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multi: add new tapscript root option to GenTaprootFundingScript

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This'll allow us to create a funding output that uses musig2, but uses a tapscript tweak rather than a normal BIP 86 tweak.
This commit is contained in:
Olaoluwa Osuntokun
2024-03-13 10:46:33 -04:00
committed by Oliver Gugger
parent edf959d39f
commit 2c56b3120a
8 changed files with 36 additions and 16 deletions
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24
input/script_utils.go
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@@ -11,8 +11,10 @@ import (
"github.com/btcsuite/btcd/btcec/v2/schnorr"
"github.com/btcsuite/btcd/btcec/v2/schnorr/musig2"
"github.com/btcsuite/btcd/btcutil"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/lightningnetwork/lnd/fn"
"github.com/lightningnetwork/lnd/lntypes"
"github.com/lightningnetwork/lnd/lnutils"
"golang.org/x/crypto/ripemd160"
@@ -199,26 +201,30 @@ func GenFundingPkScript(aPub, bPub []byte, amt int64) ([]byte, *wire.TxOut, erro
}
// GenTaprootFundingScript constructs the taproot-native funding output that
// uses musig2 to create a single aggregated key to anchor the channel.
// uses MuSig2 to create a single aggregated key to anchor the channel.
func GenTaprootFundingScript(aPub, bPub *btcec.PublicKey,
amt int64) ([]byte, *wire.TxOut, error) {
amt int64, tapscriptRoot fn.Option[chainhash.Hash]) ([]byte,
*wire.TxOut, error) {
muSig2Opt := musig2.WithBIP86KeyTweak()
tapscriptRoot.WhenSome(func(scriptRoot chainhash.Hash) {
muSig2Opt = musig2.WithTaprootKeyTweak(scriptRoot[:])
})
// Similar to the existing p2wsh funding script, we'll always make sure
// we sort the keys before any major operations. In order to ensure
// that there's no other way this output can be spent, we'll use a BIP
// 86 tweak here during aggregation.
//
// TODO(roasbeef): revisit if BIP 86 is needed here?
// 86 tweak here during aggregation, unless the user has explicitly
// specified a tapscript root.
combinedKey, _, _, err := musig2.AggregateKeys(
[]*btcec.PublicKey{aPub, bPub}, true,
musig2.WithBIP86KeyTweak(),
[]*btcec.PublicKey{aPub, bPub}, true, muSig2Opt,
)
if err != nil {
return nil, nil, fmt.Errorf("unable to combine keys: %w", err)
}
// Now that we have the combined key, we can create a taproot pkScript
// from this, and then make the txout given the amount.
// from this, and then make the txOut given the amount.
pkScript, err := PayToTaprootScript(combinedKey.FinalKey)
if err != nil {
return nil, nil, fmt.Errorf("unable to make taproot "+
@@ -228,7 +234,7 @@ func GenTaprootFundingScript(aPub, bPub *btcec.PublicKey,
txOut := wire.NewTxOut(amt, pkScript)
// For the "witness program" we just return the raw pkScript since the
// output we create can _only_ be spent with a musig2 signature.
// output we create can _only_ be spent with a MuSig2 signature.
return pkScript, txOut, nil
}