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Diffstat (limited to 'crypto/secp256k1/libsecp256k1/src/modules/ecdh/main_impl.h')
-rw-r--r-- | crypto/secp256k1/libsecp256k1/src/modules/ecdh/main_impl.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/crypto/secp256k1/libsecp256k1/src/modules/ecdh/main_impl.h b/crypto/secp256k1/libsecp256k1/src/modules/ecdh/main_impl.h new file mode 100644 index 000000000..c23e4f82f --- /dev/null +++ b/crypto/secp256k1/libsecp256k1/src/modules/ecdh/main_impl.h @@ -0,0 +1,54 @@ +/********************************************************************** + * 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_ +#define _SECP256K1_MODULE_ECDH_MAIN_ + +#include "include/secp256k1_ecdh.h" +#include "ecmult_const_impl.h" + +int secp256k1_ecdh(const secp256k1_context* ctx, unsigned char *result, const secp256k1_pubkey *point, const unsigned char *scalar) { + int ret = 0; + int overflow = 0; + secp256k1_gej res; + secp256k1_ge pt; + secp256k1_scalar s; + ARG_CHECK(result != NULL); + ARG_CHECK(point != NULL); + ARG_CHECK(scalar != NULL); + (void)ctx; + + 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[1]; + secp256k1_sha256_t sha; + + secp256k1_ecmult_const(&res, &pt, &s); + secp256k1_ge_set_gej(&pt, &res); + /* Compute a hash of the point in compressed form + * Note we cannot use secp256k1_eckey_pubkey_serialize here since it does not + * expect its output to be secret and has a timing sidechannel. */ + secp256k1_fe_normalize(&pt.x); + secp256k1_fe_normalize(&pt.y); + secp256k1_fe_get_b32(x, &pt.x); + y[0] = 0x02 | secp256k1_fe_is_odd(&pt.y); + + secp256k1_sha256_initialize(&sha); + secp256k1_sha256_write(&sha, y, sizeof(y)); + secp256k1_sha256_write(&sha, x, sizeof(x)); + secp256k1_sha256_finalize(&sha, result); + ret = 1; + } + + secp256k1_scalar_clear(&s); + return ret; +} + +#endif |