// signP2PKHTransaction signs a raw P2PKH transaction, given a private key and the scriptPubKey, inputTx and amount
// to construct the final transaction.
func signP2PKHTransaction(rawTransaction []byte, privateKey []byte, scriptPubKey []byte, inputTx string, amount int) ([]byte, error) {
publicKey, err := btcutils.NewPublicKey(privateKey)
if err != nil {
return nil, err
}
signature, err := btcutils.NewSignature(rawTransaction, privateKey)
if err != nil {
return nil, err
}
hashCodeType, err := hex.DecodeString("01")
if err != nil {
return nil, err
}
//signatureLength is +1 to add hashCodeType
signatureLength := byte(len(signature) + 1)
//Create scriptSig
var buffer bytes.Buffer
buffer.WriteByte(signatureLength)
buffer.Write(signature)
buffer.WriteByte(hashCodeType[0])
buffer.WriteByte(byte(len(publicKey)))
buffer.Write(publicKey)
scriptSig := buffer.Bytes()
//Finally create transaction with actual scriptSig
signedRawTransaction, err := btcutils.NewRawTransaction(inputTx, amount, scriptSig, scriptPubKey)
if err != nil {
return nil, err
}
return signedRawTransaction, nil
}
// signMultisigTransaction signs a raw P2PKH transaction, given slice of private keys and the scriptPubKey, inputTx,
// redeemScript and amount to construct the final transaction.
func signMultisigTransaction(rawTransaction []byte, orderedPrivateKeys [][]byte, scriptPubKey []byte, redeemScript []byte, inputTx string, amount int) ([]byte, error) {
//Hash type SIGHASH_ALL
hashCodeType, err := hex.DecodeString("01")
if err != nil {
return nil, err
}
//Generate signatures for each provided key
signatures := make([][]byte, len(orderedPrivateKeys))
for i, privateKey := range orderedPrivateKeys {
signatures[i], err = btcutils.NewSignature(rawTransaction, privateKey)
if err != nil {
return nil, err
}
}
//redeemScript length. To allow redeemScript > 255 bytes, we use OP_PUSHDATA2 and use two bytes to specify length
var redeemScriptLengthBytes []byte
var requiredOP_PUSHDATA int
if len(redeemScript) < 255 {
requiredOP_PUSHDATA = btcutils.OP_PUSHDATA1 //OP_PUSHDATA1 specifies next *one byte* will be length to be pushed to stack
redeemScriptLengthBytes = []byte{byte(len(redeemScript))}
} else {
requiredOP_PUSHDATA = btcutils.OP_PUSHDATA2 //OP_PUSHDATA2 specifies next *two bytes* will be length to be pushed to stack
redeemScriptLengthBytes = make([]byte, 2)
binary.LittleEndian.PutUint16(redeemScriptLengthBytes, uint16(len(redeemScript)))
}
//Create scriptSig
var buffer bytes.Buffer
buffer.WriteByte(byte(btcutils.OP_0)) //OP_0 for Multisig off-by-one error
for _, signature := range signatures {
buffer.WriteByte(byte(len(signature) + 1)) //PUSH each signature. Add one for hash type byte
buffer.Write(signature) // Signature bytes
buffer.WriteByte(hashCodeType[0]) //hash type
}
buffer.WriteByte(byte(requiredOP_PUSHDATA)) //OP_PUSHDATA1 or OP_PUSHDATA2 depending on size of redeemScript
buffer.Write(redeemScriptLengthBytes) //PUSH redeemScript
buffer.Write(redeemScript) //redeemScript
scriptSig := buffer.Bytes()
//Finally create transaction with actual scriptSig
signedRawTransaction, err := btcutils.NewRawTransaction(inputTx, amount, scriptSig, scriptPubKey)
if err != nil {
return nil, err
}
return signedRawTransaction, nil
}