1 /* ec_dh.c - TinyCrypt implementation of EC-DH */
2
3 /*
4 * Copyright (c) 2014, Kenneth MacKay
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * * Redistributions of source code must retain the above copyright notice,
10 * this list of conditions and the following disclaimer.
11 * * Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
19 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 * POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 /*
29 * Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
30 *
31 * Redistribution and use in source and binary forms, with or without
32 * modification, are permitted provided that the following conditions are met:
33 *
34 * - Redistributions of source code must retain the above copyright notice,
35 * this list of conditions and the following disclaimer.
36 *
37 * - Redistributions in binary form must reproduce the above copyright
38 * notice, this list of conditions and the following disclaimer in the
39 * documentation and/or other materials provided with the distribution.
40 *
41 * - Neither the name of Intel Corporation nor the names of its contributors
42 * may be used to endorse or promote products derived from this software
43 * without specific prior written permission.
44 *
45 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
46 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
47 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
48 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
49 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
50 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
51 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
52 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
53 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
54 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
55 * POSSIBILITY OF SUCH DAMAGE.
56 */
57 #include <tinycrypt/constants.h>
58 #include <tinycrypt/ecc.h>
59 #include <tinycrypt/ecc_dh.h>
60 #include <string.h>
61
62 #if default_RNG_defined
63 static uECC_RNG_Function g_rng_function = &default_CSPRNG;
64 #else
65 static uECC_RNG_Function g_rng_function = 0;
66 #endif
67
uECC_make_key_with_d(uint8_t * public_key,uint8_t * private_key,unsigned int * d,uECC_Curve curve)68 int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
69 unsigned int *d, uECC_Curve curve)
70 {
71 uECC_word_t _private[NUM_ECC_WORDS];
72 uECC_word_t _public[NUM_ECC_WORDS * 2];
73 /* This function is designed for test purposes-only (such as validating NIST
74 * test vectors) as it uses a provided value for d instead of generating
75 * it uniformly at random. */
76 memcpy_s(_private, sizeof(_private), d, NUM_ECC_BYTES);
77
78 /* Computing public-key from private: */
79 if (EccPoint_compute_public_key(_public, _private, curve)) {
80 /* Converting buffers to correct bit order: */
81 uECC_vli_nativeToBytes(private_key,
82 BITS_TO_BYTES(curve->num_n_bits),
83 _private);
84 uECC_vli_nativeToBytes(public_key,
85 curve->num_bytes,
86 _public);
87 uECC_vli_nativeToBytes(public_key + curve->num_bytes,
88 curve->num_bytes,
89 _public + curve->num_words);
90 /* erasing temporary buffer used to store secret: */
91 memset_s(_private, sizeof(_private), 0, NUM_ECC_BYTES);
92 return 1;
93 }
94
95 return 0;
96 }
97
uECC_make_key(uint8_t * public_key,uint8_t * private_key,uECC_Curve curve)98 int uECC_make_key(uint8_t *public_key, uint8_t *private_key, uECC_Curve curve)
99 {
100 uECC_word_t _random[NUM_ECC_WORDS * 2];
101 uECC_word_t _private[NUM_ECC_WORDS];
102 uECC_word_t _public[NUM_ECC_WORDS * 2];
103 uECC_word_t tries;
104
105 for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) {
106 /* Generating _private uniformly at random: */
107 uECC_RNG_Function rng_function = uECC_get_rng();
108 if (!rng_function ||
109 !rng_function((uint8_t *)_random, 2 * NUM_ECC_WORDS * uECC_WORD_SIZE)) { // 2:byte alignment
110 return 0;
111 }
112
113 /* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
114 uECC_vli_mmod(_private, _random, curve->n, BITS_TO_WORDS(curve->num_n_bits));
115
116 /* Computing public-key from private: */
117 if (EccPoint_compute_public_key(_public, _private, curve)) {
118 /* Converting buffers to correct bit order: */
119 uECC_vli_nativeToBytes(private_key,
120 BITS_TO_BYTES(curve->num_n_bits),
121 _private);
122 uECC_vli_nativeToBytes(public_key,
123 curve->num_bytes,
124 _public);
125 uECC_vli_nativeToBytes(public_key + curve->num_bytes,
126 curve->num_bytes,
127 _public + curve->num_words);
128 /* erasing temporary buffer that stored secret: */
129 memset_s(_private, sizeof(_private), 0, NUM_ECC_BYTES);
130 return 1;
131 }
132 }
133
134 return 0;
135 }
136
uECC_shared_secret(const uint8_t * public_key,const uint8_t * private_key,uint8_t * secret,uECC_Curve curve)137 int uECC_shared_secret(const uint8_t *public_key, const uint8_t *private_key,
138 uint8_t *secret, uECC_Curve curve)
139 {
140 uECC_word_t _public[NUM_ECC_WORDS * 2];
141 uECC_word_t _private[NUM_ECC_WORDS];
142 uECC_word_t tmp[NUM_ECC_WORDS];
143 uECC_word_t *p2[2] = {_private, tmp};
144 uECC_word_t *initial_Z = 0;
145 uECC_word_t carry;
146 wordcount_t num_words = curve->num_words;
147 wordcount_t num_bytes = curve->num_bytes;
148 int r;
149 /* Converting buffers to correct bit order: */
150 uECC_vli_bytesToNative(_private,
151 private_key,
152 BITS_TO_BYTES(curve->num_n_bits));
153 uECC_vli_bytesToNative(_public,
154 public_key,
155 num_bytes);
156 uECC_vli_bytesToNative(_public + num_words,
157 public_key + num_bytes,
158 num_bytes);
159 /* Regularize the bitcount for the private key so that attackers cannot use a
160 * side channel attack to learn the number of leading zeros. */
161 carry = regularize_k(_private, _private, tmp, curve);
162
163 /* If an RNG function was specified, try to get a random initial Z value to
164 * improve protection against side-channel attacks. */
165 if (g_rng_function) {
166 if (!uECC_generate_random_int(p2[carry], curve->p, num_words)) {
167 r = 0;
168 goto clear_and_out;
169 }
170
171 initial_Z = p2[carry];
172 }
173
174 EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1,
175 curve);
176 uECC_vli_nativeToBytes(secret, num_bytes, _public);
177 r = !EccPoint_isZero(_public, curve);
178 clear_and_out:
179 /* erasing temporary buffer used to store secret: */
180 memset_s(p2, sizeof(p2), 0, sizeof(p2));
181 __asm__ __volatile__("" :: "g"(p2) : "memory");
182 memset_s(tmp, sizeof(tmp), 0, sizeof(tmp));
183 __asm__ __volatile__("" :: "g"(tmp) : "memory");
184 memset_s(_private, sizeof(_private), 0, sizeof(_private));
185 __asm__ __volatile__("" :: "g"(_private) : "memory");
186 return r;
187 }
188