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   1 /* -*-c-*-
   2  *
   3  * $Id: xtea.c,v 1.3 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * The Extended Tiny Encryption Algorithm
   6  *
   7  * (c) 2000 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 <mLib/bits.h>
  33
  34 #include "blkc.h"
  35 #include "gcipher.h"
  36 #include "paranoia.h"
  37 #include "xtea.h"
  38
  39 /*----- Global variables --------------------------------------------------*/
  40
  41 const octet xtea_keysz[] = { KSZ_RANGE, XTEA_KEYSZ, 0, 16, 1 };
  42
  43 /*----- Main code ---------------------------------------------------------*/
  44
  45 /* --- @xtea_init@ --- *
  46  *
  47  * Arguments:   @xtea_ctx *k@ = pointer to key block
  48  *              @const void *buf@ = pointer to key buffer
  49  *              @size_t sz@ = size of key material
  50  *
  51  * Returns:     ---
  52  *
  53  * Use:         Initializes an XTEA key buffer.  The key buffer must be 16
  54  *              bytes long.
  55  */
  56
  57 void xtea_init(xtea_ctx *k, const void *buf, size_t sz)
  58 {
  59   octet kb[16];
  60   const octet *p;
  61
  62   KSZ_ASSERT(xtea, sz);
  63   if (sz >= sizeof(kb))
  64     p = buf;
  65   else {
  66     memcpy(kb, buf, sz);
  67     memset(kb + sz, 0, sizeof(kb) - sz);
  68     p = kb;
  69   }
  70
  71   k->k[0] = LOAD32(p +  0); k->k[1] = LOAD32(p +  4);
  72   k->k[2] = LOAD32(p +  8); k->k[3] = LOAD32(p + 12);
  73   k->r = 32;
  74
  75   if (p == kb)
  76     BURN(kb);
  77 }
  78
  79 /* --- @xtea_eblk@, @xtea_dblk@ --- *
  80  *
  81  * Arguments:   @const xtea_ctx *k@ = pointer to key block
  82  *              @const uint32 s[2]@ = pointer to source block
  83  *              @uint32 d[2]@ = pointer to xteatination block
  84  *
  85  * Returns:     ---
  86  *
  87  * Use:         Low-level block encryption and decryption.
  88  */
  89
  90 #define DELTA 0x9e3779b9
  91
  92 void xtea_eblk(const xtea_ctx *k, const uint32 *s, uint32 *d)
  93 {
  94   uint32 y = s[0], z = s[1];
  95   uint32 n = 0;
  96   unsigned i;
  97
  98   for (i = 0; i < k->r; i++) {
  99     y = U32(y + ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3])));
 100     n += DELTA;
 101     z = U32(z + ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3])));
 102   }
 103   d[0] = y; d[1] = z;
 104 }
 105
 106 void xtea_dblk(const xtea_ctx *k, const uint32 *s, uint32 *d)
 107 {
 108   uint32 y = s[0], z = s[1];
 109   uint32 n = DELTA * k->r;
 110   unsigned i;
 111
 112   for (i = 0; i < k->r; i++) {
 113     z = U32(z - ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3])));
 114     n -= DELTA;
 115     y = U32(y - ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3])));
 116   }
 117   d[0] = y; d[1] = z;
 118 }
 119
 120 BLKC_TEST(XTEA, xtea)
 121
 122 /*----- That's all, folks -------------------------------------------------*/