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fix: lock the force-skip connector to the committee #23

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fix: lock the force-skip connector to the committee #23

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c24f6cc
lock force-skip connector to the committee
Nov 9, 2026
2c76a2c
format prekickoff
Nov 9, 2026
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13 changes: 8 additions & 5 deletions goat/src/connectors/kickoff_connectors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -172,22 +172,25 @@ impl TaprootConnector for KickoffConnector {
}
}

/// Output 0 of the next Pre-Kickoff, spent only by the committee-signed
/// Quick-Challenge or Force-Skip-Kickoff. The operator holds no key to it, so
/// it cannot sweep the output and make those penalties unspendable.
#[derive(Serialize, Deserialize, Eq, PartialEq, Clone)]
pub struct ForceSkipConnector {
pub network: Network,
pub operator_taproot_public_key: XOnlyPublicKey,
pub n_of_n_taproot_public_key: XOnlyPublicKey,
}

impl ForceSkipConnector {
pub fn new(network: Network, operator_taproot_public_key: &XOnlyPublicKey) -> Self {
pub fn new(network: Network, n_of_n_taproot_public_key: &XOnlyPublicKey) -> Self {
ForceSkipConnector {
network,
operator_taproot_public_key: *operator_taproot_public_key,
n_of_n_taproot_public_key: *n_of_n_taproot_public_key,
}
}

fn generate_taproot_leaf_0_script(&self) -> ScriptBuf {
generate_pay_to_pubkey_taproot_script(&self.operator_taproot_public_key)
generate_pay_to_pubkey_taproot_script(&self.n_of_n_taproot_public_key)
}

fn generate_taproot_leaf_0_tx_in(&self, input: &Input) -> TxIn {
Expand All @@ -214,7 +217,7 @@ impl TaprootConnector for ForceSkipConnector {
TaprootBuilder::new()
.add_leaf(0, self.generate_taproot_leaf_0_script())
.expect("Unable to add leaf 0")
.finalize(SECP256K1, self.operator_taproot_public_key)
.finalize(SECP256K1, self.n_of_n_taproot_public_key)
.expect("Unable to finalize taproot")
}

Expand Down
207 changes: 185 additions & 22 deletions goat/src/transactions/prekickoff.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
use bitcoin::{
absolute, consensus, Address, Amount, ScriptBuf, TapSighashType, Transaction, TxIn, TxOut,
};
use musig2::{errors::SigningError, AggNonce, PartialSignature, SecNonce};
use serde::{Deserialize, Serialize};

use crate::{
Expand All @@ -10,10 +11,18 @@ use crate::{
ForceSkipConnector, GuardianConnector, KickoffConnector, PrekickoffConnector,
},
},
contexts::operator::OperatorContext,
contexts::{base::BaseContext, committee::CommitteeContext, operator::OperatorContext},
error::{Error, TransactionError::InsufficientInputAmount},
scripts::p2a_output,
transactions::signing::populate_taproot_input_witness_default,
transactions::{
signing::{
populate_taproot_input_witness_default,
push_taproot_leaf_script_and_control_block_to_witness,
},
signing_musig2::{
generate_taproot_aggregated_signature, generate_taproot_partial_signature,
},
},
};

use super::{base::*, pre_signed::*};
Expand Down Expand Up @@ -266,7 +275,7 @@ impl ForceSkipKickoffTransaction {
input_1,
);

this.pre_sign_and_push(context, kickoff_connector, next_force_skip_connector);
this.pre_sign_and_push(context, kickoff_connector);

this
}
Expand Down Expand Up @@ -325,29 +334,106 @@ impl ForceSkipKickoffTransaction {
);
}

pub fn sign_input_1(
fn sign_input_1_musig2(
&mut self,
context: &CommitteeContext,
sec_nonce: &SecNonce,
agg_nonce: &AggNonce,
) -> Result<PartialSignature, SigningError> {
let input_index = 1;
let sighash_type = TapSighashType::None;
generate_taproot_partial_signature(
context,
self.tx(),
sec_nonce,
agg_nonce,
input_index,
self.prev_outs(),
&self.prev_scripts()[input_index],
sighash_type,
)
}

fn push_input_1_signature(
&mut self,
context: &OperatorContext,
next_force_skip_connector: &ForceSkipConnector,
input_1_sig: bitcoin::taproot::Signature,
) {
let input_index = 1;
pre_sign_taproot_input_default(
self,
let script = self.prev_scripts()[input_index].clone();
let spend_info = next_force_skip_connector.generate_taproot_spend_info();
let tx_mut = self.tx_mut();
tx_mut.input[input_index]
.witness
.push(input_1_sig.serialize());
push_taproot_leaf_script_and_control_block_to_witness(
tx_mut,
input_index,
TapSighashType::None,
next_force_skip_connector.generate_taproot_spend_info(),
&vec![&context.operator_keypair],
&spend_info,
&script,
);
}

pub fn pre_sign(
&mut self,
context: &CommitteeContext,
sec_nonces: &[SecNonce; 1],
agg_nonces: &[AggNonce; 1],
) -> Result<[PartialSignature; 1], SigningError> {
let input_1_sig = self.sign_input_1_musig2(context, &sec_nonces[0], &agg_nonces[0]);
match [input_1_sig]
.into_iter()
.collect::<Result<Vec<PartialSignature>, SigningError>>()
{
Ok(sigs) => Ok(sigs.try_into().unwrap()),
Err(e) => Err(e),
}
}

