--- /dev/null
+//! Defines a Taproot-specific signer type.
+
+use bitcoin::blockdata::transaction::Transaction;
+use bitcoin::secp256k1;
+use bitcoin::secp256k1::{PublicKey, schnorr::Signature, Secp256k1, SecretKey};
+
+use musig2::types::{PartialSignature, PublicNonce};
+
+use crate::ln::chan_utils::{ClosingTransaction, CommitmentTransaction, HolderCommitmentTransaction, HTLCOutputInCommitment};
+use crate::ln::msgs::PartialSignatureWithNonce;
+use crate::ln::PaymentPreimage;
+use crate::sign::{ChannelSigner, HTLCDescriptor};
+
+/// A Taproot-specific signer type that defines signing-related methods that are either unique to
+/// Taproot or have argument or return types that differ from the ones an ECDSA signer would be
+/// expected to have.
+pub trait TaprootChannelSigner: ChannelSigner {
+ /// Generate a local nonce pair, which requires committing to ahead of time.
+ /// The counterparty needs the public nonce generated herein to compute a partial signature.
+ fn generate_local_nonce_pair(&self, commitment_number: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicNonce;
+
+ /// Create a signature for a counterparty's commitment transaction and associated HTLC transactions.
+ ///
+ /// Note that if signing fails or is rejected, the channel will be force-closed.
+ ///
+ /// Policy checks should be implemented in this function, including checking the amount
+ /// sent to us and checking the HTLCs.
+ ///
+ /// The preimages of outgoing HTLCs that were fulfilled since the last commitment are provided.
+ /// A validating signer should ensure that an HTLC output is removed only when the matching
+ /// preimage is provided, or when the value to holder is restored.
+ ///
+ /// Note that all the relevant preimages will be provided, but there may also be additional
+ /// irrelevant or duplicate preimages.
+ //
+ // TODO: Document the things someone using this interface should enforce before signing.
+ fn partially_sign_counterparty_commitment(&self, counterparty_nonce: PublicNonce,
+ commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>,
+ secp_ctx: &Secp256k1<secp256k1::All>,
+ ) -> Result<(PartialSignatureWithNonce, Vec<Signature>), ()>;
+
+ /// Creates a signature for a holder's commitment transaction.
+ ///
+ /// This will be called
+ /// - with a non-revoked `commitment_tx`.
+ /// - with the latest `commitment_tx` when we initiate a force-close.
+ ///
+ /// This may be called multiple times for the same transaction.
+ ///
+ /// An external signer implementation should check that the commitment has not been revoked.
+ ///
+ // TODO: Document the things someone using this interface should enforce before signing.
+ fn finalize_holder_commitment(&self, commitment_number: u64,
+ commitment_tx: &HolderCommitmentTransaction,
+ counterparty_partial_signature: PartialSignatureWithNonce,
+ secp_ctx: &Secp256k1<secp256k1::All>
+ ) -> Result<PartialSignature, ()>;
+
+ /// Create a signature for the given input in a transaction spending an HTLC transaction output
+ /// or a commitment transaction `to_local` output when our counterparty broadcasts an old state.
+ ///
+ /// A justice transaction may claim multiple outputs at the same time if timelocks are
+ /// similar, but only a signature for the input at index `input` should be signed for here.
+ /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
+ /// to an upcoming timelock expiration.
+ ///
+ /// Amount is value of the output spent by this input, committed to in the BIP 341 signature.
+ ///
+ /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
+ /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
+ /// not allow the spending of any funds by itself (you need our holder `revocation_secret` to do
+ /// so).
+ fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64,
+ per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>,
+ ) -> Result<Signature, ()>;
+
+ /// Create a signature for the given input in a transaction spending a commitment transaction
+ /// HTLC output when our counterparty broadcasts an old state.
+ ///
+ /// A justice transaction may claim multiple outputs at the same time if timelocks are
+ /// similar, but only a signature for the input at index `input` should be signed for here.
+ /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
+ /// to an upcoming timelock expiration.
+ ///
+ /// `amount` is the value of the output spent by this input, committed to in the BIP 341
+ /// signature.
+ ///
+ /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
+ /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
+ /// not allow the spending of any funds by itself (you need our holder revocation_secret to do
+ /// so).
+ ///
+ /// `htlc` holds HTLC elements (hash, timelock), thus changing the format of the witness script
+ /// (which is committed to in the BIP 341 signatures).
+ fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64,
+ per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment,
+ secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
+
+ /// Computes the signature for a commitment transaction's HTLC output used as an input within
+ /// `htlc_tx`, which spends the commitment transaction at index `input`. The signature returned
+ /// must be be computed using [`TapSighashType::Default`].
+ ///
+ /// Note that this may be called for HTLCs in the penultimate commitment transaction if a
+ /// [`ChannelMonitor`] [replica](https://github.com/lightningdevkit/rust-lightning/blob/main/GLOSSARY.md#monitor-replicas)
+ /// broadcasts it before receiving the update for the latest commitment transaction.
+ ///
+ ///
+ /// [`TapSighashType::Default`]: bitcoin::sighash::TapSighashType::Default
+ /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
+ fn sign_holder_htlc_transaction(&self, htlc_tx: &Transaction, input: usize,
+ htlc_descriptor: &HTLCDescriptor, secp_ctx: &Secp256k1<secp256k1::All>,
+ ) -> Result<Signature, ()>;
+
+ /// Create a signature for a claiming transaction for a HTLC output on a counterparty's commitment
+ /// transaction, either offered or received.
+ ///
+ /// Such a transaction may claim multiples offered outputs at same time if we know the
+ /// preimage for each when we create it, but only the input at index `input` should be
+ /// signed for here. It may be called multiple times for same output(s) if a fee-bump is
+ /// needed with regards to an upcoming timelock expiration.
+ ///
+ /// `witness_script` is either an offered or received script as defined in BOLT3 for HTLC
+ /// outputs.
+ ///
+ /// `amount` is value of the output spent by this input, committed to in the BIP 341 signature.
+ ///
+ /// `per_commitment_point` is the dynamic point corresponding to the channel state
+ /// detected onchain. It has been generated by our counterparty and is used to derive
+ /// channel state keys, which are then included in the witness script and committed to in the
+ /// BIP 341 signature.
+ fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64,
+ per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment,
+ secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
+
+ /// Create a signature for a (proposed) closing transaction.
+ ///
+ /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
+ /// chosen to forgo their output as dust.
+ fn partially_sign_closing_transaction(&self, closing_tx: &ClosingTransaction,
+ secp_ctx: &Secp256k1<secp256k1::All>) -> Result<PartialSignature, ()>;
+
+ /// Computes the signature for a commitment transaction's anchor output used as an
+ /// input within `anchor_tx`, which spends the commitment transaction, at index `input`.
+ fn sign_holder_anchor_input(
+ &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+ ) -> Result<Signature, ()>;
+
+ // TODO: sign channel announcement
+}
projects / rust-lightning / commitdiff