fix: use the little-endian representation for serialized values in KZG Pointeval precompile (#1614)

Author: ivokub

std/evmprecompiles/10-kzg_point_evaluation.go

@@ -123,7 +123,7 @@ func KzgPointEvaluation(
 	// versioned hash
 	var versionedHashBytes [sha256.Size]uints.U8
 	for i := range versionedHash {
-		res, err := conversion.NativeToBytes(api, versionedHash[len(versionedHash)-1-i])
+		res, err := conversion.NativeToBytes(api, versionedHash[i])
 		if err != nil {
 			return fmt.Errorf("convert versioned hash element %d to bytes: %w", i, err)
 		}
@@ -133,7 +133,7 @@ func KzgPointEvaluation(
 	// commitment
 	var comSerializedBytes [bls12381.SizeOfG1AffineCompressed]uints.U8
 	for i := range commitmentCompressed {
-		res, err := conversion.NativeToBytes(api, commitmentCompressed[len(commitmentCompressed)-1-i])
+		res, err := conversion.NativeToBytes(api, commitmentCompressed[i])
 		if err != nil {
 			return fmt.Errorf("convert commitment element %d to bytes: %w", i, err)
 		}
@@ -142,7 +142,7 @@ func KzgPointEvaluation(
 	// proof
 	var proofSerialisedBytes [bls12381.SizeOfG1AffineCompressed]uints.U8
 	for i := range proofCompressed {
-		res, err := conversion.NativeToBytes(api, proofCompressed[len(proofCompressed)-1-i])
+		res, err := conversion.NativeToBytes(api, proofCompressed[i])
 		if err != nil {
 			return fmt.Errorf("convert proof element %d to bytes: %w", i, err)
 		}
@@ -289,8 +289,8 @@ func KzgPointEvaluationFailure(
 		Y: *fp.NewElement(0),
 	}
 	dummyVersionedHash := []frontend.Variable{
-		"0xdef7ab966d7b770905398eba3c444014",
 		"0x010657f37554c781402a22917dee2f75",
+		"0xdef7ab966d7b770905398eba3c444014",
 	}
 	// -- check that the masks of compressed commitment and proof are correct
 	// (infinity, small y, large y). If either of them is not correct, then we
@@ -300,15 +300,15 @@ func KzgPointEvaluationFailure(
 	// - first we unpack the packed commitment and proof into bytes
 	var comSerializedBytes [bls12381.SizeOfG1AffineCompressed]uints.U8
 	for i := range commitmentCompressed {
-		res, err := conversion.NativeToBytes(api, commitmentCompressed[len(commitmentCompressed)-1-i])
+		res, err := conversion.NativeToBytes(api, commitmentCompressed[i])
 		if err != nil {
 			return fmt.Errorf("convert commitment element %d to bytes: %w", i, err)
 		}
 		copy(comSerializedBytes[i*16:(i+1)*16], res[16:])
 	}
 	var proofSerialisedBytes [bls12381.SizeOfG1AffineCompressed]uints.U8
 	for i := range proofCompressed {
-		res, err := conversion.NativeToBytes(api, proofCompressed[len(proofCompressed)-1-i])
+		res, err := conversion.NativeToBytes(api, proofCompressed[i])
 		if err != nil {
 			return fmt.Errorf("convert proof element %d to bytes: %w", i, err)
 		}
@@ -458,7 +458,7 @@ func KzgPointEvaluationFailure(
 	// - first map the versioned hash to bytes
 	var versionedHashBytes [sha256.Size]uints.U8
 	for i := range versionedHash {
-		res, err := conversion.NativeToBytes(api, versionedHash[len(versionedHash)-1-i])
+		res, err := conversion.NativeToBytes(api, versionedHash[i])
 		if err != nil {
 			return fmt.Errorf("convert versioned hash element %d to bytes: %w", i, err)
 		}

std/evmprecompiles/10-kzg_point_evaluation_test.go

@@ -80,21 +80,21 @@ func TestKzgPointEvaluationPrecompile(t *testing.T) {
 	h[0] = blobCommitmentVersionKZG
 
 	witnessHash := [2]frontend.Variable{
-		encode(h[16:32]),
 		encode(h[0:16]),
+		encode(h[16:32]),
 	}
 	// - commitment into 3 limbs
 	witnessCommitment := [3]frontend.Variable{
-		encode(commitmentBytes[32:48]),
-		encode(commitmentBytes[16:32]),
 		encode(commitmentBytes[0:16]),
+		encode(commitmentBytes[16:32]),
+		encode(commitmentBytes[32:48]),
 	}
 	// - proof into 3 limbs
 	proofUncompressed := kzgProof.H.Bytes()
 	witnessProof := [3]frontend.Variable{
-		encode(proofUncompressed[32:48]),
-		encode(proofUncompressed[16:32]),
 		encode(proofUncompressed[0:16]),
+		encode(proofUncompressed[16:32]),
+		encode(proofUncompressed[32:48]),
 	}
 
 	// prepare the constant return values
@@ -141,20 +141,20 @@ func (c *kzgPointEvalFailureCircuit) Define(api frontend.API) error {
 
 func runFailureCircuit(_ *test.Assert, evaluationPoint fr.Element, claimedValue fr.Element, hashBytes []byte, commitmentBytes [48]byte, proofBytes [48]byte, blobSize []int, blsModulus []string) error {
 	witnessHash := [2]frontend.Variable{
-		encode(hashBytes[16:32]),
 		encode(hashBytes[0:16]),
+		encode(hashBytes[16:32]),
 	}
 	// - commitment into 3 limbs
 	witnessCommitment := [3]frontend.Variable{
-		encode(commitmentBytes[32:48]),
-		encode(commitmentBytes[16:32]),
 		encode(commitmentBytes[0:16]),
+		encode(commitmentBytes[16:32]),
+		encode(commitmentBytes[32:48]),
 	}
 	// - proof into 3 limbs
 	witnessProof := [3]frontend.Variable{
-		encode(proofBytes[32:48]),
-		encode(proofBytes[16:32]),
 		encode(proofBytes[0:16]),
+		encode(proofBytes[16:32]),
+		encode(proofBytes[32:48]),
 	}
 
 	// prepare the constant return values