.Unlock()
-	}
-}
diff --git a/accounts/usbwallet/trezor_wallet.go b/accounts/usbwallet/trezor_wallet.go
deleted file mode 100644
index 779119192..000000000
--- a/accounts/usbwallet/trezor_wallet.go
+++ /dev/null
@@ -1,761 +0,0 @@
-// Copyright 2017 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-// This file contains the implementation for interacting with the Trezor hardware
-// wallets. The wire protocol spec can be found on the SatoshiLabs website:
-// https://doc.satoshilabs.com/trezor-tech/api-protobuf.html
-
-package usbwallet
-
-import (
-	"context"
-	"encoding/binary"
-	"errors"
-	"fmt"
-	"io"
-	"math/big"
-	"sync"
-	"time"
-
-	ethereum "github.com/ethereum/go-ethereum"
-	"github.com/ethereum/go-ethereum/accounts"
-	"github.com/ethereum/go-ethereum/accounts/usbwallet/internal/trezor"
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/hexutil"
-	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/log"
-	"github.com/golang/protobuf/proto"
-	"github.com/karalabe/hid"
-)
-
-// ErrTrezorPINNeeded is returned if opening the trezor requires a PIN code. In
-// this case, the calling application should display a pinpad and send back the
-// encoded passphrase.
-var ErrTrezorPINNeeded = errors.New("trezor: pin needed")
-
-// trezorWallet represents a live USB Trezor hardware wallet.
-type trezorWallet struct {
-	hub *TrezorHub    // USB hub the device originates from (TODO(karalabe): remove if hotplug lands on Windows)
-	url *accounts.URL // Textual URL uniquely identifying this wallet
-
-	info    hid.DeviceInfo // Known USB device infos about the wallet
-	device  *hid.Device    // USB device advertising itself as a Trezor wallet
-	failure error          // Any failure that would make the device unusable
-
-	version  [3]uint32                                  // Current version of the Trezor formware (zero if app is offline)
-	label    string                                     // Current textual label of the Trezor device
-	pinwait  bool                                       // Flags whether the device is waiting for PIN entry
-	accounts []accounts.Account                         // List of derive accounts pinned on the Trezor
-	paths    map[common.Address]accounts.DerivationPath // Known derivation paths for signing operations
-
-	deriveNextPath accounts.DerivationPath   // Next derivation path for account auto-discovery
-	deriveNextAddr common.Address            // Next derived account address for auto-discovery
-	deriveChain    ethereum.ChainStateReader // Blockchain state reader to discover used account with
-	deriveReq      chan chan struct{}        // Channel to request a self-derivation on
-	deriveQuit     chan chan error           // Channel to terminate the self-deriver with
-
-	healthQuit chan chan error
-
-	// Locking a hardware wallet is a bit special. Since hardware devices are lower
-	// performing, any communication with them might take a non negligible amount of
-	// time. Worse still, waiting for user confirmation can take arbitrarily long,
-	// but exclusive communication must be upheld during. Locking the entire wallet
-	// in the mean time however would stall any parts of the system that don't want
-	// to communicate, just read some state (e.g. list the accounts).
-	//
-	// As such, a hardware wallet needs two locks to function correctly. A state
-	// lock can be used to protect the wallet's software-side internal state, which
-	// must not be held exlusively during hardware communication. A communication
-	// lock can be used to achieve exclusive access to the device itself, this one
-	// however should allow "skipping" waiting for operations that might want to
-	// use the device, but can live without too (e.g. account self-derivation).
-	//
-	// Since we have two locks, it's important to know how to properly use them:
-	//   - Communication requires the `device` to not change, so obtaining the
-	//     commsLock should be done after having a stateLock.
-	//   - Communication must not disable read access to the wallet state, so it
-	//     must only ever hold a *read* lock to stateLock.
-	commsLock chan struct{} // Mutex (buf=1) for the USB comms without keeping the state locked
-	stateLock sync.RWMutex  // Protects read and write access to the wallet struct fields
-
-	log log.Logger // Contextual logger to tag the trezor with its id
-}
-
-// URL implements accounts.Wallet, returning the URL of the Trezor device.
-func (w *trezorWallet) URL() accounts.URL {
-	return *w.url // Immutable, no need for a lock
-}
-
-// Status implements accounts.Wallet, always whether the Trezor is opened, closed
-// or whether the Ethereum app was not started on it.
-func (w *trezorWallet) Status() string {
-	w.stateLock.RLock() // No device communication, state lock is enough
-	defer w.stateLock.RUnlock()
-
-	if w.failure != nil {
-		return fmt.Sprintf("Failed: %v", w.failure)
-	}
-	if w.device == nil {
-		return "Closed"
-	}
-	if w.pinwait {
-		return fmt.Sprintf("Trezor v%d.%d.%d '%s' waiting for PIN", w.version[0], w.version[1], w.version[2], w.label)
-	}
-	return fmt.Sprintf("Trezor v%d.%d.%d '%s' online", w.version[0], w.version[1], w.version[2], w.label)
-}
-
-// failed returns if the USB device wrapped by the wallet failed for some reason.
-// This is used by the device scanner to report failed wallets as departed.
-//
-// The method assumes that the state lock is *not* held!
-func (w *trezorWallet) failed() bool {
-	w.stateLock.RLock() // No device communication, state lock is enough
-	defer w.stateLock.RUnlock()
-
-	return w.failure != nil
-}
-
-// Open implements accounts.Wallet, attempting to open a USB connection to the
-// Trezor hardware wallet. Connecting to the Trezor is a two phase operation:
-//  * The first phase is to establish the USB connection, initialize it and read
-//    the wallet's features. This phase is invoked is the provided passphrase is
-//    empty. The device will display the pinpad as a result and will return an
-//    appropriate error to notify the user that a second open phase is needed.
-//  * The second phase is to unlock access to the Trezor, which is done by the
-//    user actually providing a passphrase mapping a keyboard keypad to the pin
-//    number of the user (shuffled according to the pinpad displayed).