pub fn aggregate_pre_sigs(
&self,
context: &dyn BaseContext,
partial_signatures: &[Vec<PartialSignature>; 1],
agg_nonces: &[AggNonce; 1],
) -> Result<[bitcoin::taproot::Signature; 1], Error> {
let input_index = 1;
let sig_index = 0;
let sighash_type = TapSighashType::None;
let input_1_sig = match generate_taproot_aggregated_signature(
context,
self.tx(),
&agg_nonces[sig_index],
input_index,
self.prev_outs(),
&self.prev_scripts()[input_index],
sighash_type,
partial_signatures[sig_index].clone(),
) {
Ok(sig) => bitcoin::taproot::Signature {
signature: sig.into(),
sighash_type,
},
Err(_) => return Err(Error::Other("Failed to aggregate signatures")),
};
Ok([input_1_sig])
}

pub fn push_pre_sigs(
&mut self,
next_force_skip_connector: &ForceSkipConnector,
pre_sigs: [bitcoin::taproot::Signature; 1],
) {
self.push_input_1_signature(next_force_skip_connector, pre_sigs[0]);
}

/// Signs input 0. Input 1 spends the force-skip connector and is signed
/// by the committee through `pre_sign`.
pub fn pre_sign_and_push(
&mut self,
context: &OperatorContext,
kickoff_connector: &KickoffConnector,
next_force_skip_connector: &ForceSkipConnector,
) {
self.sign_input_0(context, kickoff_connector);
self.sign_input_1(context, next_force_skip_connector);
}
}
impl BaseTransaction for ForceSkipKickoffTransaction {
Expand Down Expand Up @@ -399,7 +485,7 @@ impl QuickChallengeTransaction {
input_1,
);

this.pre_sign_and_push(context, guardian_connector, next_force_skip_connector);
this.pre_sign_and_push(context, guardian_connector);

this
}
Expand Down Expand Up @@ -460,29 +546,106 @@ impl QuickChallengeTransaction {
);
}

pub fn sign_input_1(
fn sign_input_1_musig2(
&mut self,
context: &CommitteeContext,
sec_nonce: &SecNonce,
agg_nonce: &AggNonce,
) -> Result<PartialSignature, SigningError> {
let input_index = 1;
let sighash_type = TapSighashType::None;
generate_taproot_partial_signature(
context,
self.tx(),
sec_nonce,
agg_nonce,
input_index,
self.prev_outs(),
&self.prev_scripts()[input_index],
sighash_type,
)
}

fn push_input_1_signature(
&mut self,
context: &OperatorContext,
next_force_skip_connector: &ForceSkipConnector,
input_1_sig: bitcoin::taproot::Signature,
) {
let input_index = 1;
pre_sign_taproot_input_default(
self,
let script = self.prev_scripts()[input_index].clone();
let spend_info = next_force_skip_connector.generate_taproot_spend_info();
let tx_mut = self.tx_mut();
tx_mut.input[input_index]
.witness
.push(input_1_sig.serialize());
push_taproot_leaf_script_and_control_block_to_witness(
tx_mut,
input_index,
TapSighashType::None,
next_force_skip_connector.generate_taproot_spend_info(),
&vec![&context.operator_keypair],
&spend_info,
&script,
);
}

pub fn pre_sign(
&mut self,
context: &CommitteeContext,
sec_nonces: &[SecNonce; 1],
agg_nonces: &[AggNonce; 1],
) -> Result<[PartialSignature; 1], SigningError> {
let input_1_sig = self.sign_input_1_musig2(context, &sec_nonces[0], &agg_nonces[0]);
match [input_1_sig]
.into_iter()
.collect::<Result<Vec<PartialSignature>, SigningError>>()
{
Ok(sigs) => Ok(sigs.try_into().unwrap()),
Err(e) => Err(e),
}
}

pub fn aggregate_pre_sigs(
&self,
context: &dyn BaseContext,
partial_signatures: &[Vec<PartialSignature>; 1],
agg_nonces: &[AggNonce; 1],
) -> Result<[bitcoin::taproot::Signature; 1], Error> {
let input_index = 1;
let sig_index = 0;
let sighash_type = TapSighashType::None;
let input_1_sig = match generate_taproot_aggregated_signature(
context,
self.tx(),
&agg_nonces[sig_index],
input_index,
self.prev_outs(),
&self.prev_scripts()[input_index],
sighash_type,
partial_signatures[sig_index].clone(),
) {
Ok(sig) => bitcoin::taproot::Signature {
signature: sig.into(),
sighash_type,
},
Err(_) => return Err(Error::Other("Failed to aggregate signatures")),
};
Ok([input_1_sig])
}

pub fn push_pre_sigs(
&mut self,
next_force_skip_connector: &ForceSkipConnector,
pre_sigs: [bitcoin::taproot::Signature; 1],
) {
self.push_input_1_signature(next_force_skip_connector, pre_sigs[0]);
}

/// Signs input 0. Input 1 spends the force-skip connector and is signed
/// by the committee through `pre_sign`.
pub fn pre_sign_and_push(
&mut self,
context: &OperatorContext,
guardian_connector: &GuardianConnector,
next_force_skip_connector: &ForceSkipConnector,
) {
self.sign_input_0(context, guardian_connector);
self.sign_input_1(context, next_force_skip_connector);
}
}
impl BaseTransaction for QuickChallengeTransaction {
Expand Down
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