feat(backend/solidity): Implement BLS12-381 pairing precompile (0x0a). #1368

backend/solidity/bls12_381_pairing.go

@@ -0,0 +1,65 @@
+package solidity
+
+import (
+	"errors"
+	"math/big"
+
+	"github.com/consensys/gnark-crypto/ecc/bls12-381"
+	"github.com/consensys/gnark-crypto/ecc/bls12-381/fp"
+	"github.com/consensys/gnark-crypto/ecc/bls12-381/fr"
+)
+
+// BLS12381PairingPrecompile implements the BLS12-381 pairing check precompile (0x0a)
+// as specified in EIP-2537.
+type BLS12381PairingPrecompile struct{}
+
+// Input length for a single pairing check: 2 * 3 * 64 = 384 bytes
+const pairLength = 384
+
+// Run implements the BLS12-381 pairing check precompile
+func (b *BLS12381PairingPrecompile) Run(input []byte) ([]byte, error) {
+	// Input length must be a multiple of 384 bytes (pairs of G1, G2 points)
+	if len(input)%pairLength != 0 {
+		return nil, errors.New("invalid input length")
+	}
+
+	// If input is empty, return 1 (vacuously true)
+	if len(input) == 0 {
+		return []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, nil
+	}
+
+	// Process each pair
+	var product bls12381.GT
+	product.SetOne()
+
+	for i := 0; i < len(input); i += pairLength {
+		pair := input[i : i+pairLength]
+
+		// Parse G1 point (first 128 bytes)
+		var g1 bls12381.G1Affine
+		if _, err := g1.SetBytes(pair[:128]); err != nil {
+			return nil, errors.New("invalid G1 point")
+		}
+
+		// Parse G2 point (next 256 bytes)
+		var g2 bls12381.G2Affine
+		if _, err := g2.SetBytes(pair[128:]); err != nil {
+			return nil, errors.New("invalid G2 point")
+		}
+
+		// Check if points are in correct subgroup
+		if !g1.IsInSubGroup() || !g2.IsInSubGroup() {
+			return nil, errors.New("point not in correct subgroup")
+		}
+
+		// Calculate pairing and multiply with product
+		res, _ := bls12381.Pair([]bls12381.G1Affine{g1}, []bls12381.G2Affine{g2})
+		product.Mul(&product, &res)
+	}
+
+	// Check if final product equals 1
+	if product.IsOne() {
+		return []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, nil
+	}
+	return []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, nil
+} 

backend/solidity/bls12_381_pairing_test.go

@@ -0,0 +1,44 @@
+package solidity
+
+import (
+	"testing"
+
+	"github.com/consensys/gnark-crypto/ecc/bls12-381"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBLS12381PairingPrecompile(t *testing.T) {
+	precompile := &BLS12381PairingPrecompile{}
+
+	t.Run("empty input", func(t *testing.T) {
+		result, err := precompile.Run([]byte{})
+		require.NoError(t, err)
+		require.Equal(t, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, result)
+	})
+
+	t.Run("invalid input length", func(t *testing.T) {
+		_, err := precompile.Run(make([]byte, 100))
+		require.Error(t, err)
+	})
+
+	t.Run("valid pairing check", func(t *testing.T) {
+		// Generate valid test points
+		var g1 bls12381.G1Affine
+		var g2 bls12381.G2Affine
+		g1.Generator()
+		g2.Generator()
+
+		// Serialize points
+		g1Bytes := g1.Bytes()
+		g2Bytes := g2.Bytes()
+
+		// Combine into input
+		input := make([]byte, pairLength)
+		copy(input[:128], g1Bytes[:])
+		copy(input[128:], g2Bytes[:])
+
+		result, err := precompile.Run(input)
+		require.NoError(t, err)
+		require.Equal(t, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, result)
+	})
+}