// NewSignature generates a ECDSA signature given the raw transaction and privateKey to sign with
func NewSignature(rawTransaction []byte, privateKey []byte) ([]byte, error) {
//Start secp256k1
secp256k1.Start()
var privateKey32 [32]byte
for i := 0; i < 32; i++ {
privateKey32[i] = privateKey[i]
}
//Get the raw public key
publicKey, success := secp256k1.Pubkey_create(privateKey32, false)
if !success {
return nil, errors.New("Failed to create public key from provided private key.")
}
//Hash the raw transaction twice with SHA256 before the signing
shaHash := sha256.New()
shaHash.Write(rawTransaction)
var hash []byte = shaHash.Sum(nil)
shaHash2 := sha256.New()
shaHash2.Write(hash)
rawTransactionHashed := shaHash2.Sum(nil)
//Sign the raw transaction
signedTransaction, success := secp256k1.Sign(rawTransactionHashed, privateKey32, newNonce())
if !success {
return nil, errors.New("Failed to sign transaction")
}
//Verify that it worked.
verified := secp256k1.Verify(rawTransactionHashed, signedTransaction, publicKey)
if !verified {
return nil, errors.New("Failed to verify signed transaction")
}
//Stop secp256k1 and return signature
secp256k1.Stop()
return signedTransaction, nil
}
// NewPublicKey generates the public key from the private key.
// Unfortunately golang ecdsa package does not include a
// secp256k1 curve as this is fairly specific to Bitcoin.
// Using toxeus/go-secp256k1 which wraps the official bitcoin/c-secp256k1 with cgo.
func NewPublicKey(privateKey []byte) ([]byte, error) {
var privateKey32 [32]byte
for i := 0; i < 32; i++ {
privateKey32[i] = privateKey[i]
}
secp256k1.Start()
publicKey, success := secp256k1.Pubkey_create(privateKey32, false)
if !success {
return nil, errors.New("Failed to create public key from provided private key.")
}
secp256k1.Stop()
return publicKey, nil
}