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

   1 /* -*-c-*-
   2  *
   3  * $Id: rc5.c,v 1.1 1999/09/03 08:41:12 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: rc5.c,v $
  33  * Revision 1.1  1999/09/03 08:41:12  mdw
  34  * Initial import.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include <assert.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43
  44 #include <mLib/alloc.h>
  45 #include <mLib/bits.h>
  46
  47 #include "blkc.h"
  48 #include "rc5.h"
  49
  50 /*----- Internal magical constants ----------------------------------------*/
  51
  52 #define RC5_ROUNDS 12
  53
  54 #define T ((RC5_ROUNDS + 1) * 2)
  55 #define P 0xb7e15163
  56 #define Q 0x9e3779b9
  57
  58 /*----- Main code ---------------------------------------------------------*/
  59
  60 /* --- @rc5_init@ --- *
  61  *
  62  * Arguments:   @rc5_ctx *k@ = pointer to a key block
  63  *              @const void *sbuf@ = pointer to key material
  64  *              @size_t sz@ = size of the key material
  65  *
  66  * Returns:     ---
  67  *
  68  * Use:         Initializes an RC5 key block.
  69  */
  70
  71 void rc5_init(rc5_ctx *k, const void *sbuf, size_t sz)
  72 {
  73   uint32 *l;
  74   size_t w;
  75
  76   /* --- Set up the @L@ table --- *
  77    *
  78    * This is slightly unfortunately defined.
  79    */
  80
  81   assert(((void)"RC5 does not support zero-length keys", sz != 0));
  82
  83   {
  84     int i;
  85     const octet *p = sbuf;
  86
  87     /* --- Create the buffer --- */
  88
  89     w = (sz + 3) / 4;
  90     l = xmalloc(w * sizeof(uint32));
  91
  92     /* --- Extract the key material --- */
  93
  94     for (i = 0; sz > 3; i++) {
  95       l[i] = LOAD32_L(p);
  96       p += 4;
  97       sz -= 4;
  98     }
  99
 100     /* --- Fix up the tail end --- */
 101
 102     if (sz) {
 103       uint32 x = U8(*p++);
 104       if (sz > 1) x |= (U8(*p++) <<  8);
 105       if (sz > 2) x |= (U8(*p++) << 16);
 106       l[i] = x;
 107     }
 108   }
 109
 110   /* --- Initialize the @S@ table --- */
 111
 112   {
 113     int i;
 114
 115     k->s[0] = P;
 116     for (i = 1; i < T; i++)
 117       k->s[i] = k->s[i - 1] + Q;
 118   }
 119
 120   /* --- Mix in the key --- */
 121
 122   {
 123     int m = 3 * (w > T ? w : T);
 124     int i, j, c;
 125     uint32 a, b;
 126
 127     for (c = i = j = a = b = 0; c < m; c++) {
 128       uint32 x;
 129
 130       x = k->s[i] + a + b;
 131       k->s[i] = a = ROL32(x, 3);
 132       i++; if (i >= T) i = 0;
 133
 134       x = l[j] + a + b;
 135       l[j] = b = ROL32(x, a + b);
 136       j++; if (j >= w) j = 0;
 137     }
 138   }
 139
 140   free(l);
 141 }
 142
 143 /* --- @EROUND@, @DROUND@ --- */
 144
 145 #define EROUND(x, y, k) do {                                            \
 146   uint32 _x;                                                            \
 147   _x = x ^ y; x = ROL32(_x, y) + k[0];                                  \
 148   _x = y ^ x; y = ROL32(_x, x) + k[1];                                  \
 149   k += 2;                                                               \
 150 } while (0)
 151
 152 #define DROUND(x, y, k) do {                                            \
 153   uint32 _x;                                                            \
 154   k -= 2;                                                               \
 155   _x = y - k[1]; y = ROR32(_x, x) ^ x;                                  \
 156   _x = x - k[0]; x = ROR32(_x, y) ^ y;                                  \
 157 } while (0)
 158
 159 /* --- @EBLK@, @DBLK@ --- */
 160
 161 #define EBLK(a, b, c, d, k) do {                                        \
 162   uint32 _l, _r;                                                        \
 163   const uint32 *_k = (k)->s;                                            \
 164                                                                         \
 165   _l = (a) + _k[0];                                                     \
 166   _r = (b) + _k[1];                                                     \
 167   _k += 2;                                                              \
 168                                                                         \
 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   EROUND(_l, _r, _k);                                                   \
 179   EROUND(_l, _r, _k);                                                   \
 180   EROUND(_l, _r, _k);                                                   \
 181   (c) = _l;                                                             \
 182   (d) = _r;                                                             \
 183 } while (0)
 184
 185 #define DBLK(a, b, c, d, k) do {                                        \
 186   uint32 _l, _r;                                                        \
 187   const uint32 *_k = (k)->s + T;                                        \
 188                                                                         \
 189   _l = (a);                                                             \
 190   _r = (b);                                                             \
 191                                                                         \
 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   DROUND(_l, _r, _k);                                                   \
 202   DROUND(_l, _r, _k);                                                   \
 203   DROUND(_l, _r, _k);                                                   \
 204                                                                         \
 205   _k -= 2;                                                              \
 206   (d) = _r - _k[1];                                                     \
 207   (c) = _l - _k[0];                                                     \
 208 } while (0)
 209
 210 /* --- @rc5_eblk@, @rc5_dblk@ --- *
 211  *
 212  * Arguments:   @const rc5_ctx *k@ = pointer to RC5 context block
 213  *              @const uint32 s[2]@ = pointer to source block
 214  *              @uint32 *d[2]@ = pointer to destination block
 215  *
 216  * Returns:     ---
 217  *
 218  * Use:         Low level block encryption and decryption.
 219  */
 220
 221 void rc5_eblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 222 {
 223   EBLK(s[0], s[1], d[0], d[1], k);
 224 }
 225
 226 void rc5_dblk(const rc5_ctx *k, const uint32 *s, uint32 *d)
 227 {
 228   DBLK(s[0], s[1], d[0], d[1], k);
 229 }
 230
 231 /* --- Test rig --- */
 232
 233 BLKC_TEST(RC5, rc5)
 234
 235 /*----- That's all, folks -------------------------------------------------*/