-func (w *trezorWallet) Open(passphrase string) error {
-	w.stateLock.Lock() // State lock is enough since there's no connection yet at this point
-	defer w.stateLock.Unlock()
-
-	// If phase 1 is requested, init the connection and wait for user callback
-	if passphrase == "" {
-		// If we're already waiting for a PIN entry, insta-return
-		if w.pinwait {
-			return ErrTrezorPINNeeded
-		}
-		// Initialize a connection to the device
-		if err := w.openInit(); err != nil {
-			return err
-		}
-		// Do a manual ping, forcing the device to ask for its PIN
-		askPin, pinRequest := true, new(trezor.PinMatrixRequest)
-		if err := w.trezorExchange(&trezor.Ping{PinProtection: &askPin}, pinRequest); err != nil {
-			return err
-		}
-		w.pinwait = true
-
-		return ErrTrezorPINNeeded
-	}
-	// Phase 2 requested with actual PIN entry
-	w.pinwait = false
-
-	success := new(trezor.Success)
-	if err := w.trezorExchange(&trezor.PinMatrixAck{Pin: &passphrase}, success); err != nil {
-		w.failure = err
-		return err
-	}
-	go w.hub.updateFeed.Send(accounts.WalletEvent{Wallet: w, Kind: accounts.WalletOpened})
-
-	// Trezor unlocked, start the heartbeat cycle and account derivation
-	w.paths = make(map[common.Address]accounts.DerivationPath)
-
-	w.deriveReq = make(chan chan struct{})
-	w.deriveQuit = make(chan chan error)
-	w.healthQuit = make(chan chan error)
-
-	defer func() {
-		go w.heartbeat()
-		go w.selfDerive()
-	}()
-	return nil
-}
-
-// openInit is the first phase of a Trezor opening mechanism which initializes
-//  device connection and requests the device to display the pinpad.
-func (w *trezorWallet) openInit() error {
-	// If the wallet was already opened, don't try to phase-1 open again
-	if w.device != nil {
-		return accounts.ErrWalletAlreadyOpen
-	}
-	// Otherwise iterate over all USB devices and find this again (no way to directly do this)
-	device, err := w.info.Open()
-	if err != nil {
-		return err
-	}
-	// Wallet successfully connected to, init the connection and start the heartbeat
-	w.device = device
-	w.commsLock = make(chan struct{}, 1)
-	w.commsLock <- struct{}{} // Enable lock
-
-	// Retrieve the Trezor's version number and user label
-	features := new(trezor.Features)
-	if err := w.trezorExchange(&trezor.Initialize{}, features); err != nil {
-		return err
-	}
-	w.version = [3]uint32{features.GetMajorVersion(), features.GetMinorVersion(), features.GetPatchVersion()}
-	w.label = features.GetLabel()
-
-	return nil
-}
-
-// heartbeat is a health check loop for the Trezor wallets to periodically verify
-// whether they are still present or if they malfunctioned. It is needed because:
-//  - libusb on Windows doesn't support hotplug, so we can't detect USB unplugs
-func (w *trezorWallet) heartbeat() {
-	w.log.Debug("Trezor health-check started")
-	defer w.log.Debug("Trezor health-check stopped")
-
-	// Execute heartbeat checks until termination or error
-	var (
-		errc chan error
-		err  error
-	)
-	for errc == nil && err == nil {
-		// Wait until termination is requested or the heartbeat cycle arrives
-		select {
-		case errc = <-w.healthQuit:
-			// Termination requested
-			continue
-		case <-time.After(heartbeatCycle):
-			// Heartbeat time
-		}
-		// Execute a tiny data exchange to see responsiveness
-		w.stateLock.RLock()
-		if w.device == nil {
-			// Terminated while waiting for the lock
-			w.stateLock.RUnlock()
-			continue
-		}
-		<-w.commsLock // Don't lock state while executing ping
-
-		success := new(trezor.Success)
-		err = w.trezorExchange(&trezor.Ping{}, success)
-
-		w.commsLock <- struct{}{}
-		w.stateLock.RUnlock()
-
-		if err != nil {
-			w.stateLock.Lock() // Lock state to tear the wallet down
-			w.failure = err
-			w.close()
-			w.stateLock.Unlock()
-		}
-		// Ignore non hardware related errors
-		err = nil
-	}
-	// In case of error, wait for termination
-	if err != nil {
-		w.log.Debug("Trezor health-check failed", "err", err)
-		errc = <-w.healthQuit
-	}
-	errc <- err
-}
-
-// Close implements accounts.Wallet, closing the USB connection to the Trezor.
-func (w *trezorWallet) Close() error {
-	// Ensure the wallet was opened
-	w.stateLock.RLock()
-	hQuit, dQuit := w.healthQuit, w.deriveQuit
-	w.stateLock.RUnlock()
-
-	// Terminate the health checks
-	var herr error
-	if hQuit != nil {
-		errc := make(chan error)
-		hQuit <- errc
-		herr = <-errc // Save for later, we *must* close the USB
-	}
-	// Terminate the self-derivations
-	var derr error
-	if dQuit != nil {
-		errc := make(chan error)
-		dQuit <- errc
-		derr = <-errc // Save for later, we *must* close the USB
-	}
-	// Terminate the device connection
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	w.healthQuit = nil
-	w.deriveQuit = nil
-	w.deriveReq = nil
-
-	if err := w.close(); err != nil {
-		return err
-	}
-	if herr != nil {
-		return herr
-	}
-	return derr
-}
-
-// close is the internal wallet closer that terminates the USB connection and
-// resets all the fields to their defaults.
-//
-// Note, close assumes the state lock is held!
-func (w *trezorWallet) close() error {
-	// Allow duplicate closes, especially for health-check failures
-	if w.device == nil {
-		return nil
-	}
-	// Close the device, clear everything, then return
-	w.device.Close()
-	w.device = nil
-
-	w.label, w.version = "", [3]uint32{}
-	w.accounts, w.paths = nil, nil
-
-	return nil
-}
-
-// Accounts implements accounts.Wallet, returning the list of accounts pinned to
-// the Trezor hardware wallet. If self-derivation was enabled, the account list
-// is periodically expanded based on current chain state.
