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6c8d40f7 | 1 | /* curve25519-mul-g.c |
28b7678e NM |
2 | |
3 | Copyright (C) 2014 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 | #if HAVE_CONFIG_H | |
33 | # include "config.h" | |
34 | #endif | |
35 | ||
36 | #include <string.h> | |
37 | ||
38 | #include "curve25519.h" | |
39 | ||
40 | #include "ecc.h" | |
41 | #include "ecc-internal.h" | |
42 | ||
43 | /* Intended to be compatible with NaCl's crypto_scalarmult_base. */ | |
44 | void | |
6c8d40f7 | 45 | curve25519_mul_g (uint8_t *r, const uint8_t *n) |
28b7678e | 46 | { |
b1773940 | 47 | const struct ecc_curve *ecc = &_nettle_curve25519; |
28b7678e NM |
48 | uint8_t t[CURVE25519_SIZE]; |
49 | mp_limb_t *scratch; | |
28b7678e NM |
50 | mp_size_t itch; |
51 | ||
a78c9459 NM |
52 | #define ng scratch |
53 | #define x (scratch + 3*ecc->p.size) | |
54 | #define scratch_out (scratch + 4*ecc->p.size) | |
28b7678e NM |
55 | |
56 | memcpy (t, n, sizeof(t)); | |
57 | t[0] &= ~7; | |
58 | t[CURVE25519_SIZE-1] = (t[CURVE25519_SIZE-1] & 0x3f) | 0x40; | |
59 | ||
a78c9459 | 60 | itch = 4*ecc->p.size + ecc->mul_g_itch; |
28b7678e NM |
61 | scratch = gmp_alloc_limbs (itch); |
62 | ||
a78c9459 | 63 | mpn_set_base256_le (x, ecc->p.size, t, CURVE25519_SIZE); |
28b7678e | 64 | |
a78c9459 NM |
65 | ecc_mul_g_eh (ecc, ng, x, scratch_out); |
66 | curve25519_eh_to_x (x, ng, scratch_out); | |
28b7678e | 67 | |
a78c9459 | 68 | mpn_get_base256_le (r, CURVE25519_SIZE, x, ecc->p.size); |
28b7678e | 69 | gmp_free_limbs (scratch, itch); |
51e45744 NM |
70 | #undef p |
71 | #undef x | |
72 | #undef scratch_out | |
28b7678e | 73 | } |