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perf(bls): remove redundant G2 subgroup check in signature verification #782

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perf(bls): remove redundant G2 subgroup check in signature verification #782

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37 changes: 1 addition & 36 deletions ethereum/consensus-core/src/types/bls.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
use bls12_381::{
hash_to_curve::{ExpandMsgXmd, HashToCurve},
multi_miller_loop, G1Affine, G1Projective, G2Affine, G2Prepared, G2Projective, Gt, Scalar,
multi_miller_loop, G1Affine, G1Projective, G2Affine, G2Prepared, G2Projective, Gt,
};
use eyre::{eyre, Result};
use serde::{Deserialize, Serialize};
Expand Down Expand Up @@ -44,11 +44,6 @@ impl Signature {
return false;
};

// Subgroup check for signature
if !subgroup_check_g2(&sig_point) {
return false;
}

verify_with_aggregate_pk(&sig_point, msg, aggregate_public_key)
}

Expand Down Expand Up @@ -84,14 +79,6 @@ fn verify_with_aggregate_pk(
ate2_evaluation(sig_point, &generator_g1_negative, &msg_hash, &key_point)
}

/// Verifies a G2 point is in subgroup `r`.
fn subgroup_check_g2(point: &G2Affine) -> bool {
const CURVE_ORDER: &str = "73EDA753299D7D483339D80809A1D80553BDA402FFFE5BFEFFFFFFFF00000001";
let r = hex_to_scalar(CURVE_ORDER).unwrap();
let check = point * r;
check.is_identity().into()
}

/// Evaluation of e(S, -G1) * e(H, PK) == 1
fn ate2_evaluation(p1: &G2Affine, q1: &G1Affine, r1: &G2Affine, s1: &G1Affine) -> bool {
// Prepare G2 points for efficient pairing
Expand All @@ -113,25 +100,3 @@ fn hash_to_curve(msg: &[u8]) -> G2Projective {
const DST: &[u8] = b"BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_";
<G2Projective as HashToCurve<ExpandMsgXmd<sha2::Sha256>>>::hash_to_curve(msg, DST)
}

/// Converts hex string to scalar
fn hex_to_scalar(hex: &str) -> Option<Scalar> {
if hex.len() != 64 {
return None;
}

let mut raw = [0u64; 4];
for (i, chunk) in hex.as_bytes().chunks(16).enumerate().take(4) {
if let Ok(hex_chunk) = core::str::from_utf8(chunk) {
if let Ok(value) = u64::from_str_radix(hex_chunk, 16) {
raw[3 - i] = value.to_le();
} else {
return None;
}
} else {
return None;
}
}

Some(Scalar::from_raw(raw))
}