-func (w *trezorWallet) Accounts() []accounts.Account {
-	// Attempt self-derivation if it's running
-	reqc := make(chan struct{}, 1)
-	select {
-	case w.deriveReq <- reqc:
-		// Self-derivation request accepted, wait for it
-		<-reqc
-	default:
-		// Self-derivation offline, throttled or busy, skip
-	}
-	// Return whatever account list we ended up with
-	w.stateLock.RLock()
-	defer w.stateLock.RUnlock()
-
-	cpy := make([]accounts.Account, len(w.accounts))
-	copy(cpy, w.accounts)
-	return cpy
-}
-
-// selfDerive is an account derivation loop that upon request attempts to find
-// new non-zero accounts.
-func (w *trezorWallet) selfDerive() {
-	w.log.Debug("Trezor self-derivation started")
-	defer w.log.Debug("Trezor self-derivation stopped")
-
-	// Execute self-derivations until termination or error
-	var (
-		reqc chan struct{}
-		errc chan error
-		err  error
-	)
-	for errc == nil && err == nil {
-		// Wait until either derivation or termination is requested
-		select {
-		case errc = <-w.deriveQuit:
-			// Termination requested
-			continue
-		case reqc = <-w.deriveReq:
-			// Account discovery requested
-		}
-		// Derivation needs a chain and device access, skip if either unavailable
-		w.stateLock.RLock()
-		if w.device == nil || w.deriveChain == nil {
-			w.stateLock.RUnlock()
-			reqc <- struct{}{}
-			continue
-		}
-		select {
-		case <-w.commsLock:
-		default:
-			w.stateLock.RUnlock()
-			reqc <- struct{}{}
-			continue
-		}
-		// Device lock obtained, derive the next batch of accounts
-		var (
-			accs  []accounts.Account
-			paths []accounts.DerivationPath
-
-			nextAddr = w.deriveNextAddr
-			nextPath = w.deriveNextPath
-
-			context = context.Background()
-		)
-		for empty := false; !empty; {
-			// Retrieve the next derived Ethereum account
-			if nextAddr == (common.Address{}) {
-				if nextAddr, err = w.trezorDerive(nextPath); err != nil {
-					w.log.Warn("Trezor account derivation failed", "err", err)
-					break
-				}
-			}
-			// Check the account's status against the current chain state
-			var (
-				balance *big.Int
-				nonce   uint64
-			)
-			balance, err = w.deriveChain.BalanceAt(context, nextAddr, nil)
-			if err != nil {
-				w.log.Warn("Trezor balance retrieval failed", "err", err)
-				break
-			}
-			nonce, err = w.deriveChain.NonceAt(context, nextAddr, nil)
-			if err != nil {
-				w.log.Warn("Trezor nonce retrieval failed", "err", err)
-				break
-			}
-			// If the next account is empty, stop self-derivation, but add it nonetheless
-			if balance.Sign() == 0 && nonce == 0 {
-				empty = true
-			}
-			// We've just self-derived a new account, start tracking it locally
-			path := make(accounts.DerivationPath, len(nextPath))
-			copy(path[:], nextPath[:])
-			paths = append(paths, path)
-
-			account := accounts.Account{
-				Address: nextAddr,
-				URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
-			}
-			accs = append(accs, account)
-
-			// Display a log message to the user for new (or previously empty accounts)
-			if _, known := w.paths[nextAddr]; !known || (!empty && nextAddr == w.deriveNextAddr) {
-				w.log.Info("Trezor discovered new account", "address", nextAddr, "path", path, "balance", balance, "nonce", nonce)
-			}
-			// Fetch the next potential account
-			if !empty {
-				nextAddr = common.Address{}
-				nextPath[len(nextPath)-1]++
-			}
-		}
-		// Self derivation complete, release device lock
-		w.commsLock <- struct{}{}
-		w.stateLock.RUnlock()
-
-		// Insert any accounts successfully derived
-		w.stateLock.Lock()
-		for i := 0; i < len(accs); i++ {
-			if _, ok := w.paths[accs[i].Address]; !ok {
-				w.accounts = append(w.accounts, accs[i])
-				w.paths[accs[i].Address] = paths[i]
-			}
-		}
-		// Shift the self-derivation forward
-		// TODO(karalabe): don't overwrite changes from wallet.SelfDerive
-		w.deriveNextAddr = nextAddr
-		w.deriveNextPath = nextPath
-		w.stateLock.Unlock()
-
-		// Notify the user of termination and loop after a bit of time (to avoid trashing)
-		reqc <- struct{}{}
-		if err == nil {
-			select {
-			case errc = <-w.deriveQuit:
-				// Termination requested, abort
-			case <-time.After(selfDeriveThrottling):
-				// Waited enough, willing to self-derive again
-			}
-		}
-	}
-	// In case of error, wait for termination
-	if err != nil {
-		w.log.Debug("Trezor self-derivation failed", "err", err)
-		errc = <-w.deriveQuit
-	}
-	errc <- err
-}
-
-// Contains implements accounts.Wallet, returning whether a particular account is
-// or is not pinned into this Trezor instance. Although we could attempt to resolve
-// unpinned accounts, that would be an non-negligible hardware operation.
-func (w *trezorWallet) Contains(account accounts.Account) bool {
-	w.stateLock.RLock()
-	defer w.stateLock.RUnlock()
-
-	_, exists := w.paths[account.Address]
-	return exists
-}
-
-// Derive implements accounts.Wallet, deriving a new account at the specific
-// derivation path. If pin is set to true, the account will be added to the list
-// of tracked accounts.
-func (w *trezorWallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
-	// Try to derive the actual account and update its URL if successful
-	w.stateLock.RLock() // Avoid device disappearing during derivation
-
-	if w.device == nil {
-		w.stateLock.RUnlock()
-		return accounts.Account{}, accounts.ErrWalletClosed
-	}
-	<-w.commsLock // Avoid concurrent hardware access
-	address, err := w.trezorDerive(path)
-	w.commsLock <- struct{}{}
-
-	w.stateLock.RUnlock()
-
-	// If an error occurred or no pinning was requested, return
-	if err != nil {
-		return accounts.Account{}, err
-	}
-	account := accounts.Account{
-		Address: address,
-		URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
-	}
-	if !pin {
-		return account, nil
-	}
-	// Pinning needs to modify the state
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	if _, ok := w.paths[address]; !ok {
-		w.accounts = append(w.accounts, account)
-		w.paths[address] = path
-	}
-	return account, nil
-}
-
-// SelfDerive implements accounts.Wallet, trying to discover accounts that the
-// user used previously (based on the chain state), but ones that he/she did not
-// explicitly pin to the wallet manually. To avoid chain head monitoring, self
-// derivation only runs during account listing (and even then throttled).
