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make verify_kzg_proof apis more closely mimic the specs (#46)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| package kzg | ||
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| import ( | ||
| "errors" | ||
| "fmt" | ||
|
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| "github.com/protolambda/go-kzg/bls" | ||
|
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| "github.com/ethereum/go-ethereum/crypto" | ||
| "github.com/ethereum/go-ethereum/params" | ||
| ) | ||
|
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| // VerifyKZGProof implements verify_kzg_proof from the EIP-4844 consensus spec: | ||
| // https://github.com/ethereum/consensus-specs/blob/dev/specs/eip4844/polynomial-commitments.md#verify_kzg_proof | ||
| func VerifyKZGProof(polynomialKZG [48]byte, z *bls.Fr, y *bls.Fr, kzgProof [48]byte) (bool, error) { | ||
| polynomialKZGG1, err := bls.FromCompressedG1(polynomialKZG[:]) | ||
| if err != nil { | ||
| return false, fmt.Errorf("failed to decode polynomialKZG: %v", err) | ||
| } | ||
| kzgProofG1, err := bls.FromCompressedG1(kzgProof[:]) | ||
| if err != nil { | ||
| return false, fmt.Errorf("failed to decode kzgProof: %v", err) | ||
| } | ||
| return VerifyKZGProofFromPoints(polynomialKZGG1, z, y, kzgProofG1), nil | ||
| } | ||
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| func VerifyKZGProofFromPoints(polynomialKZG *bls.G1Point, z *bls.Fr, y *bls.Fr, kzgProof *bls.G1Point) bool { | ||
| var zG2 bls.G2Point | ||
| bls.MulG2(&zG2, &bls.GenG2, z) | ||
| var yG1 bls.G1Point | ||
| bls.MulG1(&yG1, &bls.GenG1, y) | ||
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| var xMinusZ bls.G2Point | ||
| bls.SubG2(&xMinusZ, &kzgSetupG2[1], &zG2) | ||
| var pMinusY bls.G1Point | ||
| bls.SubG1(&pMinusY, polynomialKZG, &yG1) | ||
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| return bls.PairingsVerify(&pMinusY, &bls.GenG2, kzgProof, &xMinusZ) | ||
| } | ||
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| // KZGToVersionedHash implements kzg_to_versioned_hash from EIP-4844 | ||
| func KZGToVersionedHash(kzg [48]byte) [32]byte { | ||
| h := crypto.Keccak256Hash(kzg[:]) | ||
| h[0] = params.BlobCommitmentVersionKZG | ||
| return h | ||
| } | ||
|
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| // PointEvaluationPrecompile implements point_evaluation_precompile from EIP-4844 | ||
| func PointEvaluationPrecompile(input []byte) ([]byte, error) { | ||
| if len(input) != 192 { | ||
| return nil, errors.New("invalid input length") | ||
| } | ||
|
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| // versioned hash: first 32 bytes | ||
| var versionedHash [32]byte | ||
| copy(versionedHash[:], input[:32]) | ||
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| var x, y [32]byte | ||
| // Evaluation point: next 32 bytes | ||
| copy(x[:], input[32:64]) | ||
| // Expected output: next 32 bytes | ||
| copy(y[:], input[64:96]) | ||
|
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| // successfully converting x and y to bls.Fr confirms they are < MODULUS per the spec | ||
| var xFr, yFr bls.Fr | ||
| ok := bls.FrFrom32(&xFr, x) | ||
| if !ok { | ||
| return nil, errors.New("invalid evaluation point") | ||
| } | ||
| ok = bls.FrFrom32(&yFr, y) | ||
| if !ok { | ||
| return nil, errors.New("invalid expected output") | ||
| } | ||
|
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| // input kzg point: next 48 bytes | ||
| var dataKZG [48]byte | ||
| copy(dataKZG[:], input[96:144]) | ||
| if KZGToVersionedHash(dataKZG) != versionedHash { | ||
| return nil, errors.New("mismatched versioned hash") | ||
| } | ||
|
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| // Quotient kzg: next 48 bytes | ||
| var quotientKZG [48]byte | ||
| copy(quotientKZG[:], input[144:192]) | ||
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| ok, err := VerifyKZGProof(dataKZG, &xFr, &yFr, quotientKZG) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("verify_kzg_proof error: %v", err) | ||
| } | ||
| if !ok { | ||
| return nil, errors.New("failed to verify kzg proof") | ||
| } | ||
| return []byte{}, nil | ||
| } |
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