68 lines
2.2 KiB
C
68 lines
2.2 KiB
C
/**********************************************************************
|
|
* Copyright (c) 2015 Andrew Poelstra *
|
|
* Distributed under the MIT software license, see the accompanying *
|
|
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
|
|
**********************************************************************/
|
|
|
|
#ifndef SECP256K1_MODULE_ECDH_MAIN_H
|
|
#define SECP256K1_MODULE_ECDH_MAIN_H
|
|
|
|
#include "include/secp256k1_ecdh.h"
|
|
#include "ecmult_const_impl.h"
|
|
|
|
static int ecdh_hash_function_sha256(unsigned char *output, const unsigned char *x, const unsigned char *y, void *data) {
|
|
unsigned char version = (y[31] & 0x01) | 0x02;
|
|
secp256k1_sha256 sha;
|
|
(void)data;
|
|
|
|
secp256k1_sha256_initialize(&sha);
|
|
secp256k1_sha256_write(&sha, &version, 1);
|
|
secp256k1_sha256_write(&sha, x, 32);
|
|
secp256k1_sha256_finalize(&sha, output);
|
|
|
|
return 1;
|
|
}
|
|
|
|
const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_sha256 = ecdh_hash_function_sha256;
|
|
const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_default = ecdh_hash_function_sha256;
|
|
|
|
int secp256k1_ecdh(const secp256k1_context* ctx, unsigned char *output, const secp256k1_pubkey *point, const unsigned char *scalar, secp256k1_ecdh_hash_function hashfp, void *data) {
|
|
int ret = 0;
|
|
int overflow = 0;
|
|
secp256k1_gej res;
|
|
secp256k1_ge pt;
|
|
secp256k1_scalar s;
|
|
VERIFY_CHECK(ctx != NULL);
|
|
ARG_CHECK(output != NULL);
|
|
ARG_CHECK(point != NULL);
|
|
ARG_CHECK(scalar != NULL);
|
|
if (hashfp == NULL) {
|
|
hashfp = secp256k1_ecdh_hash_function_default;
|
|
}
|
|
|
|
secp256k1_pubkey_load(ctx, &pt, point);
|
|
secp256k1_scalar_set_b32(&s, scalar, &overflow);
|
|
if (overflow || secp256k1_scalar_is_zero(&s)) {
|
|
ret = 0;
|
|
} else {
|
|
unsigned char x[32];
|
|
unsigned char y[32];
|
|
|
|
secp256k1_ecmult_const(&res, &pt, &s, 256);
|
|
secp256k1_ge_set_gej(&pt, &res);
|
|
|
|
/* Compute a hash of the point */
|
|
secp256k1_fe_normalize(&pt.x);
|
|
secp256k1_fe_normalize(&pt.y);
|
|
secp256k1_fe_get_b32(x, &pt.x);
|
|
secp256k1_fe_get_b32(y, &pt.y);
|
|
|
|
ret = hashfp(output, x, y, data);
|
|
}
|
|
|
|
secp256k1_scalar_clear(&s);
|
|
return ret;
|
|
}
|
|
|
|
#endif /* SECP256K1_MODULE_ECDH_MAIN_H */
|