-func (w *trezorWallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {
-	w.stateLock.Lock()
-	defer w.stateLock.Unlock()
-
-	w.deriveNextPath = make(accounts.DerivationPath, len(base))
-	copy(w.deriveNextPath[:], base[:])
-
-	w.deriveNextAddr = common.Address{}
-	w.deriveChain = chain
-}
-
-// SignHash implements accounts.Wallet, however signing arbitrary data is not
-// supported for Trezor wallets, so this method will always return an error.
-func (w *trezorWallet) SignHash(acc accounts.Account, hash []byte) ([]byte, error) {
-	return nil, accounts.ErrNotSupported
-}
-
-// SignTx implements accounts.Wallet. It sends the transaction over to the Trezor
-// wallet to request a confirmation from the user. It returns either the signed
-// transaction or a failure if the user denied the transaction.
-func (w *trezorWallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	w.stateLock.RLock() // Comms have own mutex, this is for the state fields
-	defer w.stateLock.RUnlock()
-
-	// If the wallet is closed, abort
-	if w.device == nil {
-		return nil, accounts.ErrWalletClosed
-	}
-	// Make sure the requested account is contained within
-	path, ok := w.paths[account.Address]
-	if !ok {
-		return nil, accounts.ErrUnknownAccount
-	}
-	// All infos gathered and metadata checks out, request signing
-	<-w.commsLock
-	defer func() { w.commsLock <- struct{}{} }()
-
-	// Ensure the device isn't screwed with while user confirmation is pending
-	// TODO(karalabe): remove if hotplug lands on Windows
-	w.hub.commsLock.Lock()
-	w.hub.commsPend++
-	w.hub.commsLock.Unlock()
-
-	defer func() {
-		w.hub.commsLock.Lock()
-		w.hub.commsPend--
-		w.hub.commsLock.Unlock()
-	}()
-
-	return w.trezorSign(path, account.Address, tx, chainID)
-}
-
-// SignHashWithPassphrase implements accounts.Wallet, however signing arbitrary
-// data is not supported for Trezor wallets, so this method will always return
-// an error.
-func (w *trezorWallet) SignHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
-	return nil, accounts.ErrNotSupported
-}
-
-// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
-// transaction with the given account using passphrase as extra authentication.
-// Since the Trezor does not support extra passphrases, it is silently ignored.
-func (w *trezorWallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	return w.SignTx(account, tx, chainID)
-}
-
-// trezorDerive sends a derivation request to the Trezor device and returns the
-// Ethereum address located on that path.
-func (w *trezorWallet) trezorDerive(derivationPath []uint32) (common.Address, error) {
-	address := new(trezor.EthereumAddress)
-	if err := w.trezorExchange(&trezor.EthereumGetAddress{AddressN: derivationPath}, address); err != nil {
-		return common.Address{}, err
-	}
-	return common.BytesToAddress(address.GetAddress()), nil
-}
-
-// trezorSign sends the transaction to the Trezor wallet, and waits for the user
-// to confirm or deny the transaction.
-func (w *trezorWallet) trezorSign(derivationPath []uint32, address common.Address, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
-	// Create the transaction initiation message
-	data := tx.Data()
-	length := uint32(len(data))
-
-	request := &trezor.EthereumSignTx{
-		AddressN:   derivationPath,
-		Nonce:      new(big.Int).SetUint64(tx.Nonce()).Bytes(),
-		GasPrice:   tx.GasPrice().Bytes(),
-		GasLimit:   tx.Gas().Bytes(),
-		Value:      tx.Value().Bytes(),
-		DataLength: &length,
-	}
-	if to := tx.To(); to != nil {
-		request.To = (*to)[:] // Non contract deploy, set recipient explicitly
-	}
-	if length > 1024 { // Send the data chunked if that was requested
-		request.DataInitialChunk, data = data[:1024], data[1024:]
-	} else {
-		request.DataInitialChunk, data = data, nil
-	}
-	if chainID != nil { // EIP-155 transaction, set chain ID explicitly (only 32 bit is supported!?)
-		id := uint32(chainID.Int64())
-		request.ChainId = &id
-	}
-	// Send the initiation message and stream content until a signature is returned
-	response := new(trezor.EthereumTxRequest)
-	if err := w.trezorExchange(request, response); err != nil {
-		return nil, err
-	}
-	for response.DataLength != nil && int(*response.DataLength) <= len(data) {
-		chunk := data[:*response.DataLength]
-		data = data[*response.DataLength:]
-
-		if err := w.trezorExchange(&trezor.EthereumTxAck{DataChunk: chunk}, response); err != nil {
-			return nil, err
-		}
-	}
-	// Extract the Ethereum signature and do a sanity validation
-	if len(response.GetSignatureR()) == 0 || len(response.GetSignatureS()) == 0 || response.GetSignatureV() == 0 {
-		return nil, errors.New("reply lacks signature")
-	}
-	signature := append(append(response.GetSignatureR(), response.GetSignatureS()...), byte(response.GetSignatureV()))
-
-	// Create the correct signer and signature transform based on the chain ID
-	var signer types.Signer
-	if chainID == nil {
-		signer = new(types.HomesteadSigner)
-	} else {
-		signer = types.NewEIP155Signer(chainID)
-		signature[64] = signature[64] - byte(chainID.Uint64()*2+35)
-	}
-	// Inject the final signature into the transaction and sanity check the sender
-	signed, err := tx.WithSignature(signer, signature)
-	if err != nil {
-		return nil, err
-	}
-	sender, err := types.Sender(signer, signed)
-	if err != nil {
-		return nil, err
-	}
-	if sender != address {
-		return nil, fmt.Errorf("signer mismatch: expected %s, got %s", address.Hex(), sender.Hex())
-	}
-	return signed, nil
-}
-
-// trezorExchange performs a data exchange with the Trezor wallet, sending it a
-// message and retrieving the response.
