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1 | | /* ecdsa-hash.c |
2 | | |
3 | | Copyright (C) 2013 Niels Möller |
4 | | |
5 | | This file is part of GNU Nettle. |
6 | | |
7 | | GNU Nettle is free software: you can redistribute it and/or |
8 | | modify it under the terms of either: |
9 | | |
10 | | * the GNU Lesser General Public License as published by the Free |
11 | | Software Foundation; either version 3 of the License, or (at your |
12 | | option) any later version. |
13 | | |
14 | | or |
15 | | |
16 | | * the GNU General Public License as published by the Free |
17 | | Software Foundation; either version 2 of the License, or (at your |
18 | | option) any later version. |
19 | | |
20 | | or both in parallel, as here. |
21 | | |
22 | | GNU Nettle is distributed in the hope that it will be useful, |
23 | | but WITHOUT ANY WARRANTY; without even the implied warranty of |
24 | | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
25 | | General Public License for more details. |
26 | | |
27 | | You should have received copies of the GNU General Public License and |
28 | | the GNU Lesser General Public License along with this program. If |
29 | | not, see http://www.gnu.org/licenses/. |
30 | | */ |
31 | | |
32 | | /* Development of Nettle's ECC support was funded by the .SE Internet Fund. */ |
33 | | |
34 | | #if HAVE_CONFIG_H |
35 | | # include "config.h" |
36 | | #endif |
37 | | |
38 | | #include "ecc-internal.h" |
39 | | |
40 | | /* Convert hash value to an integer. If the digest is larger than |
41 | | the ecc bit size, then we must truncate it and use the leftmost |
42 | | bits. */ |
43 | | |
44 | | /* NOTE: We don't considered the hash value to be secret, so it's ok |
45 | | if the running time of this conversion depends on h. |
46 | | |
47 | | Requires m->size + 1 limbs, the extra limb may be needed for |
48 | | unusual limb sizes. |
49 | | */ |
50 | | |
51 | | void |
52 | | ecc_hash (const struct ecc_modulo *m, |
53 | | mp_limb_t *hp, |
54 | | size_t length, const uint8_t *digest) |
55 | 0 | { |
56 | 0 | if (length > ((size_t) m->bit_size + 7) / 8) |
57 | 0 | length = (m->bit_size + 7) / 8; |
58 | |
|
59 | 0 | mpn_set_base256 (hp, m->size + 1, digest, length); |
60 | |
|
61 | 0 | if (8 * length > m->bit_size) |
62 | | /* We got a few extra bits, at the low end. Discard them. */ |
63 | 0 | mpn_rshift (hp, hp, m->size + 1, 8*length - m->bit_size); |
64 | 0 | } |
65 | | |
66 | | void |
67 | | gost_hash (const struct ecc_modulo *m, |
68 | | mp_limb_t *hp, |
69 | | size_t length, const uint8_t *digest) |
70 | 0 | { |
71 | 0 | if (length > ((size_t) m->bit_size + 7) / 8) |
72 | 0 | length = (m->bit_size + 7) / 8; |
73 | |
|
74 | 0 | mpn_set_base256_le (hp, m->size + 1, digest, length); |
75 | 0 | } |