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channeldb+lnwallet: replace elkrem with shachain

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In this commit the initial implementation of revocation hash
generation 'elkrem' was replaced with 'shachain' Rusty Russel
implementation which currently enshrined in the spec. This alghoritm has
the same asymptotic characteristics but has more complex scheme
to determine wish hash we can drop and what needs to be stored
in order to be able to achive full compression.
This commit is contained in:
Andrey Samokhvalov authored and Olaoluwa Osuntokun committed 2017-02-22 16:49:29 -08:00
1 parent b40afeaa08
commit f86557c3e4
11 files changed
+206 -573
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lnwallet/wallet.go
+40 -42
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@@ -11,10 +11,10 @@ import (
"github.com/davecgh/go-spew/spew"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/elkrem"
"github.com/roasbeef/btcd/chaincfg"
"github.com/roasbeef/btcutil/hdkeychain"
"github.com/lightningnetwork/lnd/shachain"
"github.com/roasbeef/btcd/btcec"
"github.com/roasbeef/btcd/txscript"
"github.com/roasbeef/btcd/wire"
@@ -27,9 +27,9 @@ const (
// outside word.
msgBufferSize = 100
// elkremRootIndex is the top level HD key index from which secrets
// used to generate elkrem roots should be derived from.
elkremRootIndex = hdkeychain.HardenedKeyStart + 1
// revocationRootIndex is the top level HD key index from which secrets
// used to generate producer roots should be derived from.
revocationRootIndex = hdkeychain.HardenedKeyStart + 1
// identityKeyIndex is the top level HD key index which is used to
// generate/rotate identity keys.
@@ -42,7 +42,6 @@ const (
)
var (
// Namespace bucket keys.
lightningNamespaceKey = []byte("ln-wallet")
waddrmgrNamespaceKey = []byte("waddrmgr")
@@ -757,11 +756,11 @@ func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) {
// Initialize an empty sha-chain for them, tracking the current pending
// revocation hash (we don't yet know the preimage so we can't add it
// to the chain).
e := &elkrem.ElkremReceiver{}
pendingReservation.partialState.RemoteElkrem = e
s := shachain.NewRevocationStore()
pendingReservation.partialState.RevocationStore = s
pendingReservation.partialState.TheirCurrentRevocation = theirContribution.RevocationKey
masterElkremRoot, err := l.deriveMasterElkremRoot()
masterElkremRoot, err := l.deriveMasterRevocationRoot()
if err != nil {
req.err <- err
return
@@ -769,12 +768,11 @@ func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) {
// Now that we have their commitment key, we can create the revocation
// key for the first version of our commitment transaction. To do so,
// we'll first create our elkrem root, then grab the first pre-iamge
// from it.
elkremRoot := deriveElkremRoot(masterElkremRoot, ourKey, theirKey)
elkremSender := elkrem.NewElkremSender(elkremRoot)
pendingReservation.partialState.LocalElkrem = elkremSender
firstPreimage, err := elkremSender.AtIndex(0)
// we'll first create our root, then produce the first pre-image.
root := deriveRevocationRoot(masterElkremRoot, ourKey, theirKey)
producer := shachain.NewRevocationProducer(root)
pendingReservation.partialState.RevocationProducer = producer
firstPreimage, err := producer.AtIndex(0)
if err != nil {
req.err <- err
return
@@ -812,7 +810,7 @@ func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) {
// TODO(roasbeef): define obsfucator scheme for dual funder
var stateObsfucator [StateHintSize]byte
if pendingReservation.partialState.IsInitiator {
stateObsfucator, err = deriveStateHintObsfucator(elkremSender)
stateObsfucator, err = deriveStateHintObfuscator(producer)
if err != nil {
req.err <- err
return
@@ -902,7 +900,7 @@ func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg
}
pendingReservation.partialState.FundingWitnessScript = witnessScript
masterElkremRoot, err := l.deriveMasterElkremRoot()
masterElkremRoot, err := l.deriveMasterRevocationRoot()
if err != nil {
req.err <- err
return
@@ -910,22 +908,22 @@ func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg
// Now that we know their commitment key, we can create the revocation
// key for our version of the initial commitment transaction.
