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 <tinycrypt/utils.h>
61 #include <string.h>
62
63 #if default_RNG_defined
64 static uECC_RNG_Function g_rng_function = &default_CSPRNG;
65 #else
66 static uECC_RNG_Function g_rng_function = 0;
67 #endif
68
uECC_make_key_with_d(uint8_t * public_key,uint8_t * private_key,unsigned int * d,uECC_Curve curve)69 int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
70 unsigned int *d, uECC_Curve curve)
71 {
72
73 uECC_word_t _private[NUM_ECC_WORDS];
74 uECC_word_t _public[NUM_ECC_WORDS * 2];
75
76 /* This function is designed for test purposes-only (such as validating NIST
77 * test vectors) as it uses a provided value for d instead of generating
78 * it uniformly at random. */
79 memcpy (_private, d, NUM_ECC_BYTES);
80
81 /* Computing public-key from private: */
82 if (EccPoint_compute_public_key(_public, _private, curve)) {
83
84 /* Converting buffers to correct bit order: */
85 uECC_vli_nativeToBytes(private_key,
86 BITS_TO_BYTES(curve->num_n_bits),
87 _private);
88 uECC_vli_nativeToBytes(public_key,
89 curve->num_bytes,
90 _public);
91 uECC_vli_nativeToBytes(public_key + curve->num_bytes,
92 curve->num_bytes,
93 _public + curve->num_words);
94
95 /* erasing temporary buffer used to store secret: */
96 _set_secure(_private, 0, NUM_ECC_BYTES);
97
98 return 1;
99 }
100 return 0;
101 }
102
uECC_make_key(uint8_t * public_key,uint8_t * private_key,uECC_Curve curve)103 int uECC_make_key(uint8_t *public_key, uint8_t *private_key, uECC_Curve curve)
104 {
105
106 uECC_word_t _random[NUM_ECC_WORDS * 2];
107 uECC_word_t _private[NUM_ECC_WORDS];
108 uECC_word_t _public[NUM_ECC_WORDS * 2];
109 uECC_word_t tries;
110
111 for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) {
112 /* Generating _private uniformly at random: */
113 uECC_RNG_Function rng_function = uECC_get_rng();
114 if (!rng_function ||
115 !rng_function((uint8_t *)_random, 2 * NUM_ECC_WORDS * uECC_WORD_SIZE)) {
116 return 0;
117 }
118
119 /* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
120 uECC_vli_mmod(_private, _random, curve->n, BITS_TO_WORDS(curve->num_n_bits));
121
122 /* Computing public-key from private: */
123 if (EccPoint_compute_public_key(_public, _private, curve)) {
124
125 /* Converting buffers to correct bit order: */
126 uECC_vli_nativeToBytes(private_key,
127 BITS_TO_BYTES(curve->num_n_bits),
128 _private);
129 uECC_vli_nativeToBytes(public_key,
130 curve->num_bytes,
131 _public);
132 uECC_vli_nativeToBytes(public_key + curve->num_bytes,
133 curve->num_bytes,
134 _public + curve->num_words);
135
136 /* erasing temporary buffer that stored secret: */
137 _set_secure(_private, 0, NUM_ECC_BYTES);
138
139 return 1;
140 }
141 }
142 return 0;
143 }
144
uECC_shared_secret(const uint8_t * public_key,const uint8_t * private_key,uint8_t * secret,uECC_Curve curve)145 int uECC_shared_secret(const uint8_t *public_key, const uint8_t *private_key,
146 uint8_t *secret, uECC_Curve curve)
147 {
148
149 uECC_word_t _public[NUM_ECC_WORDS * 2];
150 uECC_word_t _private[NUM_ECC_WORDS];
151
152 uECC_word_t tmp[NUM_ECC_WORDS];
153 uECC_word_t *p2[2] = {_private, tmp};
154 uECC_word_t *initial_Z = 0;
155 uECC_word_t carry;
156 wordcount_t num_words = curve->num_words;
157 wordcount_t num_bytes = curve->num_bytes;
158 int r;
159
160 /* Converting buffers to correct bit order: */
161 uECC_vli_bytesToNative(_private,
162 private_key,
163 BITS_TO_BYTES(curve->num_n_bits));
164 uECC_vli_bytesToNative(_public,
165 public_key,
166 num_bytes);
167 uECC_vli_bytesToNative(_public + num_words,
168 public_key + num_bytes,
169 num_bytes);
170
171 /* Regularize the bitcount for the private key so that attackers cannot use a
172 * side channel attack to learn the number of leading zeros. */
173 carry = regularize_k(_private, _private, tmp, curve);
174
175 /* If an RNG function was specified, try to get a random initial Z value to
176 * improve protection against side-channel attacks. */
177 if (g_rng_function) {
178 if (!uECC_generate_random_int(p2[carry], curve->p, num_words)) {
179 r = 0;
180 goto clear_and_out;
181 }
182 initial_Z = p2[carry];
183 }
184
185 EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1,
186 curve);
187
188 uECC_vli_nativeToBytes(secret, num_bytes, _public);
189 r = !EccPoint_isZero(_public, curve);
190
191 clear_and_out:
192 /* erasing temporary buffer used to store secret: */
193 _set_secure(p2, 0, sizeof(p2));
194 _set_secure(tmp, 0, sizeof(tmp));
195 _set_secure(_private, 0, sizeof(_private));
196
197 return r;
198 }
199
