package secp256k1
/*
#cgo CFLAGS: -std=gnu99 -Wno-error
#cgo darwin CFLAGS: -I/usr/local/include
#cgo LDFLAGS: -lgmp
#cgo darwin LDFLAGS: -L/usr/local/lib
#define USE_FIELD_10X26
#define USE_NUM_GMP
#define USE_FIELD_INV_BUILTIN
#include "./secp256k1/src/secp256k1.c"
*/
import "C"
import (
"bytes"
"errors"
"unsafe"
)
//#define USE_FIELD_5X64
/*
Todo:
> Centralize key management in module
> add pubkey/private key struct
> Dont let keys leave module; address keys as ints
> store private keys in buffer and shuffle (deters persistance on swap disc)
> Byte permutation (changing)
> xor with chaning random block (to deter scanning memory for 0x63) (stream cipher?)
On Disk
> Store keys in wallets
> use slow key derivation function for wallet encryption key (2 seconds)
*/
func init() {
C.secp256k1_start() //takes 10ms to 100ms
}
func Stop() {
C.secp256k1_stop()
}
/*
int secp256k1_ecdsa_pubkey_create(
unsigned char *pubkey, int *pubkeylen,
const unsigned char *seckey, int compressed);
*/
/** Compute the public key for a secret key.
* In: compressed: whether the computed public key should be compressed
* seckey: pointer to a 32-byte private key.
* Out: pubkey: pointer to a 33-byte (if compressed) or 65-byte (if uncompressed)
* area to store the public key.
* pubkeylen: pointer to int that will be updated to contains the pubkey's
* length.
* Returns: 1: secret was valid, public key stores
* 0: secret was invalid, try again.
*/
//pubkey, seckey
func GenerateKeyPair() ([]byte, []byte) {
pubkey_len := C.int(65)
const seckey_len = 32
var pubkey []byte = make([]byte, pubkey_len)
var seckey []byte = RandByte(seckey_len)
var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
ret := C.secp256k1_ecdsa_pubkey_create(
pubkey_ptr, &pubkey_len,
seckey_ptr, 0)
if ret != C.int(1) {
return GenerateKeyPair() //invalid secret, try again
}
return pubkey, seckey
}
func GeneratePubKey(seckey []byte) ([]byte, error) {
pubkey_len := C.int(65)
const seckey_len = 32
var pubkey []byte = make([]byte, pubkey_len)
var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
ret := C.secp256k1_ecdsa_pubkey_create(
pubkey_ptr, &pubkey_len,
seckey_ptr, 0)
if ret != C.int(1) {
return nil, errors.New("Unable to generate pubkey from seckey")
}
return pubkey, nil
}
/*
* Create a compact ECDSA signature (64 byte + recovery id).
* Returns: 1: signature created
* 0: nonce invalid, try another one
* In: msg: the message being signed
* msglen: the length of the message being signed
* seckey: pointer to a 32-byte secret key (assumed to be valid)
* nonce: pointer to a 32-byte nonce (generated with a cryptographic PRNG)
* Out: sig: pointer to a 64-byte array where the signature will be placed.
* recid: pointer to an int, which will be updated to contain the recovery id.
*/
/*
int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
unsigned char *sig64,
const unsigned char *seckey,
const unsigned char *nonce,
int *recid);
*/
func Sign(msg []byte, seckey []byte) ([]byte, error) {
nonce := RandByte(32)
var sig []byte = make([]byte, 65)
var recid C.int
var msg_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&msg[0]))
var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
var nonce_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&nonce[0]))
var sig_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&sig[0]))
if C.secp256k1_ecdsa_seckey_verify(seckey_ptr) != C.int(1) {
return nil, errors.New("Invalid secret key")
}
ret := C.secp256k1_ecdsa_sign_compact(
msg_ptr, C.int(len(msg)),
sig_ptr,
seckey_ptr,
nonce_ptr,
&recid)
sig[64] = byte(int(recid))
if ret != C.int(1) {
// nonce invalid, retry
return Sign(msg, seckey)
}
return sig, nil
}
/*
* Verify an ECDSA secret key.
