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

   1 /* -*-c-*-
   2  *
   3  * $Id: rc5.c,v 1.3 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * The RC5-32/12 block cipher
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <assert.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35
  36 #include <mLib/alloc.h>
  37 #include <mLib/bits.h>
  38
  39 #include "arena.h"
  40 #include "blkc.h"
  41 #include "gcipher.h"
  42 #include "rc5.h"
  43
  44 /*----- Global variables --------------------------------------------------*/
  45
  46 const octet rc5_keysz[] = { KSZ_RANGE, RC5_KEYSZ, 1, 255, 1 };
  47
  48 /*----- Internal magical constants ----------------------------------------*/
  49
  50 #define T ((RC5_ROUNDS + 1) * 2)
  51 #define P 0xb7e15163
  52 #define Q 0x9e3779b9
  53
  54 /*----- Main code ---------------------------------------------------------*/
  55
  56 /* --- @rc5_init@ --- *
  57  *
  58  * Arguments:   @rc5_ctx *k@ = pointer to a key block
  59  *              @const void *sbuf@ = pointer to key material
  60  *              @size_t sz@ = size of the key material
  61  *
  62  * Returns:     ---
  63  *
  64  * Use:         Initializes an RC5 key block.
  65  */
  66
  67 void rc5_init(rc5_ctx *k, const void *sbuf, size_t sz)
  68 {
  69   uint32 *l;
  70   size_t w;
  71
  72   /* --- Set up the @L@ table --- *
  73    *
  74    * This is slightly unfortunately defined.
  75    */
  76
  77   KSZ_ASSERT(rc5, sz);
  78
  79   {
  80     int i;
  81     const octet *p = sbuf;
  82
  83     /* --- Create the buffer --- */
  84
  85     w = (sz + 3) / 4;
  86     l = XS_ALLOC(w * sizeof(uint32));
  87
  88     /* --- Extract the key material --- */
  89
  90     for (i = 0; sz > 3; i++) {
  91       l[i] = LOAD32_L(p);
  92       p += 4;
  93       sz -= 4;
  94     }
  95
  96     /* --- Fix up the tail end --- */
  97
  98     if (sz) {
  99       uint32 x = U8(*p++);
 100       if (sz > 1) x |= (U8(*p++) <<  8);
 101       if (sz > 2) x |= (U8(*p++) << 16);
 102       l[i] = x;
 103     }
 104   }
 105
 106   /* --- Initialize the @S@ table --- */
 107
 108   {
 109     int i;
 110
 111     k->s[0] = P;
 112     for (i = 1; i < T; i++)
 113       k->s[i] = k->s[i - 1] + Q;
 114   }
 115
 116   /* --- Mix in the key --- */
 117
 118   {
 119     int m = 3 * (w > T ? w : T);
 120     int i, j, c;
 121     uint32 a, b;
 122
 123     for (c = i = j = a = b = 0; c < m; c++) {
 124       uint32 x;
 125
 126       x = k->s[i] + a + b;
 127       k->s[i] = a = ROL32(x, 3);
 128       i++; if (i >= T) i = 0;
 129
 130       x = l[j] + a + b;
 131       l[j] = b = ROL32(x, a + b);
 132       j++; if (j >= w) j = 0;
 133     }
 134   }
 135
 136   memset(l, 0, w * sizeof(uint32));
 137   XS_FREE(l);
 138 }
 139
 140 /* --- @EROUND@, @DROUND@ --- */
 141
 142 #define EROUND(x, y, k) do {                                            \
 143   uint32 _x;                                                            \
 144   _x = x ^ y; x = ROL32(_x, y) + k[0];                                  \
 145   _x = y ^ x; y = ROL32(_x, x) + k[1];                                  \
 146   k += 2;                                                               \
 147 } while (0)
 148
 149 #define DROUND(x, y, k) do {                                            \
 150   uint32 _x;                                                            \
 151   k -= 2;                                                               \
 152   _x = y - k[1]; y = ROR32(_x, x) ^ x;                                  \
 153   _x = x - k[0]; x = ROR32(_x, y) ^ y;                                  \
 154 } while (0)
 155
 156 /* --- @EBLK@, @DBLK@ --- */
 157
 158 #define EBLK(a, b, c, d, k) do {                                        \
 159   uint32 _l, _r;                                                        \
 160   const uint32 *_k = (k)->s;                                            \
 161                                                                         \
 162   _l = (a) + _k[0];                                                     \
 163   _r = (b) + _k[1];                                                     \
 164   _k += 2;                                                              \
 165                                                                         \
 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   EROUND(_l, _r, _k);                                                   \
 177   EROUND(_l, _r, _k);                                                   \
 178   (c) = _l;                                                             \
 179   (d) = _r;                                                             \
 180 } while (0)
 181
 182 #define DBLK(a, b, c, d, k) do {                                        \
 183   uint32 _l, _r;                                                        \
 184   const uint32 *_k = (k)->s + T;                                        \
 185                                                                         \
 186   _l = (a);                                                             \
 187   _r = (b);                                                             \
 188                                                                         \
 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   DROUND(_l, _r, _k);                                                   \
 200   DROUND(_l, _r, _k);                                                   \
 201                                                                         \
 202   _k -= 2;                                                              \
 203   (d) = _r - _k[1];                                                     \
 204   (c) = _l - _k[0];                                                     \
 205 } while (0)
 206
 207 /* --- @rc5_eblk@, @rc5_dblk@ --- *
 208  *
 209  * Arguments:   @const rc5_ctx *k@ = pointer to RC5 context block
 210  *              @const uint32 s[2]@ = pointer to source block
 211  *              @uint32 *d[2]@ = pointer to destination block
 212  *
 213  * Returns:     ---
 214  *
 215  * Use:         Low level block encryption and decryption.
 216  */
 217
 218 void rc5_eblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 219 {
 220   EBLK(s[0], s[1], d[0], d[1], k);
 221 }
 222
 223 void rc5_dblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 224 {
 225   DBLK(s[0], s[1], d[0], d[1], k);
 226 }
 227
 228 /* --- Test rig --- */
 229
 230 BLKC_TEST(RC5, rc5)
 231
 232 /*----- That's all, folks -------------------------------------------------*/