M common/l1tx.go → common/l1tx.go

@@ -368,18 +368,11 @@
 	return tx, nil
 }
 
-func signHash(data []byte) []byte {
-	msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
-	return ethCrypto.Keccak256([]byte(msg))
-}
-
 // L1CoordinatorTxFromBytes decodes a L1Tx from []byte
 func L1CoordinatorTxFromBytes(b []byte, chainID *big.Int, hermezAddress ethCommon.Address) (*L1Tx, error) {
 	if len(b) != RollupConstL1CoordinatorTotalBytes {
 		return nil, tracerr.Wrap(fmt.Errorf("Can not parse L1CoordinatorTx bytes, expected length %d, current: %d", 101, len(b)))
 	}
-
-	bytesMessage := []byte("I authorize this babyjubjub key for hermez rollup account creation")
 
 	tx := &L1Tx{
 		UserOrigin: false,
@@ -401,18 +394,20 @@ if int(v) > 0 {
 		// L1CoordinatorTX ETH
 		// Ethereum adds 27 to v
 		v = b[0] - byte(27) //nolint:gomnd
-		chainIDBytes := ethCommon.LeftPadBytes(chainID.Bytes(), 2)
-		var data []byte
-		data = append(data, bytesMessage...)
-		data = append(data, pkCompB...)
-		data = append(data, chainIDBytes[:]...)
-		data = append(data, hermezAddress.Bytes()...)
 		var signature []byte
 		signature = append(signature, r[:]...)
 		signature = append(signature, s[:]...)
 		signature = append(signature, v)
-		hash := signHash(data)
-		pubKeyBytes, err := ethCrypto.Ecrecover(hash, signature)
+
+		accCreationAuth := AccountCreationAuth{
+			BJJ: tx.FromBJJ,
+		}
+		h, err := accCreationAuth.HashToSign(uint16(chainID.Uint64()), hermezAddress)
+		if err != nil {
+			return nil, tracerr.Wrap(err)
+		}
+
+		pubKeyBytes, err := ethCrypto.Ecrecover(h, signature)
 		if err != nil {
 			return nil, tracerr.Wrap(err)
 		}

M common/l1tx_test.go → common/l1tx_test.go

@@ -227,7 +227,6 @@
 func TestL1CoordinatorTxByteParsers(t *testing.T) {
 	hermezAddress := ethCommon.HexToAddress("0xD6C850aeBFDC46D7F4c207e445cC0d6B0919BDBe")
 	chainID := big.NewInt(1337)
-	chainIDBytes := ethCommon.LeftPadBytes(chainID.Bytes(), 2)
 
 	privateKey, err := crypto.HexToECDSA("fad9c8855b740a0b7ed4c221dbad0f33a83a49cad6b3fe8d5817ac83d38b6a19")
 	require.NoError(t, err)
@@ -245,18 +244,16 @@ var pkComp babyjub.PublicKeyComp
 	pkCompL := []byte("56ca90f80d7c374ae7485e9bcc47d4ac399460948da6aeeb899311097925a72c")
 	err = pkComp.UnmarshalText(pkCompL)
 	require.NoError(t, err)
-	bytesMessage1 := []byte("\x19Ethereum Signed Message:\n120")
-	bytesMessage2 := []byte("I authorize this babyjubjub key for hermez rollup account creation")
 
-	babyjubB := SwapEndianness(pkComp[:])
-	var data []byte
-	data = append(data, bytesMessage1...)
-	data = append(data, bytesMessage2...)
-	data = append(data, babyjubB[:]...)
-	data = append(data, chainIDBytes...)
-	data = append(data, hermezAddress.Bytes()...)
-	hash := crypto.Keccak256Hash(data)
-	signature, err := crypto.Sign(hash.Bytes(), privateKey)
+	accCreationAuth := AccountCreationAuth{
+		EthAddr: fromEthAddr,
+		BJJ:     pkComp,
+	}
+
+	h, err := accCreationAuth.HashToSign(uint16(chainID.Uint64()), hermezAddress)
+	require.NoError(t, err)
+
+	signature, err := crypto.Sign(h, privateKey)
 	require.NoError(t, err)
 	// Ethereum adds 27 to v
 	v := int(signature[64])