git.distorted.org.uk Git - u/mdw/catacomb/blob - symm/xtea.c

   1 /* -*-c-*-
   2  *
   3  * The Extended Tiny Encryption Algorithm
   4  *
   5  * (c) 2000 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 <mLib/bits.h>
  31
  32 #include "blkc.h"
  33 #include "gcipher.h"
  34 #include "paranoia.h"
  35 #include "xtea.h"
  36
  37 /*----- Global variables --------------------------------------------------*/
  38
  39 const octet xtea_keysz[] = { KSZ_RANGE, XTEA_KEYSZ, 0, 16, 1 };
  40
  41 /*----- Main code ---------------------------------------------------------*/
  42
  43 /* --- @xtea_init@ --- *
  44  *
  45  * Arguments:   @xtea_ctx *k@ = pointer to key block
  46  *              @const void *buf@ = pointer to key buffer
  47  *              @size_t sz@ = size of key material
  48  *
  49  * Returns:     ---
  50  *
  51  * Use:         Initializes an XTEA key buffer.  The key buffer must be 16
  52  *              bytes long.
  53  */
  54
  55 void xtea_init(xtea_ctx *k, const void *buf, size_t sz)
  56 {
  57   octet kb[16];
  58   const octet *p;
  59
  60   KSZ_ASSERT(xtea, sz);
  61   if (sz >= sizeof(kb))
  62     p = buf;
  63   else {
  64     memcpy(kb, buf, sz);
  65     memset(kb + sz, 0, sizeof(kb) - sz);
  66     p = kb;
  67   }
  68
  69   k->k[0] = LOAD32(p +  0); k->k[1] = LOAD32(p +  4);
  70   k->k[2] = LOAD32(p +  8); k->k[3] = LOAD32(p + 12);
  71   k->r = 32;
  72
  73   if (p == kb)
  74     BURN(kb);
  75 }
  76
  77 /* --- @xtea_eblk@, @xtea_dblk@ --- *
  78  *
  79  * Arguments:   @const xtea_ctx *k@ = pointer to key block
  80  *              @const uint32 s[2]@ = pointer to source block
  81  *              @uint32 d[2]@ = pointer to xteatination block
  82  *
  83  * Returns:     ---
  84  *
  85  * Use:         Low-level block encryption and decryption.
  86  */
  87
  88 #define DELTA 0x9e3779b9
  89
  90 void xtea_eblk(const xtea_ctx *k, const uint32 *s, uint32 *d)
  91 {
  92   uint32 y = s[0], z = s[1];
  93   uint32 n = 0;
  94   unsigned i;
  95
  96   for (i = 0; i < k->r; i++) {
  97     y = U32(y + ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3])));
  98     n += DELTA;
  99     z = U32(z + ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3])));
 100   }
 101   d[0] = y; d[1] = z;
 102 }
 103
 104 void xtea_dblk(const xtea_ctx *k, const uint32 *s, uint32 *d)
 105 {
 106   uint32 y = s[0], z = s[1];
 107   uint32 n = DELTA * k->r;
 108   unsigned i;
 109
 110   for (i = 0; i < k->r; i++) {
 111     z = U32(z - ((((y << 4) ^ (y >> 5)) + y) ^ (n + k->k[(n >> 11) & 3])));
 112     n -= DELTA;
 113     y = U32(y - ((((z << 4) ^ (z >> 5)) + z) ^ (n + k->k[n & 3])));
 114   }
 115   d[0] = y; d[1] = z;
 116 }
 117
 118 BLKC_TEST(XTEA, xtea)
 119
 120 /*----- That's all, folks -------------------------------------------------*/