Use the IETF transacript in bitcoin-serai, not RecommendedTranscript

This is more likely to be interoperable in the long term.

Cargo.lock

@@ -1054,7 +1054,6 @@ name = "bitcoin-serai"
 version = "0.3.0"
 dependencies = [
  "bitcoin",
- "flexible-transcript",
  "hex",
  "k256",
  "modular-frost",

networks/bitcoin/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bitcoin-serai"
-version = "0.4.0"
+version = "0.3.0"
 description = "A Bitcoin library for FROST-signing transactions"
 license = "MIT"
 repository = "https://github.com/serai-dex/serai/tree/develop/networks/bitcoin"
@@ -26,8 +26,6 @@ rand_core = { version = "0.6", default-features = false }
 bitcoin = { version = "0.32", default-features = false }
 
 k256 = { version = "^0.13.1", default-features = false, features = ["arithmetic", "bits"] }
-
-transcript = { package = "flexible-transcript", path = "../../crypto/transcript", version = "0.3", default-features = false, features = ["recommended"], optional = true }
 frost = { package = "modular-frost", path = "../../crypto/frost", version = "0.8", default-features = false, features = ["secp256k1"], optional = true }
 
 hex = { version = "0.4", default-features = false, optional = true }
@@ -55,8 +53,6 @@ std = [
   "bitcoin/serde",
 
   "k256/std",
-
-  "transcript/std",
   "frost",
 
   "hex/std",

networks/bitcoin/src/crypto.rs

@@ -40,14 +40,12 @@ mod frost_crypto {
 
   use bitcoin::hashes::{HashEngine, Hash, sha256::Hash as Sha256};
 
-  use transcript::Transcript;
-
   use k256::{elliptic_curve::ops::Reduce, U256, Scalar};
 
   use frost::{
     curve::{Ciphersuite, Secp256k1},
     Participant, ThresholdKeys, ThresholdView, FrostError,
-    algorithm::{Hram as HramTrait, Algorithm, Schnorr as FrostSchnorr},
+    algorithm::{Hram as HramTrait, Algorithm, IetfSchnorr as FrostSchnorr},
   };
 
   use super::*;
@@ -82,16 +80,17 @@ mod frost_crypto {
   ///
   /// This must be used with a ThresholdKeys whose group key is even. If it is odd, this will panic.
   #[derive(Clone)]
-  pub struct Schnorr<T: Sync + Clone + Debug + Transcript>(FrostSchnorr<Secp256k1, T, Hram>);
-  impl<T: Sync + Clone + Debug + Transcript> Schnorr<T> {
+  pub struct Schnorr(FrostSchnorr<Secp256k1, Hram>);
+  impl Schnorr {
     /// Construct a Schnorr algorithm continuing the specified transcript.
-    pub fn new(transcript: T) -> Schnorr<T> {
-      Schnorr(FrostSchnorr::new(transcript))
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Schnorr {
+      Schnorr(FrostSchnorr::ietf())
     }
   }
 
-  impl<T: Sync + Clone + Debug + Transcript> Algorithm<Secp256k1> for Schnorr<T> {
-    type Transcript = T;
+  impl Algorithm<Secp256k1> for Schnorr {
+    type Transcript = <FrostSchnorr<Secp256k1, Hram> as Algorithm<Secp256k1>>::Transcript;
     type Addendum = ();
     type Signature = [u8; 64];
 

networks/bitcoin/src/tests/crypto.rs

@@ -3,7 +3,6 @@ use rand_core::OsRng;
 use secp256k1::{Secp256k1 as BContext, Message, schnorr::Signature};
 
 use k256::Scalar;
-use transcript::{Transcript, RecommendedTranscript};
 use frost::{
   curve::Secp256k1,
   Participant,
@@ -25,8 +24,7 @@ fn test_algorithm() {
     *keys = keys.offset(Scalar::from(offset));
   }
 
-  let algo =
-    Schnorr::<RecommendedTranscript>::new(RecommendedTranscript::new(b"bitcoin-serai sign test"));
+  let algo = Schnorr::new();
   let sig = sign(
     &mut OsRng,
     &algo,

networks/bitcoin/src/wallet/send.rs

@@ -7,9 +7,7 @@ use thiserror::Error;
 
 use rand_core::{RngCore, CryptoRng};
 
-use transcript::{Transcript, RecommendedTranscript};
-
-use k256::{elliptic_curve::sec1::ToEncodedPoint, Scalar};
+use k256::Scalar;
 use frost::{curve::Secp256k1, Participant, ThresholdKeys, FrostError, sign::*};
 
 use bitcoin::{
@@ -268,41 +266,15 @@ impl SignableTransaction {
   /// Create a multisig machine for this transaction.
   ///
   /// Returns None if the wrong keys are used.
-  pub fn multisig(
-    self,
-    keys: &ThresholdKeys<Secp256k1>,
-    mut transcript: RecommendedTranscript,
-  ) -> Option<TransactionMachine> {
-    transcript.domain_separate(b"bitcoin_transaction");
-    transcript.append_message(b"root_key", keys.group_key().to_encoded_point(true).as_bytes());
-
-    // Transcript the inputs and outputs
-    let tx = &self.tx;
-    for input in &tx.input {
-      transcript.append_message(b"input_hash", input.previous_output.txid);
-      transcript.append_message(b"input_output_index", input.previous_output.vout.to_le_bytes());
-    }
-    for payment in &tx.output {
-      transcript.append_message(b"output_script", payment.script_pubkey.as_bytes());
-      transcript.append_message(b"output_amount", payment.value.to_sat().to_le_bytes());
-    }
-
+  pub fn multisig(self, keys: &ThresholdKeys<Secp256k1>) -> Option<TransactionMachine> {
     let mut sigs = vec![];
-    for i in 0 .. tx.input.len() {
-      let mut transcript = transcript.clone();
-      // This unwrap is safe since any transaction with this many inputs violates the maximum
-      // size allowed under standards, which this lib will error on creation of
-      transcript.append_message(b"signing_input", u32::try_from(i).unwrap().to_le_bytes());
-
+    for i in 0 .. self.tx.input.len() {
       let offset = keys.clone().offset(self.offsets[i]);
       if p2tr_script_buf(offset.group_key())? != self.prevouts[i].script_pubkey {
         None?;
       }
 
