This update the wallet to implement the new single funder workflow
which uses revocation keys rather than revocation hashes for the
commitment transactions.
The derivation is current bed on an HKDF invocation using our private
key as the secret, and the node’s channel multi-sig key as the salt.
This scheme allows us to derive the key on the fly given data known to
only us and the remote node.
The current derivation is just a place-holder and will be re-visited at
a later time.
With this commit, the reservation workflow for the single funder use
case is now aware of the usage of revocation keys.
The changes are relatively minor:
* contributions now have RevocationKeys instead of RevocationHashes
* CompleteReservationSingle now takes the initiators revocation key
This commit implements the “send coins” RPC request which was
introduced at both the lnrpc and command line level in a prior commit.
A small refactoring has taken place w.r.t to sendmany+sendcoins in
order to eliminate some code duplication.
This commit updates the previous HTLC and commitment scripts to their
current latest evolution.
The HTLC scripts have been optimized for space savings, the
functionality itself has remained relatively unchanged. A trade off was
made to add additional bytes into the sigScript in order to avoid
extraneous CHECKSIG’s. The rationale is that an extra 1-2 bytes in the
sigScript to guide execution, are worthwhile since they’re in the
witness, and witness data may be pruned in the near future.
The primary change is within the commitment transaction itself. Instead
of using revocation hashes, we now use signature based revocation. This
saves space in the Script, and optimizes away an extra hashing
operation. Elkrem/shachain is still used but, we now use the pre-images
to homomorphically derive a public key which the other party will be
able to sign with, once we disclose the pre-image itself.
Finally, we have switched to using SHA-256 everywhere uniformly for
both revocation hashes, and payment hashes. The rationale is that the
output of ripemd160 is too small for modern security margins, and that
other coins/chains are more likely to have SHA-256 implemented, than
ripemd160.
A set of tests has also been included which contain (mostly) exhaustive
tests of all possible redemption paths for both commitment and HTLC.
This unifies some inconstancies across the code-base with hashes being
32 vs 20 bytes. All hashes, whether payment or revocation are now
uniformly 32 bytes everywhere. As a result, only OP_SHA256 will be used
within commitment and HTLC scripts. The rationale for using sha256
instead of hash160 for the HTLC payment pre-image is that alternative
chains are more likely to have sha256 implemented, rather than
ripemd160.
A forthcoming commit will update the current commitment, and HTLC
scripts.
This commit introduces the fundingManger which is used as a bridge
between the wallet’s internal ‘ChannelReservation’ workflow, and the
wire protocol’s funding messages.
The funding manger is responsible for progressing the workflow, and
communicating any errors generated during the workflow back to the
source peer.
This commit adds additional test cases to test both cases (initiator vs
responder) for a single funder channel workflow. Additionally, the
previous dual funder tests have been extended in order to detect proper
funding channel broadcast, and the ChainNotifier’s role in notifying
upstream callers that a funding transaction has been embedded in the
chain at a sufficient depth.
At this point the tests certainly need to be cleaned up. bobNode should
be replaced with a second instance of the wallet modeling a remote
peer.
This commit modifies the existing workflow to add additional paths to
be used when on the responding side of a single funder workflow.
Additionally, several bugs encountered within the existing dual funder
workflow logic have been fixed, and modified to account for the wallet
being on the igniting side of a single funder workflow.
The previous logic incorrectly assumed the returned address was already
a p2wkh address. Instead, a p2sh address was returned. So we now
correctly craft both the sigScript and witness stack for a nested p2sh
spend.
This is required since for single funder channels, we don’t contribute
any funds so we don’t need to select any change or coins for input into
the funding transaction.
This commit adds 3 methods to lnwallet.ChannelReservation intended to
facilitating a single funder channel workflow between two nodes. A
single funder workflow is characterized as the initiator committing all
the funds to a channel, with the responder only providing public keys,
and a revocation hash.
The workflow remains the same for the initiator of the funding
transaction, however for the responder, the following methods are
instead called in order:
* .ProcessSingleConribution()
* .CompleteSingleContribution()
* .FinalizeReservation()
These methods are required for the responder as they are never able to
construct the full funding transaction, and only receive the out point
of the funding transaction once available.
A cooperative closure of a LightningChannel proceeds in two steps.
First, the party who wishes to close the channel sends a signature for
the closing transaction. Next, the responder reconstructs the closing
transaction identically as the initiator did using a canonical
input/output ordering, and the currently settled balance within the
channel. At this point, the responder then broadcasts the closure
transaction. It is the responsibility of the initiator to watch for
this transaction broadcast within the network to clean up any resources
they committed to the active channel.
Only nested p2sh or pure witness outputs are used when selecting coins
for inputs to a funding transaction.
The funding transaction output now uses p2wsh rather than regular p2sh.
All tests have been updated accordingly.
This method has been added in order to allow lnd to collect eligible
unspent witness programs outputs from the wallet controller for use as
inputs to the funding transaction.
Additionally, the change address functions now also specify whether the
generated change address should be payable to a witness program or not.
The WalletController will serve as a layer of separation between “base”
Bitcoin wallet logic, and the higher level Lightning Network logic. As
a result LightningWallet will no behave as an overly wallet, relying on
the lower wallet for basic services such as new address, signing etc.
Within this higher level lies the awareness of channel types, chain
monitoring, HTLCs, and so on.
* Previously, if the call to SetUp(..) returned an error, then the test
harness would fail to stop the running bcd process, and clean up the
test directories. This would cause any subsequent tests to fail. This
commit remedies this scenario.
Allows us to remove a lot of duplicated code pertaining to wallet
setup. We also gain hooks into the wallet to trigger callbacks once the
wallet is created/opened.
Instead of creating “fake” utxos for bob, and alice. We now employ a
dedicated mining node to hand out utxos, and generate blocks with hand
picked transactions.
Olaoluwa Osuntokun
Tadge Dryja
mkl