Add utils for compact RSV encoding/decoding

Signed-off-by: Peter Broadhurst <peter.broadhurst@kaleido.io>

internal/signermsgs/en_error_messges.go

@@ -103,4 +103,5 @@ var (
 	MsgInvalidEIP1559Transaction   = ffe("FF22084", "Transaction payload invalid (EIP-1559): %v")
 	MsgInvalidEIP155TransactionV   = ffe("FF22085", "Invalid V value from EIP-155 transaction (chainId=%d)")
 	MsgInvalidChainID              = ffe("FF22086", "Invalid chainId expected=%d actual=%d")
+	MsgSigningInvalidCompactRSV    = ffe("FF22087", "Invalid signature data (compact R,S,V) length=%d (expected=65)")
 )

pkg/secp256k1/keypair.go

@@ -45,8 +45,7 @@ func GenerateSecp256k1KeyPair() (*KeyPair, error) {
 
 // Deprecated: Note there is no error condition returned by this function (use KeyPairFromBytes)
 func NewSecp256k1KeyPair(b []byte) (*KeyPair, error) {
-	key, pubKey := btcec.PrivKeyFromBytes(b)
-	return wrapSecp256k1Key(key, pubKey), nil
+	return KeyPairFromBytes(b), nil
 }
 
 func KeyPairFromBytes(b []byte) *KeyPair {

pkg/secp256k1/keypair_test.go

@@ -17,6 +17,7 @@
 package secp256k1
 
 import (
+	"context"
 	"math/big"
 	"testing"
 
@@ -57,6 +58,16 @@ func TestGeneratedKeyRoundTrip(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, keypair.Address, *addr)
 
+	sigRSV := sig.CompactRSV()
+	sig2, err := DecodeCompactRSV(context.Background(), sigRSV)
+	assert.NoError(t, err)
+	addr, err = sig2.Recover(data, 1001)
+	assert.NoError(t, err)
+	assert.Equal(t, keypair.Address, *addr)
+
+	_, err = DecodeCompactRSV(context.Background(), []byte("wrong"))
+	assert.Regexp(t, "FF22087", err)
+
 	_, err = sig.Recover(data, 42)
 	assert.Regexp(t, "invalid V value in signature", err)
 

pkg/secp256k1/signer.go

@@ -17,10 +17,13 @@
 package secp256k1
 
 import (
+	"context"
 	"fmt"
 	"math/big"
 
 	ecdsa "github.com/btcsuite/btcd/btcec/v2/ecdsa"
+	"github.com/hyperledger/firefly-common/pkg/i18n"
+	"github.com/hyperledger/firefly-signer/internal/signermsgs"
 	"github.com/hyperledger/firefly-signer/pkg/ethtypes"
 	"golang.org/x/crypto/sha3"
 )
@@ -99,6 +102,26 @@ func (s *SignatureData) RecoverDirect(message []byte, chainID int64) (a *ethtype
 	return PublicKeyToAddress(pubKey), nil
 }
 
+// We use the ethereum convention of R,S,V for compact packing (mentioned because Golang tends to prefer V,R,S)
+func (s *SignatureData) CompactRSV() []byte {
+	signatureBytes := make([]byte, 65)
+	s.R.FillBytes(signatureBytes[0:32])
+	s.S.FillBytes(signatureBytes[32:64])
+	signatureBytes[64] = byte(s.V.Int64())
+	return signatureBytes
+}
+
+func DecodeCompactRSV(ctx context.Context, compactRSV []byte) (*SignatureData, error) {
+	if len(compactRSV) != 65 {
+		return nil, i18n.NewError(ctx, signermsgs.MsgSigningInvalidCompactRSV, len(compactRSV))
+	}
+	var sig SignatureData
+	sig.R = new(big.Int).SetBytes(compactRSV[0:32])
+	sig.S = new(big.Int).SetBytes(compactRSV[32:64])
+	sig.V = new(big.Int).SetBytes(compactRSV[64:65])
+	return &sig, nil
+}
+
 // Sign hashes the input then signs it
 func (k *KeyPair) Sign(message []byte) (ethSig *SignatureData, err error) {
 	msgHash := sha3.NewLegacyKeccak256()