-func (w *trezorWallet) trezorExchange(req proto.Message, res proto.Message) error {
-	// Construct the original message payload to chunk up
-	data, err := proto.Marshal(req)
-	if err != nil {
-		return err
-	}
-	payload := make([]byte, 8+len(data))
-	copy(payload, []byte{0x23, 0x23})
-	binary.BigEndian.PutUint16(payload[2:], trezor.Type(req))
-	binary.BigEndian.PutUint32(payload[4:], uint32(len(data)))
-	copy(payload[8:], data)
-
-	// Stream all the chunks to the device
-	chunk := make([]byte, 64)
-	chunk[0] = 0x3f // Report ID magic number
-
-	for len(payload) > 0 {
-		// Construct the new message to stream, padding with zeroes if needed
-		if len(payload) > 63 {
-			copy(chunk[1:], payload[:63])
-			payload = payload[63:]
-		} else {
-			copy(chunk[1:], payload)
-			copy(chunk[1+len(payload):], make([]byte, 63-len(payload)))
-			payload = nil
-		}
-		// Send over to the device
-		w.log.Trace("Data chunk sent to the Trezor", "chunk", hexutil.Bytes(chunk))
-		if _, err := w.device.Write(chunk); err != nil {
-			return err
-		}
-	}
-	// Stream the reply back from the wallet in 64 byte chunks
-	var (
-		kind  uint16
-		reply []byte
-	)
-	for {
-		// Read the next chunk from the Trezor wallet
-		if _, err := io.ReadFull(w.device, chunk); err != nil {
-			return err
-		}
-		w.log.Trace("Data chunk received from the Trezor", "chunk", hexutil.Bytes(chunk))
-
-		// Make sure the transport header matches
-		if chunk[0] != 0x3f || (len(reply) == 0 && (chunk[1] != 0x23 || chunk[2] != 0x23)) {
-			return errReplyInvalidHeader
-		}
-		// If it's the first chunk, retrieve the reply message type and total message length
-		var payload []byte
-
-		if len(reply) == 0 {
-			kind = binary.BigEndian.Uint16(chunk[3:5])
-			reply = make([]byte, 0, int(binary.BigEndian.Uint32(chunk[5:9])))
-			payload = chunk[9:]
-		} else {
-			payload = chunk[1:]
-		}
-		// Append to the reply and stop when filled up
-		if left := cap(reply) - len(reply); left > len(payload) {
-			reply = append(reply, payload...)
-		} else {
-			reply = append(reply, payload[:left]...)
-			break
-		}
-	}
-	// Try to parse the reply into the requested reply message
-	if kind == uint16(trezor.MessageType_MessageType_Failure) {
-		// Trezor returned a failure, extract and return the message
-		failure := new(trezor.Failure)
-		if err := proto.Unmarshal(reply, failure); err != nil {
-			return err
-		}
-		return errors.New("trezor: " + failure.GetMessage())
-	}
-	if kind == uint16(trezor.MessageType_MessageType_ButtonRequest) {
-		// Trezor is waitinf for user confirmation, ack and wait for the next message
-		return w.trezorExchange(&trezor.ButtonAck{}, res)
-	}
-	if want := trezor.Type(res); kind != want {
-		return fmt.Errorf("trezor: expected reply type %s, got %s", trezor.Name(want), trezor.Name(kind))
-	}
-	return proto.Unmarshal(reply, res)
-}
diff --git a/accounts/usbwallet/usbwallet.go b/accounts/usbwallet/usbwallet.go
deleted file mode 100644
index 3ed471693..000000000
--- a/accounts/usbwallet/usbwallet.go
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright 2017 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-// Package usbwallet implements support for USB hardware wallets.
-package usbwallet
-
-import "time"
-
-// deviceID is a combined vendor/product identifier to uniquely identify a USB
-// hardware device.
-type deviceID struct {
-	Vendor  uint16 // The Vendor identifer
-	Product uint16 // The Product identifier
-}
-
-// Maximum time between wallet health checks to detect USB unplugs.
-const heartbeatCycle = time.Second
-
-// Minimum time to wait between self derivation attempts, even it the user is
-// requesting accounts like crazy.
-const selfDeriveThrottling = time.Second
diff --git a/accounts/usbwallet/wallet.go b/accounts/usbwallet/wallet.go
new file mode 100644
index 000000000..8b3b5a522
--- /dev/null
+++ b/accounts/usbwallet/wallet.go
@@ -0,0 +1,562 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package usbwallet implements support for USB hardware wallets.
+package usbwallet
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"math/big"
+	"sync"
+	"time"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/karalabe/hid"
+)
+
+// Maximum time between wallet health checks to detect USB unplugs.
+const heartbeatCycle = time.Second
+
+// Minimum time to wait between self derivation attempts, even it the user is
+// requesting accounts like crazy.
+const selfDeriveThrottling = time.Second
+
+// driver defines the vendor specific functionality hardware wallets instances
+// must implement to allow using them with the wallet lifecycle management.
+type driver interface {
+	// Status returns a textual status to aid the user in the current state of the
+	// wallet. It also returns an error indicating any failure the wallet might have
+	// encountered.
+	Status() (string, error)
+
+	// Open initializes access to a wallet instance. The passphrase parameter may
+	// or may not be used by the implementation of a particular wallet instance.
+	Open(device io.ReadWriter, passphrase string) error
+
+	// Close releases any resources held by an open wallet instance.
+	Close() error
+
+	// Heartbeat performs a sanity check against the hardware wallet to see if it
+	// is still online and healthy.
+	Heartbeat() error
+
+	// Derive sends a derivation request to the USB device and returns the Ethereum
+	// address located on that path.
+	Derive(path accounts.DerivationPath) (common.Address, error)
+
+	// SignTx sends the transaction to the USB device and waits for the user to confirm
+	// or deny the transaction.
+	SignTx(path accounts.DerivationPath, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error)
+}
+
+// wallet represents the common functionality shared by all USB hardware
+// wallets to prevent reimplementing the same complex maintenance mechanisms
+// for different vendors.
