3 Copyright (C) 2013 Niels Möller
5 This file is part of GNU Nettle.
7 GNU Nettle is free software: you can redistribute it and/or
8 modify it under the terms of either:
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.
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.
20 or both in parallel, as here.
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.
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/.
32 /* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
38 #include "ecc-internal.h"
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
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.
47 Requires m->size + 1 limbs, the extra limb may be needed for
52 ecc_hash (const struct ecc_modulo *m,
54 size_t length, const uint8_t *digest)
56 if (length > ((size_t) m->bit_size + 7) / 8)
57 length = (m->bit_size + 7) / 8;
59 mpn_set_base256 (hp, m->size + 1, digest, length);
61 if (8 * length > m->bit_size)
62 /* We got a few extra bits, at the low end. Discard them. */
63 mpn_rshift (hp, hp, m->size + 1, 8*length - m->bit_size);