_ Git - BearSSL/blob - src/symcipher/aes_ct64_dec.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 /* see inner.h */
  28 void
  29 br_aes_ct64_bitslice_invSbox(uint64_t *q)
  30 {
  31         /*
  32          * See br_aes_ct_bitslice_invSbox(). This is the natural extension
  33          * to 64-bit registers.
  34          */
  35         uint64_t q0, q1, q2, q3, q4, q5, q6, q7;
  36
  37         q0 = ~q[0];
  38         q1 = ~q[1];
  39         q2 = q[2];
  40         q3 = q[3];
  41         q4 = q[4];
  42         q5 = ~q[5];
  43         q6 = ~q[6];
  44         q7 = q[7];
  45         q[7] = q1 ^ q4 ^ q6;
  46         q[6] = q0 ^ q3 ^ q5;
  47         q[5] = q7 ^ q2 ^ q4;
  48         q[4] = q6 ^ q1 ^ q3;
  49         q[3] = q5 ^ q0 ^ q2;
  50         q[2] = q4 ^ q7 ^ q1;
  51         q[1] = q3 ^ q6 ^ q0;
  52         q[0] = q2 ^ q5 ^ q7;
  53
  54         br_aes_ct64_bitslice_Sbox(q);
  55
  56         q0 = ~q[0];
  57         q1 = ~q[1];
  58         q2 = q[2];
  59         q3 = q[3];
  60         q4 = q[4];
  61         q5 = ~q[5];
  62         q6 = ~q[6];
  63         q7 = q[7];
  64         q[7] = q1 ^ q4 ^ q6;
  65         q[6] = q0 ^ q3 ^ q5;
  66         q[5] = q7 ^ q2 ^ q4;
  67         q[4] = q6 ^ q1 ^ q3;
  68         q[3] = q5 ^ q0 ^ q2;
  69         q[2] = q4 ^ q7 ^ q1;
  70         q[1] = q3 ^ q6 ^ q0;
  71         q[0] = q2 ^ q5 ^ q7;
  72 }
  73
  74 static void
  75 add_round_key(uint64_t *q, const uint64_t *sk)
  76 {
  77         int i;
  78
  79         for (i = 0; i < 8; i ++) {
  80                 q[i] ^= sk[i];
  81         }
  82 }
  83
  84 static void
  85 inv_shift_rows(uint64_t *q)
  86 {
  87         int i;
  88
  89         for (i = 0; i < 8; i ++) {
  90                 uint64_t x;
  91
  92                 x = q[i];
  93                 q[i] = (x & (uint64_t)0x000000000000FFFF)
  94                         | ((x & (uint64_t)0x000000000FFF0000) << 4)
  95                         | ((x & (uint64_t)0x00000000F0000000) >> 12)
  96                         | ((x & (uint64_t)0x000000FF00000000) << 8)
  97                         | ((x & (uint64_t)0x0000FF0000000000) >> 8)
  98                         | ((x & (uint64_t)0x000F000000000000) << 12)
  99                         | ((x & (uint64_t)0xFFF0000000000000) >> 4);
 100         }
 101 }
 102
 103 static inline uint64_t
 104 rotr32(uint64_t x)
 105 {
 106         return (x << 32) | (x >> 32);
 107 }
 108
 109 static void
 110 inv_mix_columns(uint64_t *q)
 111 {
 112         uint64_t q0, q1, q2, q3, q4, q5, q6, q7;
 113         uint64_t r0, r1, r2, r3, r4, r5, r6, r7;
 114
 115         q0 = q[0];
 116         q1 = q[1];
 117         q2 = q[2];
 118         q3 = q[3];
 119         q4 = q[4];
 120         q5 = q[5];
 121         q6 = q[6];
 122         q7 = q[7];
 123         r0 = (q0 >> 16) | (q0 << 48);
 124         r1 = (q1 >> 16) | (q1 << 48);
 125         r2 = (q2 >> 16) | (q2 << 48);
 126         r3 = (q3 >> 16) | (q3 << 48);
 127         r4 = (q4 >> 16) | (q4 << 48);
 128         r5 = (q5 >> 16) | (q5 << 48);
 129         r6 = (q6 >> 16) | (q6 << 48);
 130         r7 = (q7 >> 16) | (q7 << 48);
 131
 132         q[0] = q5 ^ q6 ^ q7 ^ r0 ^ r5 ^ r7 ^ rotr32(q0 ^ q5 ^ q6 ^ r0 ^ r5);
 133         q[1] = q0 ^ q5 ^ r0 ^ r1 ^ r5 ^ r6 ^ r7 ^ rotr32(q1 ^ q5 ^ q7 ^ r1 ^ r5 ^ r6);
 134         q[2] = q0 ^ q1 ^ q6 ^ r1 ^ r2 ^ r6 ^ r7 ^ rotr32(q0 ^ q2 ^ q6 ^ r2 ^ r6 ^ r7);
 135         q[3] = q0 ^ q1 ^ q2 ^ q5 ^ q6 ^ r0 ^ r2 ^ r3 ^ r5 ^ rotr32(q0 ^ q1 ^ q3 ^ q5 ^ q6 ^ q7 ^ r0 ^ r3 ^ r5 ^ r7);
 136         q[4] = q1 ^ q2 ^ q3 ^ q5 ^ r1 ^ r3 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr32(q1 ^ q2 ^ q4 ^ q5 ^ q7 ^ r1 ^ r4 ^ r5 ^ r6);
 137         q[5] = q2 ^ q3 ^ q4 ^ q6 ^ r2 ^ r4 ^ r5 ^ r6 ^ r7 ^ rotr32(q2 ^ q3 ^ q5 ^ q6 ^ r2 ^ r5 ^ r6 ^ r7);
 138         q[6] = q3 ^ q4 ^ q5 ^ q7 ^ r3 ^ r5 ^ r6 ^ r7 ^ rotr32(q3 ^ q4 ^ q6 ^ q7 ^ r3 ^ r6 ^ r7);
 139         q[7] = q4 ^ q5 ^ q6 ^ r4 ^ r6 ^ r7 ^ rotr32(q4 ^ q5 ^ q7 ^ r4 ^ r7);
 140 }
 141
 142 /* see inner.h */
 143 void
 144 br_aes_ct64_bitslice_decrypt(unsigned num_rounds,
 145         const uint64_t *skey, uint64_t *q)
 146 {
 147         unsigned u;
 148
 149         add_round_key(q, skey + (num_rounds << 3));
 150         for (u = num_rounds - 1; u > 0; u --) {
 151                 inv_shift_rows(q);
 152                 br_aes_ct64_bitslice_invSbox(q);
 153                 add_round_key(q, skey + (u << 3));
 154                 inv_mix_columns(q);
 155         }
 156         inv_shift_rows(q);
 157         br_aes_ct64_bitslice_invSbox(q);
 158         add_round_key(q, skey);
 159 }