From 861a8352e50d1f2ea0669c3442267aecbc9b1ea8 Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Thu, 19 Sep 2024 21:19:34 -0400
Subject: [PATCH] Update to the latest bitcoin-serai

---
 Cargo.lock                                    |  2 --
 processor/bitcoin/Cargo.toml                  |  2 --
 processor/bitcoin/src/key_gen.rs              | 35 -------------------
 .../bitcoin/src/primitives/transaction.rs     |  3 +-
 4 files changed, 1 insertion(+), 41 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 065432d0..12da8dd6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8106,9 +8106,7 @@ dependencies = [
  "borsh",
  "ciphersuite",
  "dkg",
- "flexible-transcript",
  "hex",
- "k256",
  "log",
  "modular-frost",
  "parity-scale-codec",
diff --git a/processor/bitcoin/Cargo.toml b/processor/bitcoin/Cargo.toml
index 2a69d234..90b9566b 100644
--- a/processor/bitcoin/Cargo.toml
+++ b/processor/bitcoin/Cargo.toml
@@ -23,8 +23,6 @@ hex = { version = "0.4", default-features = false, features = ["std"] }
 scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["std"] }
 borsh = { version = "1", default-features = false, features = ["std", "derive", "de_strict_order"] }
 
-transcript = { package = "flexible-transcript", path = "../../crypto/transcript", default-features = false, features = ["std", "recommended"] }
-k256 = { version = "0.13", default-features = false, features = ["std"] }
 ciphersuite = { path = "../../crypto/ciphersuite", default-features = false, features = ["std", "secp256k1"] }
 dkg = { path = "../../crypto/dkg", default-features = false, features = ["std", "evrf-secp256k1"] }
 frost = { package = "modular-frost", path = "../../crypto/frost", default-features = false }
diff --git a/processor/bitcoin/src/key_gen.rs b/processor/bitcoin/src/key_gen.rs
index bc911676..41544134 100644
--- a/processor/bitcoin/src/key_gen.rs
+++ b/processor/bitcoin/src/key_gen.rs
@@ -1,8 +1,6 @@
 use ciphersuite::{group::GroupEncoding, Ciphersuite, Secp256k1};
 use frost::ThresholdKeys;
 
-use bitcoin_serai::bitcoin::{hashes::Hash, TapTweakHash};
-
 use crate::{primitives::x_coord_to_even_point, scan::scanner};
 
 pub(crate) struct KeyGenParams;
@@ -12,39 +10,6 @@ impl key_gen::KeyGenParams for KeyGenParams {
   type ExternalNetworkCiphersuite = Secp256k1;
 
   fn tweak_keys(keys: &mut ThresholdKeys<Self::ExternalNetworkCiphersuite>) {
-    /*
-      Offset the keys by their hash to prevent a malicious participant from inserting a script
-      path, as specified in
-      https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-23
-
-      This isn't exactly the same, as we then increment the key until it happens to be even, yet
-      the goal is simply that someone who biases the key-gen can't insert their own script path.
-      By adding the hash of the key to the key, anyone who attempts such bias will change the key
-      used (changing the bias necessary).
-
-      This is also potentially unnecessary for Serai, which uses an eVRF-based DKG. While that can
-      be biased (by manipulating who participates as we use it robustly and only require `t`
-      participants), contributions cannot be arbitrarily defined. That presumably requires
-      performing a search of the possible keys for some collision with 2**128 work. It's better to
-      offset regardless and avoid this question however.
-    */
-    {
-      use k256::elliptic_curve::{
-        bigint::{Encoding, U256},
-        ops::Reduce,
-      };
-      let tweak_hash = TapTweakHash::hash(&keys.group_key().to_bytes().as_slice()[1 ..]);
-      /*
-        https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#cite_ref-13-0 states how the
-        bias is negligible. This reduction shouldn't ever occur, yet if it did, the script path
-        would be unusable due to a check the script path hash is less than the order. That doesn't
-        impact us as we don't want the script path to be usable.
-      */
-      *keys = keys.offset(<Secp256k1 as Ciphersuite>::F::reduce(U256::from_be_bytes(
-        *tweak_hash.to_raw_hash().as_ref(),
-      )));
-    }
-
     *keys = bitcoin_serai::wallet::tweak_keys(keys);
     // Also create a scanner to assert these keys, and all expected paths, are usable
     scanner(keys.group_key());
diff --git a/processor/bitcoin/src/primitives/transaction.rs b/processor/bitcoin/src/primitives/transaction.rs
index 8e7a26f6..9b81d2f0 100644
--- a/processor/bitcoin/src/primitives/transaction.rs
+++ b/processor/bitcoin/src/primitives/transaction.rs
@@ -2,7 +2,6 @@ use std::io;
 
 use rand_core::{RngCore, CryptoRng};
 
-use transcript::{Transcript, RecommendedTranscript};
 use ciphersuite::Secp256k1;
 use frost::{dkg::ThresholdKeys, sign::PreprocessMachine};
 
@@ -81,7 +80,7 @@ impl PreprocessMachine for ClonableTransctionMachine {
       .0
       .signable()
       .expect("signing an invalid SignableTransaction")
-      .multisig(&self.1, RecommendedTranscript::new(b"Serai Processor Bitcoin Transaction"))
+      .multisig(&self.1)
       .expect("incorrect keys used for SignableTransaction")
       .preprocess(rng)
   }