elkremRoot := deriveElkremRoot(masterElkremRoot, ourKey, theirKey)
elkremSender := elkrem.NewElkremSender(elkremRoot)
firstPreimage, err := elkremSender.AtIndex(0)
root := deriveRevocationRoot(masterElkremRoot, ourKey, theirKey)
producer := shachain.NewRevocationProducer(root)
firstPreimage, err := producer.AtIndex(0)
if err != nil {
req.err <- err
return
}
pendingReservation.partialState.LocalElkrem = elkremSender
pendingReservation.partialState.RevocationProducer = producer
theirCommitKey := theirContribution.CommitKey
ourRevokeKey := DeriveRevocationPubkey(theirCommitKey, firstPreimage[:])
// Initialize an empty sha-chain for them, tracking the current pending
// revocation hash (we don't yet know the preimage so we can't add it
// to the chain).
remoteElkrem := &elkrem.ElkremReceiver{}
pendingReservation.partialState.RemoteElkrem = remoteElkrem
remotePreimageStore := shachain.NewRevocationStore()
pendingReservation.partialState.RevocationStore = remotePreimageStore
// Record the counterpaty's remaining contributions to the channel,
// converting their delivery address into a public key script.
@@ -1379,11 +1377,11 @@ func (l *LightningWallet) selectCoinsAndChange(feeRate uint64, amt btcutil.Amoun
return nil
}
// deriveMasterElkremRoot derives the private key which serves as the master
// elkrem root. This master secret is used as the secret input to a HKDF to
// generate elkrem secrets based on random, but public data.
func (l *LightningWallet) deriveMasterElkremRoot() (*btcec.PrivateKey, error) {
masterElkremRoot, err := l.rootKey.Child(elkremRootIndex)
// deriveMasterRevocationRoot derives the private key which serves as the master
// producer root. This master secret is used as the secret input to a HKDF to
// generate revocation secrets based on random, but public data.
func (l *LightningWallet) deriveMasterRevocationRoot() (*btcec.PrivateKey, error) {
masterElkremRoot, err := l.rootKey.Child(revocationRootIndex)
if err != nil {
return nil, err
}
@@ -1391,34 +1389,34 @@ func (l *LightningWallet) deriveMasterElkremRoot() (*btcec.PrivateKey, error) {
return masterElkremRoot.ECPrivKey()
}
// deriveStateHintObsfucator derives the bytes to be used for obsfucatating the
// state hints from the elkerem root to be used for a new channel. The
// obsfucator is generated by performing an additional sha256 hash of the first
// child derived from the elkrem root. The leading 4 bytes are used for the
// obsfucator.
func deriveStateHintObsfucator(elkremRoot *elkrem.ElkremSender) ([StateHintSize]byte, error) {
var obsfucator [StateHintSize]byte
// deriveStateHintObfuscator derives the bytes to be used for obfuscating the
// state hints from the root to be used for a new channel. The
// obfuscator is generated by performing an additional sha256 hash of the first
// child derived from the revocation root. The leading 4 bytes are used for the
// obfuscator.
func deriveStateHintObfuscator(producer shachain.Producer) ([StateHintSize]byte, error) {
var obfuscator [StateHintSize]byte
firstChild, err := elkremRoot.AtIndex(0)
firstChild, err := producer.AtIndex(0)
if err != nil {
return obsfucator, err
return obfuscator, err
}
grandChild := fastsha256.Sum256(firstChild[:])
copy(obsfucator[:], grandChild[:])
copy(obfuscator[:], grandChild[:])
return obsfucator, nil
return obfuscator, nil
}
// initStateHints properly sets the obsfucated state hints on both commitment
// transactions using the passed obsfucator.
func initStateHints(commit1, commit2 *wire.MsgTx,
obsfucator [StateHintSize]byte) error {
obfuscator [StateHintSize]byte) error {
if err := SetStateNumHint(commit1, 0, obsfucator); err != nil {
if err := SetStateNumHint(commit1, 0, obfuscator); err != nil {
return err
}
if err := SetStateNumHint(commit2, 0, obsfucator); err != nil {
if err := SetStateNumHint(commit2, 0, obfuscator); err != nil {
return err
}
@@ -1426,7 +1424,7 @@ func initStateHints(commit1, commit2 *wire.MsgTx,
}
// selectInputs selects a slice of inputs necessary to meet the specified
// selection amount. If input selection is unable to suceed to to insuffcient
// selection amount. If input selection is unable to succeed to to insufficient
// funds, a non-nil error is returned. Additionally, the total amount of the
// selected coins are returned in order for the caller to properly handle
// change+fees.