git.distorted.org.uk Git - u/mdw/catacomb/blob - rijndael-base.c

   1 /* -*-c-*-
   2  *
   3  * $Id: rijndael-base.c,v 1.2 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Low-level stuff for all Rijndael block sizes
   6  *
   7  * (c) 2001 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 <stdio.h>
  34
  35 #include <mLib/bits.h>
  36
  37 #include "blkc.h"
  38 #include "gcipher.h"
  39 #include "rijndael.h"
  40 #include "rijndael-base.h"
  41 #include "rijndael-tab.h"
  42
  43 /*----- Global variables --------------------------------------------------*/
  44
  45 const octet rijndael_keysz[] = { KSZ_RANGE, RIJNDAEL_KEYSZ, 4, 32, 4 };
  46
  47 /*----- Constant tables ---------------------------------------------------*/
  48
  49 const octet rijndael_s[256] = RIJNDAEL_S;
  50 const octet rijndael_si[256] = RIJNDAEL_SI;
  51 const uint32 rijndael_t[4][256] = RIJNDAEL_T;
  52 const uint32 rijndael_ti[4][256] = RIJNDAEL_TI;
  53 const uint32 rijndael_u[4][256] = RIJNDAEL_U;
  54 const octet rijndael_rcon[] = RIJNDAEL_RCON;
  55
  56 /*----- Main code ---------------------------------------------------------*/
  57
  58 /* --- @rijndael_setup@ --- *
  59  *
  60  * Arguments:   @rijndael_ctx *k@ = pointer to context to initialize
  61  *              @unsigned nb@ = number of words in the block
  62  *              @const void *buf@ = pointer to buffer of key material
  63  *              @size_t sz@ = size of the key material
  64  *
  65  * Returns:     ---
  66  *
  67  * Use:         Low-level key-scheduling.
  68  */
  69
  70 void rijndael_setup(rijndael_ctx *k, unsigned nb, const void *buf, size_t sz)
  71 {
  72   unsigned nk, nr, nw;
  73   unsigned i, j, jj;
  74   const octet *p;
  75   uint32 ww;
  76
  77   /* --- Sort out the key size --- */
  78
  79   KSZ_ASSERT(rijndael, sz);
  80   nk = sz / 4;
  81
  82   /* --- Select the number of rounds --- */
  83
  84   nr = (nk > nb ? nk : nb) + 6;
  85   if (nr < 10)
  86     nr = 10;
  87   k->nr = nr;
  88
  89   /* --- Fetch the first key words out --- */
  90
  91   p = buf;
  92   for (i = 0; i < nk; i++) {
  93     k->w[i] = LOAD32_B(p);
  94     p += 4;
  95   }
  96
  97   /* --- Expand this material to fill the rest of the table --- */
  98
  99   nw = (nr + 1) * nb;
 100   ww = k->w[i - 1];
 101   p = RCON;
 102   for (; i < nw; i++) {
 103     uint32 w = k->w[i - nk];
 104     if (i % nk == 0) {
 105       ww = ROL32(ww, 8);
 106       w ^= SUB(S, ww, ww, ww, ww) ^ (*p++ << 24);
 107     } else if (nk > 6 && i % nk == 4)
 108       w ^= SUB(S, ww, ww, ww, ww);
 109     else
 110       w ^= ww;
 111     k->w[i] = ww = w;
 112   }
 113
 114   /* --- Make the decryption keys --- */
 115
 116   j = nw; i = 0;
 117
 118   j -= nb; jj = 0;
 119   for (; i < nb; i++)
 120     k->wi[i] = k->w[j + jj++];
 121
 122   for (; i < nw - nb; i += nb) {
 123     j -= nb;
 124     for (jj = 0; jj < nb; jj++) {
 125       uint32 w = k->w[j + jj];
 126       k->wi[i + jj] = MIX(U, w, w, w, w);
 127     }
 128   }
 129
 130   j -= nb; jj = 0;
 131   for (; i < nw; i++)
 132     k->wi[i] = k->w[j + jj++];
 133 }
 134
 135 /*----- That's all, folks -------------------------------------------------*/