Some documentation fixes.
[BearSSL] / src / symcipher / aes_small_enc.c
1 /*
2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 #define S br_aes_S
28
29 static void
30 add_round_key(unsigned *state, const uint32_t *skeys)
31 {
32 int i;
33
34 for (i = 0; i < 16; i += 4) {
35 uint32_t k;
36
37 k = *skeys ++;
38 state[i + 0] ^= (unsigned)(k >> 24);
39 state[i + 1] ^= (unsigned)(k >> 16) & 0xFF;
40 state[i + 2] ^= (unsigned)(k >> 8) & 0xFF;
41 state[i + 3] ^= (unsigned)k & 0xFF;
42 }
43 }
44
45 static void
46 sub_bytes(unsigned *state)
47 {
48 int i;
49
50 for (i = 0; i < 16; i ++) {
51 state[i] = S[state[i]];
52 }
53 }
54
55 static void
56 shift_rows(unsigned *state)
57 {
58 unsigned tmp;
59
60 tmp = state[1];
61 state[1] = state[5];
62 state[5] = state[9];
63 state[9] = state[13];
64 state[13] = tmp;
65
66 tmp = state[2];
67 state[2] = state[10];
68 state[10] = tmp;
69 tmp = state[6];
70 state[6] = state[14];
71 state[14] = tmp;
72
73 tmp = state[15];
74 state[15] = state[11];
75 state[11] = state[7];
76 state[7] = state[3];
77 state[3] = tmp;
78 }
79
80 static void
81 mix_columns(unsigned *state)
82 {
83 int i;
84
85 for (i = 0; i < 16; i += 4) {
86 unsigned s0, s1, s2, s3;
87 unsigned t0, t1, t2, t3;
88
89 s0 = state[i + 0];
90 s1 = state[i + 1];
91 s2 = state[i + 2];
92 s3 = state[i + 3];
93 t0 = (s0 << 1) ^ s1 ^ (s1 << 1) ^ s2 ^ s3;
94 t1 = s0 ^ (s1 << 1) ^ s2 ^ (s2 << 1) ^ s3;
95 t2 = s0 ^ s1 ^ (s2 << 1) ^ s3 ^ (s3 << 1);
96 t3 = s0 ^ (s0 << 1) ^ s1 ^ s2 ^ (s3 << 1);
97 state[i + 0] = t0 ^ ((unsigned)(-(int)(t0 >> 8)) & 0x11B);
98 state[i + 1] = t1 ^ ((unsigned)(-(int)(t1 >> 8)) & 0x11B);
99 state[i + 2] = t2 ^ ((unsigned)(-(int)(t2 >> 8)) & 0x11B);
100 state[i + 3] = t3 ^ ((unsigned)(-(int)(t3 >> 8)) & 0x11B);
101 }
102 }
103
104 /* see inner.h */
105 void
106 br_aes_small_encrypt(unsigned num_rounds, const uint32_t *skey, void *data)
107 {
108 unsigned char *buf;
109 unsigned state[16];
110 unsigned u;
111
112 buf = data;
113 for (u = 0; u < 16; u ++) {
114 state[u] = buf[u];
115 }
116 add_round_key(state, skey);
117 for (u = 1; u < num_rounds; u ++) {
118 sub_bytes(state);
119 shift_rows(state);
120 mix_columns(state);
121 add_round_key(state, skey + (u << 2));
122 }
123 sub_bytes(state);
124 shift_rows(state);
125 add_round_key(state, skey + (num_rounds << 2));
126 for (u = 0; u < 16; u ++) {
127 buf[u] = state[u];
128 }
129 }