2 * Crypto wrapper for internal crypto implementation - modexp
3 * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
12 #include "tls/bignum.h"
16 int crypto_dh_init(u8 generator, const u8 *prime, size_t prime_len, u8 *privkey,
19 size_t pubkey_len, pad;
21 if (os_get_random(privkey, prime_len) < 0)
23 if (os_memcmp(privkey, prime, prime_len) > 0) {
24 /* Make sure private value is smaller than prime */
28 pubkey_len = prime_len;
29 if (crypto_mod_exp(&generator, 1, privkey, prime_len, prime, prime_len,
30 pubkey, &pubkey_len) < 0)
32 if (pubkey_len < prime_len) {
33 pad = prime_len - pubkey_len;
34 os_memmove(pubkey + pad, pubkey, pubkey_len);
35 os_memset(pubkey, 0, pad);
42 int crypto_dh_derive_secret(u8 generator, const u8 *prime, size_t prime_len,
43 const u8 *privkey, size_t privkey_len,
44 const u8 *pubkey, size_t pubkey_len,
45 u8 *secret, size_t *len)
47 return crypto_mod_exp(pubkey, pubkey_len, privkey, privkey_len,
48 prime, prime_len, secret, len);
52 int crypto_mod_exp(const u8 *base, size_t base_len,
53 const u8 *power, size_t power_len,
54 const u8 *modulus, size_t modulus_len,
55 u8 *result, size_t *result_len)
57 struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result;
60 bn_base = bignum_init();
61 bn_exp = bignum_init();
62 bn_modulus = bignum_init();
63 bn_result = bignum_init();
65 if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL ||
69 if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 ||
70 bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 ||
71 bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0)
74 if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0)
77 ret = bignum_get_unsigned_bin(bn_result, result, result_len);
80 bignum_deinit(bn_base);
81 bignum_deinit(bn_exp);
82 bignum_deinit(bn_modulus);
83 bignum_deinit(bn_result);