1 /*
2 * Copyright (C) 2020 Olivier Chéron <olivier.cheron@gmail.com>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25 #ifndef CRYPTONITE_HASH_PREFIX_H
26 #define CRYPTONITE_HASH_PREFIX_H
27
28 #include <stdint.h>
29
constant_time_msb(uint32_t a)30 static inline uint32_t constant_time_msb(uint32_t a)
31 {
32 return 0 - (a >> 31);
33 }
34
constant_time_lt(uint32_t a,uint32_t b)35 static inline uint32_t constant_time_lt(uint32_t a, uint32_t b)
36 {
37 return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b)));
38 }
39
constant_time_ge(uint32_t a,uint32_t b)40 static inline uint32_t constant_time_ge(uint32_t a, uint32_t b)
41 {
42 return ~constant_time_lt(a, b);
43 }
44
constant_time_is_zero(uint32_t a)45 static inline uint32_t constant_time_is_zero(uint32_t a)
46 {
47 return constant_time_msb(~a & (a - 1));
48 }
49
constant_time_eq(uint32_t a,uint32_t b)50 static inline uint32_t constant_time_eq(uint32_t a, uint32_t b)
51 {
52 return constant_time_is_zero(a ^ b);
53 }
54
constant_time_msb_64(uint64_t a)55 static inline uint64_t constant_time_msb_64(uint64_t a)
56 {
57 return 0 - (a >> 63);
58 }
59
constant_time_lt_64(uint64_t a,uint64_t b)60 static inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b)
61 {
62 return constant_time_msb_64(a ^ ((a ^ b) | ((a - b) ^ b)));
63 }
64
65 #endif
66