_ Git - BearSSL/blob - 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 }