* Returns: 1: secret key is valid
* 0: secret key is invalid
* In: seckey: pointer to a 32-byte secret key
*/
func VerifySeckeyValidity(seckey []byte) error {
if len(seckey) != 32 {
return errors.New("priv key is not 32 bytes")
}
var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
ret := C.secp256k1_ecdsa_seckey_verify(seckey_ptr)
if int(ret) != 1 {
return errors.New("invalid seckey")
}
return nil
}
/*
* Validate a public key.
* Returns: 1: valid public key
* 0: invalid public key
*/
func VerifyPubkeyValidity(pubkey []byte) error {
if len(pubkey) != 65 {
return errors.New("pub key is not 65 bytes")
}
var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
ret := C.secp256k1_ecdsa_pubkey_verify(pubkey_ptr, 65)
if int(ret) != 1 {
return errors.New("invalid pubkey")
}
return nil
}
func VerifySignatureValidity(sig []byte) bool {
//64+1
if len(sig) != 65 {
return false
}
//malleability check, highest bit must be 1
if (sig[32] & 0x80) == 0x80 {
return false
}
//recovery id check
if sig[64] >= 4 {
return false
}
return true
}
//for compressed signatures, does not need pubkey
func VerifySignature(msg []byte, sig []byte, pubkey1 []byte) error {
if msg == nil || sig == nil || pubkey1 == nil {
return errors.New("inputs must be non-nil")
}
if len(sig) != 65 {
return errors.New("invalid signature length")
}
if len(pubkey1) != 65 {
return errors.New("Invalid public key length")
}
//to enforce malleability, highest bit of S must be 0
//S starts at 32nd byte
if (sig[32] & 0x80) == 0x80 { //highest bit must be 1
return errors.New("Signature not malleable")
}
if sig[64] >= 4 {
return errors.New("Recover byte invalid")
}
// if pubkey recovered, signature valid
pubkey2, err := RecoverPubkey(msg, sig)
if err != nil {
return err
}
if len(pubkey2) != 65 {
return errors.New("Invalid recovered public key length")
}
if !bytes.Equal(pubkey1, pubkey2) {
return errors.New("Public key does not match recovered public key")
}
return nil
}
/*
int secp256k1_ecdsa_recover_compact(const unsigned char *msg, int msglen,
const unsigned char *sig64,
unsigned char *pubkey, int *pubkeylen,
int compressed, int recid);
*/
/*
* Recover an ECDSA public key from a compact signature.
* Returns: 1: public key succesfully recovered (which guarantees a correct signature).
* 0: otherwise.
* In: msg: the message assumed to be signed
* msglen: the length of the message
* compressed: whether to recover a compressed or uncompressed pubkey
* recid: the recovery id (as returned by ecdsa_sign_compact)
* Out: pubkey: pointer to a 33 or 65 byte array to put the pubkey.
* pubkeylen: pointer to an int that will contain the pubkey length.
*/
//recovers the public key from the signature
//recovery of pubkey means correct signature
func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
if len(sig) != 65 {
return nil, errors.New("Invalid signature length")
}
var pubkey []byte = make([]byte, 65)
var msg_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&msg[0]))
var sig_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&sig[0]))
var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
var pubkeylen C.int
ret := C.secp256k1_ecdsa_recover_compact(
msg_ptr, C.int(len(msg)),
sig_ptr,
pubkey_ptr, &pubkeylen,
C.int(0), C.int(sig[64]),
)
if ret == C.int(0) {
return nil, errors.New("Failed to recover public key")
} else if pubkeylen != C.int(65) {
return nil, errors.New("Impossible Error: Invalid recovered public key length")
} else {
return pubkey, nil
}
return nil, errors.New("Impossible Error: func RecoverPubkey has reached an unreachable state")
}
