| // SPDX-License-Identifier: BSD-2-Clause |
| /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
| * |
| * LibTomCrypt is a library that provides various cryptographic |
| * algorithms in a highly modular and flexible manner. |
| * |
| * The library is free for all purposes without any express |
| * guarantee it works. |
| */ |
| |
| #include "tomcrypt_private.h" |
| |
| /** |
| @file ecc_shared_secret.c |
| ECC Crypto, Tom St Denis |
| */ |
| |
| #ifdef LTC_MECC |
| |
| /** |
| Create an ECC shared secret between two keys |
| @param private_key The private ECC key |
| @param public_key The public key |
| @param out [out] Destination of the shared secret (Conforms to EC-DH from ANSI X9.63) |
| @param outlen [in/out] The max size and resulting size of the shared secret |
| @return CRYPT_OK if successful |
| */ |
| int ecc_shared_secret(const ecc_key *private_key, const ecc_key *public_key, |
| unsigned char *out, unsigned long *outlen) |
| { |
| unsigned long x; |
| ecc_point *result; |
| void *prime, *a; |
| int err; |
| |
| LTC_ARGCHK(private_key != NULL); |
| LTC_ARGCHK(public_key != NULL); |
| LTC_ARGCHK(out != NULL); |
| LTC_ARGCHK(outlen != NULL); |
| |
| /* type valid? */ |
| if (private_key->type != PK_PRIVATE) { |
| return CRYPT_PK_NOT_PRIVATE; |
| } |
| |
| /* make new point */ |
| result = ltc_ecc_new_point(); |
| if (result == NULL) { |
| return CRYPT_MEM; |
| } |
| |
| prime = private_key->dp.prime; |
| a = private_key->dp.A; |
| |
| if ((err = ltc_mp.ecc_ptmul(private_key->k, &public_key->pubkey, result, a, prime, 1)) != CRYPT_OK) { goto done; } |
| |
| x = (unsigned long)mp_unsigned_bin_size(prime); |
| if (*outlen < x) { |
| *outlen = x; |
| err = CRYPT_BUFFER_OVERFLOW; |
| goto done; |
| } |
| zeromem(out, x); |
| if ((err = mp_to_unsigned_bin(result->x, out + (x - mp_unsigned_bin_size(result->x)))) != CRYPT_OK) { goto done; } |
| |
| err = CRYPT_OK; |
| *outlen = x; |
| done: |
| ltc_ecc_del_point(result); |
| return err; |
| } |
| |
| #endif |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |
| |