+type wallet struct {
+	hub    *Hub          // USB hub scanning
+	driver driver        // Hardware implementation of the low level device operations
+	url    *accounts.URL // Textual URL uniquely identifying this wallet
+
+	info   hid.DeviceInfo // Known USB device infos about the wallet
+	device *hid.Device    // USB device advertising itself as a hardware wallet
+
+	accounts []accounts.Account                         // List of derive accounts pinned on the hardware wallet
+	paths    map[common.Address]accounts.DerivationPath // Known derivation paths for signing operations
+
+	deriveNextPath accounts.DerivationPath   // Next derivation path for account auto-discovery
+	deriveNextAddr common.Address            // Next derived account address for auto-discovery
+	deriveChain    ethereum.ChainStateReader // Blockchain state reader to discover used account with
+	deriveReq      chan chan struct{}        // Channel to request a self-derivation on
+	deriveQuit     chan chan error           // Channel to terminate the self-deriver with
+
+	healthQuit chan chan error
+
+	// Locking a hardware wallet is a bit special. Since hardware devices are lower
+	// performing, any communication with them might take a non negligible amount of
+	// time. Worse still, waiting for user confirmation can take arbitrarily long,
+	// but exclusive communication must be upheld during. Locking the entire wallet
+	// in the mean time however would stall any parts of the system that don't want
+	// to communicate, just read some state (e.g. list the accounts).
+	//
+	// As such, a hardware wallet needs two locks to function correctly. A state
+	// lock can be used to protect the wallet's software-side internal state, which
+	// must not be held exlusively during hardware communication. A communication
+	// lock can be used to achieve exclusive access to the device itself, this one
+	// however should allow "skipping" waiting for operations that might want to
+	// use the device, but can live without too (e.g. account self-derivation).
+	//
+	// Since we have two locks, it's important to know how to properly use them:
+	//   - Communication requires the `device` to not change, so obtaining the
+	//     commsLock should be done after having a stateLock.
+	//   - Communication must not disable read access to the wallet state, so it
+	//     must only ever hold a *read* lock to stateLock.
+	commsLock chan struct{} // Mutex (buf=1) for the USB comms without keeping the state locked
+	stateLock sync.RWMutex  // Protects read and write access to the wallet struct fields
+
+	log log.Logger // Contextual logger to tag the base with its id
+}
+
+// URL implements accounts.Wallet, returning the URL of the USB hardware device.
+func (w *wallet) URL() accounts.URL {
+	return *w.url // Immutable, no need for a lock
+}
+
+// Status implements accounts.Wallet, returning a custom status message from the
+// underlying vendor-specific hardware wallet implementation.
+func (w *wallet) Status() (string, error) {
+	w.stateLock.RLock() // No device communication, state lock is enough
+	defer w.stateLock.RUnlock()
+
+	status, failure := w.driver.Status()
+	if w.device == nil {
+		return "Closed", failure
+	}
+	return status, failure
+}
+
+// Open implements accounts.Wallet, attempting to open a USB connection to the
+// hardware wallet.
+func (w *wallet) Open(passphrase string) error {
+	w.stateLock.Lock() // State lock is enough since there's no connection yet at this point
+	defer w.stateLock.Unlock()
+
+	// If the device was already opened once, refuse to try again
+	if w.paths != nil {
+		return accounts.ErrWalletAlreadyOpen
+	}
+	// Make sure the actual device connection is done only once
+	if w.device == nil {
+		device, err := w.info.Open()
+		if err != nil {
+			return err
+		}
+		w.device = device
+		w.commsLock = make(chan struct{}, 1)
+		w.commsLock <- struct{}{} // Enable lock
+	}
+	// Delegate device initialization to the underlying driver
+	if err := w.driver.Open(w.device, passphrase); err != nil {
+		return err
+	}
+	// Connection successful, start life-cycle management
+	w.paths = make(map[common.Address]accounts.DerivationPath)
+
+	w.deriveReq = make(chan chan struct{})
+	w.deriveQuit = make(chan chan error)
+	w.healthQuit = make(chan chan error)
+
+	go w.heartbeat()
+	go w.selfDerive()
+
+	// Notify anyone listening for wallet events that a new device is accessible
+	go w.hub.updateFeed.Send(accounts.WalletEvent{Wallet: w, Kind: accounts.WalletOpened})
+
+	return nil
+}
+
+// heartbeat is a health check loop for the USB wallets to periodically verify
+// whether they are still present or if they malfunctioned.
+func (w *wallet) heartbeat() {
+	w.log.Debug("USB wallet health-check started")
+	defer w.log.Debug("USB wallet health-check stopped")
+
+	// Execute heartbeat checks until termination or error
+	var (
+		errc chan error
+		err  error
+	)
+	for errc == nil && err == nil {
+		// Wait until termination is requested or the heartbeat cycle arrives
+		select {
+		case errc = <-w.healthQuit:
+			// Termination requested
+			continue
+		case <-time.After(heartbeatCycle):
+			// Heartbeat time
+		}
+		// Execute a tiny data exchange to see responsiveness
+		w.stateLock.RLock()
+		if w.device == nil {
+			// Terminated while waiting for the lock
+			w.stateLock.RUnlock()
+			continue
+		}
+		<-w.commsLock // Don't lock state while resolving version
+		err = w.driver.Heartbeat()
+		w.commsLock <- struct{}{}
+		w.stateLock.RUnlock()
+
+		if err != nil {
+			w.stateLock.Lock() // Lock state to tear the wallet down
+			w.close()
+			w.stateLock.Unlock()
+		}
+		// Ignore non hardware related errors
+		err = nil
+	}
+	// In case of error, wait for termination
+	if err != nil {
+		w.log.Debug("USB wallet health-check failed", "err", err)
+		errc = <-w.healthQuit
+	}
+	errc <- err
+}
+
+// Close implements accounts.Wallet, closing the USB connection to the device.
