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1 | /* -*-c-*- |
2 | * | |
3 | * Constant-time operations | |
4 | * | |
5 | * (c) 2013 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | /*----- Licensing notice --------------------------------------------------* | |
9 | * | |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
16 | * | |
17 | * Catacomb is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU Library General Public | |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
28 | #ifndef CATACOMB_CT_H | |
29 | #define CATACOMB_CT_H | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
35 | /*----- Header files ------------------------------------------------------*/ | |
36 | ||
37 | #include <mLib/bits.h> | |
38 | ||
39 | /*----- Functions provided ------------------------------------------------*/ | |
40 | ||
41 | /* --- @ct_inteq@ --- * | |
42 | * | |
43 | * Arguments: @uint32 x, y@ = two 32-bit unsigned integers | |
44 | * | |
45 | * Returns: One if @x@ and @y@ are equal, zero if they differ. | |
46 | * | |
47 | * Use: Answers whether two integers are equal, in constant time. | |
48 | */ | |
49 | ||
50 | extern int ct_inteq(uint32 /*x*/, uint32 /*y*/); | |
51 | ||
52 | /* --- @ct_intle@ --- * | |
53 | * | |
54 | * Arguments: @uint32 x, y@ = two 32-bit unsigned integers | |
55 | * | |
c4377d0e | 56 | * Returns: One if %$x \le y$%, zero if @x@ is greater. |
d4bb7fde MW |
57 | * |
58 | * Use: Answers whether two integers are ordered, in constant time. | |
59 | */ | |
60 | ||
61 | extern int ct_intle(uint32 /*x*/, uint32 /*y*/); | |
62 | ||
63 | /* --- @ct_pick@ --- * | |
64 | * | |
65 | * Arguments: @uint32 a@ = a switch, either zero or one | |
66 | * @uint32 x0, x1@ = two 32-bit unsigned integers | |
67 | * | |
68 | * Returns: @x0@ if @a@ is zero; @x1@ if @a@ is one. Other values of @a@ | |
69 | * will give you unhelpful results. | |
70 | * | |
71 | * Use: Picks one of two results according to a switch variable, in | |
72 | * constant time. | |
73 | */ | |
74 | ||
75 | extern int ct_pick(uint32 /*a*/, uint32 /*x0*/, uint32 /*x1*/); | |
76 | ||
77 | /* --- @ct_condcopy@ --- * | |
78 | * | |
79 | * Arguments: @uint32 a@ = a switch, either zero or one | |
80 | * @void *d@ = destination pointer | |
81 | * @const void *s@ = source pointer | |
82 | * @size_t n@ amount to copy | |
83 | * | |
84 | * Returns: --- | |
85 | * | |
86 | * Use: If @a@ is one then copy the @n@ bytes starting at @s@ to | |
87 | * @d@; if @a@ is zero then leave @d@ unchanged (but it will | |
88 | * still be written). All of this is done in constant time. | |
89 | */ | |
90 | ||
91 | extern void ct_condcopy(uint32 /*a*/, | |
92 | void */*d*/, const void */*s*/, size_t /*n*/); | |
93 | ||
94 | /* --- @ct_memeq@ --- | |
95 | * | |
96 | * Arguments: @const void *p, *q@ = two pointers to buffers | |
97 | * @size_t n@ = the (common) size of the buffers | |
98 | * | |
99 | * Returns: One if the two buffers are equal, zero if they aren't. | |
100 | * | |
101 | * Use: Compares two chunks of memory, in constant time. | |
102 | */ | |
103 | ||
104 | extern int ct_memeq(const void */*p*/, const void */*q*/, size_t /*n*/); | |
105 | ||
106 | /*----- That's all, folks -------------------------------------------------*/ | |
107 | ||
108 | #ifdef __cplusplus | |
109 | } | |
110 | #endif | |
111 | ||
112 | #endif |