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input: add TaprootCommitScriptToSelf for taproot to self script

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Olaoluwa Osuntokun 2023-01-16 20:02:18 -08:00
parent 9d0c04bfa2
commit 5f81919284
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1 changed files with 57 additions and 0 deletions
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57
input/script_utils.go
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@ -6,6 +6,7 @@ import (
"fmt"
"github.com/btcsuite/btcd/btcec/v2"
"github.com/btcsuite/btcd/btcec/v2/schnorr"
"github.com/btcsuite/btcd/btcec/v2/schnorr/musig2"
"github.com/btcsuite/btcd/btcutil"
"github.com/btcsuite/btcd/txscript"
@ -1080,6 +1081,62 @@ func CommitScriptToSelf(csvTimeout uint32, selfKey, revokeKey *btcec.PublicKey)
return builder.Script()
}
// TaprootCommitScriptToSelf creates the taproot witness program that commits
// to the revocation (keyspend) and delay path (script path) in a single
// taproot output key.
//
// For the delay path we have the following tapscript leaf script:
//
// <local_delayedpubkey> OP_CHECKSIG
// <to_self_delay> OP_CHECKSEQUENCEVERIFY OP_DROP
//
// This can then be spent with just:
//
// <local_delayedsig> <to_delay_script> <delay_control_block>
//
// Where the to_delay_script is listed above, and the delay_control_block
// computed as:
//
// delay_control_block = (output_key_y_parity | 0xc0) || revocationpubkey
//
// The revocation key spend path will simply present a valid signature with the
// witness being just:
//
// <revocation_sig>
func TaprootCommitScriptToSelf(csvTimeout uint32,
selfKey, revokeKey *btcec.PublicKey) (*btcec.PublicKey, error) {
// First, we'll need to construct the tapLeaf that'll be our delay CSV
// clause.
//
// TODO(roasbeef): extract into diff func
builder := txscript.NewScriptBuilder()
builder.AddData(schnorr.SerializePubKey(selfKey))
builder.AddOp(txscript.OP_CHECKSIG)
builder.AddInt64(int64(csvTimeout))
builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
builder.AddOp(txscript.OP_DROP)
delayScript, err := builder.Script()
if err != nil {
return nil, err
}
// With the delay script computed, we'll now create a tapscript tree
// with a single leaf, and then obtain a root from that.
tapLeaf := txscript.NewBaseTapLeaf(delayScript)
tapScriptTree := txscript.AssembleTaprootScriptTree(tapLeaf)
tapScriptRoot := tapScriptTree.RootNode.TapHash()
// Now that we have our root, we can arrive at the final output script
// by tweaking the internal key with this root.
toLocalOutputKey := txscript.ComputeTaprootOutputKey(
revokeKey, tapScriptRoot[:],
)
return toLocalOutputKey, nil
}
// LeaseCommitScriptToSelf constructs the public key script for the output on the
// commitment transaction paying to the "owner" of said commitment transaction.
// If the other party learns of the preimage to the revocation hash, then they