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crypto, crypto/secp256k1: add CompressPubkey (#15626)

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This adds the inverse to DecompressPubkey and improves a few minor
details in crypto/secp256k1.
This commit is contained in:
Felix Lange
2017-12-15 10:40:09 +01:00
committed by GitHub
parent 1f2176dedc
commit c6069a627c
6 changed files with 118 additions and 52 deletions
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36
crypto/secp256k1/secp256.go
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@ -115,7 +115,7 @@ func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
sigdata = (*C.uchar)(unsafe.Pointer(&sig[0]))
msgdata = (*C.uchar)(unsafe.Pointer(&msg[0]))
)
if C.secp256k1_ecdsa_recover_pubkey(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 {
if C.secp256k1_ext_ecdsa_recover(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 {
return nil, ErrRecoverFailed
}
return pubkey, nil
@ -130,22 +130,42 @@ func VerifySignature(pubkey, msg, signature []byte) bool {
sigdata := (*C.uchar)(unsafe.Pointer(&signature[0]))
msgdata := (*C.uchar)(unsafe.Pointer(&msg[0]))
keydata := (*C.uchar)(unsafe.Pointer(&pubkey[0]))
return C.secp256k1_ecdsa_verify_enc(context, sigdata, msgdata, keydata, C.size_t(len(pubkey))) != 0
return C.secp256k1_ext_ecdsa_verify(context, sigdata, msgdata, keydata, C.size_t(len(pubkey))) != 0
}
// DecompressPubkey parses a public key in the 33-byte compressed format.
// It returns non-nil coordinates if the public key is valid.
func DecompressPubkey(pubkey []byte) (X, Y *big.Int) {
func DecompressPubkey(pubkey []byte) (x, y *big.Int) {
if len(pubkey) != 33 {
return nil, nil
}
buf := make([]byte, 65)
bufdata := (*C.uchar)(unsafe.Pointer(&buf[0]))
pubkeydata := (*C.uchar)(unsafe.Pointer(&pubkey[0]))
if C.secp256k1_decompress_pubkey(context, bufdata, pubkeydata) == 0 {
var (
pubkeydata = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
pubkeylen = C.size_t(len(pubkey))
out = make([]byte, 65)
outdata = (*C.uchar)(unsafe.Pointer(&out[0]))
outlen = C.size_t(len(out))
)
if C.secp256k1_ext_reencode_pubkey(context, outdata, outlen, pubkeydata, pubkeylen) == 0 {
return nil, nil
}
return new(big.Int).SetBytes(buf[1:33]), new(big.Int).SetBytes(buf[33:])
return new(big.Int).SetBytes(out[1:33]), new(big.Int).SetBytes(out[33:])
}
// CompressPubkey encodes a public key to 33-byte compressed format.
func CompressPubkey(x, y *big.Int) []byte {
var (
pubkey = S256().Marshal(x, y)
pubkeydata = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
pubkeylen = C.size_t(len(pubkey))
out = make([]byte, 33)
outdata = (*C.uchar)(unsafe.Pointer(&out[0]))
outlen = C.size_t(len(out))
)
if C.secp256k1_ext_reencode_pubkey(context, outdata, outlen, pubkeydata, pubkeylen) == 0 {
panic("libsecp256k1 error")
}
return out
}
func checkSignature(sig []byte) error {