chiark - git - mdw - catacomb/blob - symm/rc5.c

   1 /* -*-c-*-
   2  *
   3  * The RC5-32/12 block cipher
   4  *
   5  * (c) 1999 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 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <assert.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #include <mLib/alloc.h>
  35 #include <mLib/bits.h>
  36
  37 #include "arena.h"
  38 #include "blkc.h"
  39 #include "gcipher.h"
  40 #include "rc5.h"
  41
  42 /*----- Global variables --------------------------------------------------*/
  43
  44 const octet rc5_keysz[] = { KSZ_RANGE, RC5_KEYSZ, 1, 255, 1 };
  45
  46 /*----- Internal magical constants ----------------------------------------*/
  47
  48 #define T ((RC5_ROUNDS + 1) * 2)
  49 #define P 0xb7e15163
  50 #define Q 0x9e3779b9
  51
  52 /*----- Main code ---------------------------------------------------------*/
  53
  54 /* --- @rc5_init@ --- *
  55  *
  56  * Arguments:   @rc5_ctx *k@ = pointer to a key block
  57  *              @const void *sbuf@ = pointer to key material
  58  *              @size_t sz@ = size of the key material
  59  *
  60  * Returns:     ---
  61  *
  62  * Use:         Initializes an RC5 key block.
  63  */
  64
  65 void rc5_init(rc5_ctx *k, const void *sbuf, size_t sz)
  66 {
  67   uint32 *l;
  68   size_t w;
  69
  70   /* --- Set up the @L@ table --- *
  71    *
  72    * This is slightly unfortunately defined.
  73    */
  74
  75   KSZ_ASSERT(rc5, sz);
  76
  77   {
  78     int i;
  79     const octet *p = sbuf;
  80
  81     /* --- Create the buffer --- */
  82
  83     w = (sz + 3) / 4;
  84     l = XS_ALLOC(w * sizeof(uint32));
  85
  86     /* --- Extract the key material --- */
  87
  88     for (i = 0; sz > 3; i++) {
  89       l[i] = LOAD32_L(p);
  90       p += 4;
  91       sz -= 4;
  92     }
  93
  94     /* --- Fix up the tail end --- */
  95
  96     if (sz) {
  97       uint32 x = U8(*p++);
  98       if (sz > 1) x |= (U8(*p++) <<  8);
  99       if (sz > 2) x |= (U8(*p++) << 16);
 100       l[i] = x;
 101     }
 102   }
 103
 104   /* --- Initialize the @S@ table --- */
 105
 106   {
 107     int i;
 108
 109     k->s[0] = P;
 110     for (i = 1; i < T; i++)
 111       k->s[i] = k->s[i - 1] + Q;
 112   }
 113
 114   /* --- Mix in the key --- */
 115
 116   {
 117     int m = 3 * (w > T ? w : T);
 118     int i, j, c;
 119     uint32 a, b;
 120
 121     for (c = i = j = a = b = 0; c < m; c++) {
 122       uint32 x;
 123
 124       x = k->s[i] + a + b;
 125       k->s[i] = a = ROL32(x, 3);
 126       i++; if (i >= T) i = 0;
 127
 128       x = l[j] + a + b;
 129       l[j] = b = ROL32(x, a + b);
 130       j++; if (j >= w) j = 0;
 131     }
 132   }
 133
 134   memset(l, 0, w * sizeof(uint32));
 135   XS_FREE(l);
 136 }
 137
 138 /* --- @EROUND@, @DROUND@ --- */
 139
 140 #define EROUND(x, y, k) do {                                            \
 141   uint32 _x;                                                            \
 142   _x = x ^ y; x = ROL32(_x, y) + k[0];                                  \
 143   _x = y ^ x; y = ROL32(_x, x) + k[1];                                  \
 144   k += 2;                                                               \
 145 } while (0)
 146
 147 #define DROUND(x, y, k) do {                                            \
 148   uint32 _x;                                                            \
 149   k -= 2;                                                               \
 150   _x = y - k[1]; y = ROR32(_x, x) ^ x;                                  \
 151   _x = x - k[0]; x = ROR32(_x, y) ^ y;                                  \
 152 } while (0)
 153
 154 /* --- @EBLK@, @DBLK@ --- */
 155
 156 #define EBLK(a, b, c, d, k) do {                                        \
 157   uint32 _l, _r;                                                        \
 158   const uint32 *_k = (k)->s;                                            \
 159                                                                         \
 160   _l = (a) + _k[0];                                                     \
 161   _r = (b) + _k[1];                                                     \
 162   _k += 2;                                                              \
 163                                                                         \
 164   EROUND(_l, _r, _k);                                                   \
 165   EROUND(_l, _r, _k);                                                   \
 166   EROUND(_l, _r, _k);                                                   \
 167   EROUND(_l, _r, _k);                                                   \
 168   EROUND(_l, _r, _k);                                                   \
 169   EROUND(_l, _r, _k);                                                   \
 170   EROUND(_l, _r, _k);                                                   \
 171   EROUND(_l, _r, _k);                                                   \
 172   EROUND(_l, _r, _k);                                                   \
 173   EROUND(_l, _r, _k);                                                   \
 174   EROUND(_l, _r, _k);                                                   \
 175   EROUND(_l, _r, _k);                                                   \
 176   (c) = _l;                                                             \
 177   (d) = _r;                                                             \
 178 } while (0)
 179
 180 #define DBLK(a, b, c, d, k) do {                                        \
 181   uint32 _l, _r;                                                        \
 182   const uint32 *_k = (k)->s + T;                                        \
 183                                                                         \
 184   _l = (a);                                                             \
 185   _r = (b);                                                             \
 186                                                                         \
 187   DROUND(_l, _r, _k);                                                   \
 188   DROUND(_l, _r, _k);                                                   \
 189   DROUND(_l, _r, _k);                                                   \
 190   DROUND(_l, _r, _k);                                                   \
 191   DROUND(_l, _r, _k);                                                   \
 192   DROUND(_l, _r, _k);                                                   \
 193   DROUND(_l, _r, _k);                                                   \
 194   DROUND(_l, _r, _k);                                                   \
 195   DROUND(_l, _r, _k);                                                   \
 196   DROUND(_l, _r, _k);                                                   \
 197   DROUND(_l, _r, _k);                                                   \
 198   DROUND(_l, _r, _k);                                                   \
 199                                                                         \
 200   _k -= 2;                                                              \
 201   (d) = _r - _k[1];                                                     \
 202   (c) = _l - _k[0];                                                     \
 203 } while (0)
 204
 205 /* --- @rc5_eblk@, @rc5_dblk@ --- *
 206  *
 207  * Arguments:   @const rc5_ctx *k@ = pointer to RC5 context block
 208  *              @const uint32 s[2]@ = pointer to source block
 209  *              @uint32 *d[2]@ = pointer to destination block
 210  *
 211  * Returns:     ---
 212  *
 213  * Use:         Low level block encryption and decryption.
 214  */
 215
 216 void rc5_eblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 217 {
 218   EBLK(s[0], s[1], d[0], d[1], k);
 219 }
 220
 221 void rc5_dblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 222 {
 223   DBLK(s[0], s[1], d[0], d[1], k);
 224 }
 225
 226 /* --- Test rig --- */
 227
 228 BLKC_TEST(RC5, rc5)
 229
 230 /*----- That's all, folks -------------------------------------------------*/