Add test helpers to produce commitments and proofs (#13242)

* Add test helpers to produce commitments and proofs

* go mod tidy

---------

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

beacon-chain/blockchain/kzg/BUILD.bazel

@@ -26,6 +26,8 @@ go_test(
     deps = [
         "//proto/prysm/v1alpha1:go_default_library",
         "//testing/require:go_default_library",
+        "@com_github_consensys_gnark_crypto//ecc/bls12-381/fr:go_default_library",
         "@com_github_crate_crypto_go_kzg_4844//:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
     ],
 )

beacon-chain/blockchain/kzg/validation_test.go

@@ -1,13 +1,63 @@
 package kzg
 
 import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/binary"
 	"testing"
 
+	"github.com/consensys/gnark-crypto/ecc/bls12-381/fr"
 	GoKZG "github.com/crate-crypto/go-kzg-4844"
 	ethpb "github.com/prysmaticlabs/prysm/v4/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/v4/testing/require"
+	"github.com/sirupsen/logrus"
 )
 
+func deterministicRandomness(seed int64) [32]byte {
+	// Converts an int64 to a byte slice
+	buf := new(bytes.Buffer)
+	err := binary.Write(buf, binary.BigEndian, seed)
+	if err != nil {
+		logrus.WithError(err).Error("Failed to write int64 to bytes buffer")
+		return [32]byte{}
+	}
+	bytes := buf.Bytes()
+
+	return sha256.Sum256(bytes)
+}
+
+// Returns a serialized random field element in big-endian
+func GetRandFieldElement(seed int64) [32]byte {
+	bytes := deterministicRandomness(seed)
+	var r fr.Element
+	r.SetBytes(bytes[:])
+
+	return GoKZG.SerializeScalar(r)
+}
+
+// Returns a random blob using the passed seed as entropy
+func GetRandBlob(seed int64) GoKZG.Blob {
+	var blob GoKZG.Blob
+	bytesPerBlob := GoKZG.ScalarsPerBlob * GoKZG.SerializedScalarSize
+	for i := 0; i < bytesPerBlob; i += GoKZG.SerializedScalarSize {
+		fieldElementBytes := GetRandFieldElement(seed + int64(i))
+		copy(blob[i:i+GoKZG.SerializedScalarSize], fieldElementBytes[:])
+	}
+	return blob
+}
+
+func GenerateCommitmentAndProof(blob GoKZG.Blob) (GoKZG.KZGCommitment, GoKZG.KZGProof, error) {
+	commitment, err := kzgContext.BlobToKZGCommitment(blob, 0)
+	if err != nil {
+		return GoKZG.KZGCommitment{}, GoKZG.KZGProof{}, err
+	}
+	proof, err := kzgContext.ComputeBlobKZGProof(blob, commitment, 0)
+	if err != nil {
+		return GoKZG.KZGCommitment{}, GoKZG.KZGProof{}, err
+	}
+	return commitment, proof, err
+}
+
 func TestIsDataAvailable(t *testing.T) {
 	sidecars := make([]*ethpb.DeprecatedBlobSidecar, 0)
 	commitments := make([][]byte, 0)
@@ -23,3 +73,13 @@ func TestBytesToAny(t *testing.T) {
 	require.DeepEqual(t, commitment, bytesToCommitment(bytes))
 	require.DeepEqual(t, proof, bytesToKZGProof(bytes))
 }
+
+func TestGenerateCommitmentAndProof(t *testing.T) {
+	blob := GetRandBlob(123)
+	commitment, proof, err := GenerateCommitmentAndProof(blob)
+	require.NoError(t, err)
+	expectedCommitment := GoKZG.KZGCommitment{180, 218, 156, 194, 59, 20, 10, 189, 186, 254, 132, 93, 7, 127, 104, 172, 238, 240, 237, 70, 83, 89, 1, 152, 99, 0, 165, 65, 143, 62, 20, 215, 230, 14, 205, 95, 28, 245, 54, 25, 160, 16, 178, 31, 232, 207, 38, 85}
+	expectedProof := GoKZG.KZGProof{128, 110, 116, 170, 56, 111, 126, 87, 229, 234, 211, 42, 110, 150, 129, 206, 73, 142, 167, 243, 90, 149, 240, 240, 236, 204, 143, 182, 229, 249, 81, 27, 153, 171, 83, 70, 144, 250, 42, 1, 188, 215, 71, 235, 30, 7, 175, 86}
+	require.Equal(t, expectedCommitment, commitment)
+	require.Equal(t, expectedProof, proof)
+}

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/aristanetworks/goarista v0.0.0-20200805130819-fd197cf57d96
 	github.com/bazelbuild/rules_go v0.23.2
 	github.com/btcsuite/btcd/btcec/v2 v2.3.2
+	github.com/consensys/gnark-crypto v0.12.1
 	github.com/crate-crypto/go-kzg-4844 v0.7.0
 	github.com/d4l3k/messagediff v1.2.1
 	github.com/dgraph-io/ristretto v0.0.4-0.20210318174700-74754f61e018
@@ -114,7 +115,6 @@ require (
 	github.com/cockroachdb/redact v1.1.3 // indirect
 	github.com/cockroachdb/tokenbucket v0.0.0-20230807174530-cc333fc44b06 // indirect
 	github.com/consensys/bavard v0.1.13 // indirect
-	github.com/consensys/gnark-crypto v0.12.1 // indirect
 	github.com/containerd/cgroups v1.1.0 // indirect
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect