refactor(zk_verifier): reuse HashToField from cometbls/crypto/bn254

Signed-off-by: Himess <95512809+Himess@users.noreply.github.com>

Author: Himess

11-cometbls/zk_verifier.go

@@ -15,6 +15,7 @@ import (
 	backend "github.com/consensys/gnark/backend/groth16"
 	backend_bn254 "github.com/consensys/gnark/backend/groth16/bn254"
 	"github.com/holiman/uint256"
+	comet "github.com/unionlabs/cometbls/crypto/bn254"
 	"golang.org/x/crypto/sha3"
 )
 
@@ -155,26 +156,6 @@ func (zkp ZKP) Verify(trustedValidatorsHash []byte, header ProverLightHeader) er
 	return verifyingKey.CommitmentKey.Verify(zkp.ProofCommitment, zkp.ProofCommitmentPoK)
 }
 
-func hashToField(msg []byte) fr.Element {
-	hmac := hmac.New(Hash, []byte(CometblsHMACKey))
-	hmac.Write(msg)
-	modMinusOne := new(big.Int).Sub(fr.Modulus(), big.NewInt(1))
-	num := new(big.Int).SetBytes(hmac.Sum(nil))
-	num.Mod(num, modMinusOne)
-	num.Add(num, big.NewInt(1))
-	val, overflow := uint256.FromBig(num)
-	if overflow {
-		panic("impossible; qed;")
-	}
-	valBytes := val.Bytes32()
-	var element fr.Element
-	err := element.SetBytesCanonical(valBytes[:])
-	if err != nil {
-		panic("impossible; qed;")
-	}
-	return element
-}
-
 func commitmentsHash(proofCommitment curve.G1Affine) fr.Element {
 	var buffer [64]byte
 
@@ -184,7 +165,7 @@ func commitmentsHash(proofCommitment curve.G1Affine) fr.Element {
 	y := proofCommitment.Y.Bytes()
 	copy(buffer[32:64], y[:])
 
-	return hashToField(buffer[:])
+	return comet.HashToField(buffer[:])
 }
 
 func inputsHash(header ProverLightHeader, trustedValidatorsHash []byte) fr.Element {
@@ -214,4 +195,4 @@ func inputsHash(header ProverLightHeader, trustedValidatorsHash []byte) fr.Eleme
 	var e fr.Element
 	e.SetBytes(hash[1:])
 	return e
-}
+}

11-cometbls/zk_verifier_test.go

@@ -21,7 +21,7 @@ func TestVerifier(t *testing.T) {
 	err = zkp.Verify(
 
 		trustedValHash,
-		LightHeader{
+		ProverLightHeader{
 			ChainId:            "union-devnet-1337",
 			Height:             3405691582,
 			Time:               time.Unix(1710783278, 499600406),