-      sigs.push(AlgorithmMachine::new(
-        Schnorr::new(transcript),
-        keys.clone().offset(self.offsets[i]),
-      ));
+      sigs.push(AlgorithmMachine::new(Schnorr::new(), keys.clone().offset(self.offsets[i])));
     }
 
     Some(TransactionMachine { tx: self, sigs })
@@ -315,7 +287,7 @@ impl SignableTransaction {
 /// This will panic if either `cache` is called or the message isn't empty.
 pub struct TransactionMachine {
   tx: SignableTransaction,
-  sigs: Vec<AlgorithmMachine<Secp256k1, Schnorr<RecommendedTranscript>>>,
+  sigs: Vec<AlgorithmMachine<Secp256k1, Schnorr>>,
 }
 
 impl PreprocessMachine for TransactionMachine {
@@ -344,7 +316,7 @@ impl PreprocessMachine for TransactionMachine {
 
 pub struct TransactionSignMachine {
   tx: SignableTransaction,
-  sigs: Vec<AlgorithmSignMachine<Secp256k1, Schnorr<RecommendedTranscript>>>,
+  sigs: Vec<AlgorithmSignMachine<Secp256k1, Schnorr>>,
 }
 
 impl SignMachine<Transaction> for TransactionSignMachine {
@@ -424,7 +396,7 @@ impl SignMachine<Transaction> for TransactionSignMachine {
 
 pub struct TransactionSignatureMachine {
   tx: Transaction,
-  sigs: Vec<AlgorithmSignatureMachine<Secp256k1, Schnorr<RecommendedTranscript>>>,
+  sigs: Vec<AlgorithmSignatureMachine<Secp256k1, Schnorr>>,
 }
 
 impl SignatureMachine<Transaction> for TransactionSignatureMachine {

networks/bitcoin/tests/wallet.rs

@@ -2,8 +2,6 @@ use std::collections::HashMap;
 
 use rand_core::{RngCore, OsRng};
 
-use transcript::{Transcript, RecommendedTranscript};
-
 use k256::{
   elliptic_curve::{
     group::{ff::Field, Group},
@@ -94,12 +92,7 @@ fn sign(
 ) -> Transaction {
   let mut machines = HashMap::new();
   for i in (1 ..= THRESHOLD).map(|i| Participant::new(i).unwrap()) {
-    machines.insert(
-      i,
-      tx.clone()
-        .multisig(&keys[&i].clone(), RecommendedTranscript::new(b"bitcoin-serai Test Transaction"))
-        .unwrap(),
-    );
+    machines.insert(i, tx.clone().multisig(&keys[&i].clone()).unwrap());
   }
   sign_without_caching(&mut OsRng, machines, &[])
 }

processor/src/networks/bitcoin.rs

@@ -4,7 +4,6 @@ use async_trait::async_trait;
 
 use scale::{Encode, Decode};
 
-use transcript::{Transcript, RecommendedTranscript};
 use ciphersuite::group::ff::PrimeField;
 use k256::{ProjectivePoint, Scalar};
 use frost::{
@@ -249,7 +248,6 @@ impl EventualityTrait for Eventuality {
 
 #[derive(Clone, Debug)]
 pub struct SignableTransaction {
-  transcript: RecommendedTranscript,
   actual: BSignableTransaction,
 }
 impl PartialEq for SignableTransaction {
@@ -820,7 +818,7 @@ impl Network for Bitcoin {
   async fn signable_transaction(
     &self,
     block_number: usize,
-    plan_id: &[u8; 32],
+    _plan_id: &[u8; 32],
     _key: ProjectivePoint,
     inputs: &[Output],
     payments: &[Payment<Self>],
@@ -829,12 +827,8 @@ impl Network for Bitcoin {
   ) -> Result<Option<(Self::SignableTransaction, Self::Eventuality)>, NetworkError> {
     Ok(self.make_signable_transaction(block_number, inputs, payments, change, false).await?.map(
       |signable| {
-        let mut transcript =
-          RecommendedTranscript::new(b"Serai Processor Bitcoin Transaction Transcript");
-        transcript.append_message(b"plan", plan_id);
-
         let eventuality = Eventuality(signable.txid());
-        (SignableTransaction { transcript, actual: signable }, eventuality)
+        (SignableTransaction { actual: signable }, eventuality)
       },
     ))
   }
@@ -844,13 +838,7 @@ impl Network for Bitcoin {
     keys: ThresholdKeys<Self::Curve>,
     transaction: Self::SignableTransaction,
   ) -> Result<Self::TransactionMachine, NetworkError> {
-    Ok(
-      transaction
-        .actual
-        .clone()
-        .multisig(&keys, transaction.transcript)
-        .expect("used the wrong keys"),
-    )
+    Ok(transaction.actual.clone().multisig(&keys).expect("used the wrong keys"))
   }
 
   async fn publish_completion(&self, tx: &Transaction) -> Result<(), NetworkError> {