+func (w *wallet) Close() error {
+	// Ensure the wallet was opened
+	w.stateLock.RLock()
+	hQuit, dQuit := w.healthQuit, w.deriveQuit
+	w.stateLock.RUnlock()
+
+	// Terminate the health checks
+	var herr error
+	if hQuit != nil {
+		errc := make(chan error)
+		hQuit <- errc
+		herr = <-errc // Save for later, we *must* close the USB
+	}
+	// Terminate the self-derivations
+	var derr error
+	if dQuit != nil {
+		errc := make(chan error)
+		dQuit <- errc
+		derr = <-errc // Save for later, we *must* close the USB
+	}
+	// Terminate the device connection
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	w.healthQuit = nil
+	w.deriveQuit = nil
+	w.deriveReq = nil
+
+	if err := w.close(); err != nil {
+		return err
+	}
+	if herr != nil {
+		return herr
+	}
+	return derr
+}
+
+// close is the internal wallet closer that terminates the USB connection and
+// resets all the fields to their defaults.
+//
+// Note, close assumes the state lock is held!
+func (w *wallet) close() error {
+	// Allow duplicate closes, especially for health-check failures
+	if w.device == nil {
+		return nil
+	}
+	// Close the device, clear everything, then return
+	w.device.Close()
+	w.device = nil
+
+	w.accounts, w.paths = nil, nil
+	w.driver.Close()
+
+	return nil
+}
+
+// Accounts implements accounts.Wallet, returning the list of accounts pinned to
+// the USB hardware wallet. If self-derivation was enabled, the account list is
+// periodically expanded based on current chain state.
+func (w *wallet) Accounts() []accounts.Account {
+	// Attempt self-derivation if it's running
+	reqc := make(chan struct{}, 1)
+	select {
+	case w.deriveReq <- reqc:
+		// Self-derivation request accepted, wait for it
+		<-reqc
+	default:
+		// Self-derivation offline, throttled or busy, skip
+	}
+	// Return whatever account list we ended up with
+	w.stateLock.RLock()
+	defer w.stateLock.RUnlock()
+
+	cpy := make([]accounts.Account, len(w.accounts))
+	copy(cpy, w.accounts)
+	return cpy
+}
+
+// selfDerive is an account derivation loop that upon request attempts to find
+// new non-zero accounts.
+func (w *wallet) selfDerive() {
+	w.log.Debug("USB wallet self-derivation started")
+	defer w.log.Debug("USB wallet self-derivation stopped")
+
+	// Execute self-derivations until termination or error
+	var (
+		reqc chan struct{}
+		errc chan error
+		err  error
+	)
+	for errc == nil && err == nil {
+		// Wait until either derivation or termination is requested
+		select {
+		case errc = <-w.deriveQuit:
+			// Termination requested
+			continue
+		case reqc = <-w.deriveReq:
+			// Account discovery requested
+		}
+		// Derivation needs a chain and device access, skip if either unavailable
+		w.stateLock.RLock()
+		if w.device == nil || w.deriveChain == nil {
+			w.stateLock.RUnlock()
+			reqc <- struct{}{}
+			continue
+		}
+		select {
+		case <-w.commsLock:
+		default:
+			w.stateLock.RUnlock()
+			reqc <- struct{}{}
+			continue
+		}
+		// Device lock obtained, derive the next batch of accounts
+		var (
+			accs  []accounts.Account
+			paths []accounts.DerivationPath
+
+			nextAddr = w.deriveNextAddr
+			nextPath = w.deriveNextPath
+
+			context = context.Background()
+		)
+		for empty := false; !empty; {
+			// Retrieve the next derived Ethereum account
+			if nextAddr == (common.Address{}) {
+				if nextAddr, err = w.driver.Derive(nextPath); err != nil {
+					w.log.Warn("USB wallet account derivation failed", "err", err)
+					break
+				}
+			}
+			// Check the account's status against the current chain state
+			var (
+				balance *big.Int
+				nonce   uint64
+			)
+			balance, err = w.deriveChain.BalanceAt(context, nextAddr, nil)
+			if err != nil {
+				w.log.Warn("USB wallet balance retrieval failed", "err", err)
+				break
+			}
+			nonce, err = w.deriveChain.NonceAt(context, nextAddr, nil)
+			if err != nil {
+				w.log.Warn("USB wallet nonce retrieval failed", "err", err)
+				break
+			}
+			// If the next account is empty, stop self-derivation, but add it nonetheless
+			if balance.Sign() == 0 && nonce == 0 {
+				empty = true
+			}
+			// We've just self-derived a new account, start tracking it locally
+			path := make(accounts.DerivationPath, len(nextPath))
+			copy(path[:], nextPath[:])
+			paths = append(paths, path)
+
+			account := accounts.Account{
+				Address: nextAddr,
+				URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
+			}
+			accs = append(accs, account)
+
+			// Display a log message to the user for new (or previously empty accounts)
+			if _, known := w.paths[nextAddr]; !known || (!empty && nextAddr == w.deriveNextAddr) {
+				w.log.Info("USB wallet discovered new account", "address", nextAddr, "path", path, "balance", balance, "nonce", nonce)
+			}
+			// Fetch the next potential account
+			if !empty {
+				nextAddr = common.Address{}
+				nextPath[len(nextPath)-1]++
+			}
+		}
+		// Self derivation complete, release device lock
+		w.commsLock <- struct{}{}
+		w.stateLock.RUnlock()
+
+		// Insert any accounts successfully derived
+		w.stateLock.Lock()
+		for i := 0; i < len(accs); i++ {
+			if _, ok := w.paths[accs[i].Address]; !ok {
+				w.accounts = append(w.accounts, accs[i])
+				w.paths[accs[i].Address] = paths[i]
+			}
+		}
+		// Shift the self-derivation forward
+		// TODO(karalabe): don't overwrite changes from wallet.SelfDerive
+		w.deriveNextAddr = nextAddr
+		w.deriveNextPath = nextPath
+		w.stateLock.Unlock()
+
+		// Notify the user of termination and loop after a bit of time (to avoid trashing)
+		reqc <- struct{}{}
+		if err == nil {
+			select {
+			case errc = <-w.deriveQuit:
+				// Termination requested, abort
+			case <-time.After(selfDeriveThrottling):
+				// Waited enough, willing to self-derive again
+			}
+		}
+	}
+	// In case of error, wait for termination
+	if err != nil {
+		w.log.Debug("USB wallet self-derivation failed", "err", err)
+		errc = <-w.deriveQuit
+	}
+	errc <- err
+}
+
+// Contains implements accounts.Wallet, returning whether a particular account is
+// or is not pinned into this wallet instance. Although we could attempt to resolve
+// unpinned accounts, that would be an non-negligible hardware operation.
+func (w *wallet) Contains(account accounts.Account) bool {
+	w.stateLock.RLock()
+	defer w.stateLock.RUnlock()
+
+	_, exists := w.paths[account.Address]
+	return exists
+}
+
+// Derive implements accounts.Wallet, deriving a new account at the specific
+// derivation path. If pin is set to true, the account will be added to the list
+// of tracked accounts.
+func (w *wallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
+	// Try to derive the actual account and update its URL if successful
+	w.stateLock.RLock() // Avoid device disappearing during derivation
+
+	if w.device == nil {
+		w.stateLock.RUnlock()
+		return accounts.Account{}, accounts.ErrWalletClosed
+	}
+	<-w.commsLock // Avoid concurrent hardware access
+	address, err := w.driver.Derive(path)
+	w.commsLock <- struct{}{}
+
+	w.stateLock.RUnlock()
+
+	// If an error occurred or no pinning was requested, return
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	account := accounts.Account{
+		Address: address,
+		URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
+	}
+	if !pin {
+		return account, nil
+	}
+	// Pinning needs to modify the state
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	if _, ok := w.paths[address]; !ok {
+		w.accounts = append(w.accounts, account)
+		w.paths[address] = path
+	}
+	return account, nil
+}
+
+// SelfDerive implements accounts.Wallet, trying to discover accounts that the
+// user used previously (based on the chain state), but ones that he/she did not
+// explicitly pin to the wallet manually. To avoid chain head monitoring, self
+// derivation only runs during account listing (and even then throttled).
+func (w *wallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	w.deriveNextPath = make(accounts.DerivationPath, len(base))
+	copy(w.deriveNextPath[:], base[:])
+
+	w.deriveNextAddr = common.Address{}
+	w.deriveChain = chain
+}
+
+// SignHash implements accounts.Wallet, however signing arbitrary data is not
+// supported for hardware wallets, so this method will always return an error.
+func (w *wallet) SignHash(account accounts.Account, hash []byte) ([]byte, error) {
+	return nil, accounts.ErrNotSupported
+}
+
+// SignTx implements accounts.Wallet. It sends the transaction over to the Ledger
+// wallet to request a confirmation from the user. It returns either the signed
+// transaction or a failure if the user denied the transaction.
+//
+// Note, if the version of the Ethereum application running on the Ledger wallet is
+// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
+// will be returned opposed to silently signing in Homestead mode.
+func (w *wallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	w.stateLock.RLock() // Comms have own mutex, this is for the state fields
+	defer w.stateLock.RUnlock()
+
+	// If the wallet is closed, abort
+	if w.device == nil {
+		return nil, accounts.ErrWalletClosed
+	}
+	// Make sure the requested account is contained within
+	path, ok := w.paths[account.Address]
+	if !ok {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// All infos gathered and metadata checks out, request signing
+	<-w.commsLock
+	defer func() { w.commsLock <- struct{}{} }()
+
+	// Ensure the device isn't screwed with while user confirmation is pending
+	// TODO(karalabe): remove if hotplug lands on Windows
+	w.hub.commsLock.Lock()
+	w.hub.commsPend++
+	w.hub.commsLock.Unlock()
+
+	defer func() {
+		w.hub.commsLock.Lock()
+		w.hub.commsPend--
+		w.hub.commsLock.Unlock()
+	}()
+	// Sign the transaction and verify the sender to avoid hardware fault surprises
+	sender, signed, err := w.driver.SignTx(path, tx, chainID)
+	if err != nil {
+		return nil, err
+	}
+	if sender != account.Address {
+		return nil, fmt.Errorf("signer mismatch: expected %s, got %s", account.Address.Hex(), sender.Hex())
+	}
+	return signed, nil
+}
+
+// SignHashWithPassphrase implements accounts.Wallet, however signing arbitrary
+// data is not supported for Ledger wallets, so this method will always return
+// an error.
+func (w *wallet) SignHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
+	return w.SignHash(account, hash)
+}
+
+// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
+// transaction with the given account using passphrase as extra authentication.
+// Since USB wallets don't rely on passphrases, these are silently ignored.
+func (w *wallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	return w.SignTx(account, tx, chainID)
+}
diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index 257cb2231..34d1d8406 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -251,7 +251,9 @@ func startNode(ctx *cli.Context, stack *node.Node) {
 					log.Warn("New wallet appeared, failed to open", "url", event.Wallet.URL(), "err", err)
 				}
 			case accounts.WalletOpened:
-				log.Info("New wallet appeared", "url", event.Wallet.URL(), "status", event.Wallet.Status())
+				status, _ := event.Wallet.Status()
+				log.Info("New wallet appeared", "url", event.Wallet.URL(), "status", status)
+
 				if event.Wallet.URL().Scheme == "ledger" {
 					event.Wallet.SelfDerive(accounts.DefaultLedgerBaseDerivationPath, stateReader)
 				} else {
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 6b9c151cf..c3924b93a 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -230,18 +230,25 @@ func (s *PrivateAccountAPI) ListAccounts() []common.Address {
 type rawWallet struct {
 	URL      string             `json:"url"`
 	Status   string             `json:"status"`
-	Accounts []accounts.Account `json:"accounts"`
+	Failure  string             `json:"failure,omitempty"`
+	Accounts []accounts.Account `json:"accounts,omitempty"`
 }
 
 // ListWallets will return a list of wallets this node manages.
 func (s *PrivateAccountAPI) ListWallets() []rawWallet {
 	wallets := make([]rawWallet, 0) // return [] instead of nil if empty
 	for _, wallet := range s.am.Wallets() {
-		wallets = append(wallets, rawWallet{
+		status, failure := wallet.Status()
+
+		raw := rawWallet{
 			URL:      wallet.URL().String(),
-			Status:   wallet.Status(),
+			Status:   status,
 			Accounts: wallet.Accounts(),
-		})
+		}
+		if failure != nil {
+			raw.Failure = failure.Error()
+		}
+		wallets = append(wallets, raw)
 	}
 	return wallets
 }