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

   1 /* -*-c-*-
   2  *
   3  * The 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 "tea.h"
  36
  37 /*----- Global variables --------------------------------------------------*/
  38
  39 const octet tea_keysz[] = { KSZ_RANGE, TEA_KEYSZ, 0, 16, 1 };
  40
  41 /*----- Main code ---------------------------------------------------------*/
  42
  43 /* --- @tea_init@ --- *
  44  *
  45  * Arguments:   @tea_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 a TEA key buffer.  The key buffer must be 16
  52  *              bytes long.
  53  */
  54
  55 void tea_init(tea_ctx *k, const void *buf, size_t sz)
  56 {
  57   octet kb[16];
  58   const octet *p;
  59
  60   KSZ_ASSERT(tea, 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->ka = LOAD32(p +  0); k->kb = LOAD32(p +  4);
  70   k->kc = LOAD32(p +  8); k->kd = LOAD32(p + 12);
  71   k->r = 32;
  72
  73   if (p == kb)
  74     BURN(kb);
  75 }
  76
  77 /* --- @tea_eblk@, @tea_dblk@ --- *
  78  *
  79  * Arguments:   @const tea_ctx *k@ = pointer to key block
  80  *              @const uint32 s[2]@ = pointer to source block
  81  *              @uint32 d[2]@ = pointer to teatination block
  82  *
  83  * Returns:     ---
  84  *
  85  * Use:         Low-level block encryption and decryption.
  86  */
  87
  88 #define DELTA 0x9e3779b9
  89
  90 void tea_eblk(const tea_ctx *k, const uint32 *s, uint32 *d)
  91 {
  92   uint32 y = s[0], z = s[1];
  93   uint32 ka = k->ka, kb = k->kb, kc = k->kc, kd = k->kd;
  94   uint32 n = 0;
  95   unsigned i;
  96
  97   for (i = 0; i < k->r; i++) {
  98     n += DELTA;
  99     y = U32(y + (((z << 4) + ka) ^ (z + n) ^ ((z >> 5) + kb)));
 100     z = U32(z + (((y << 4) + kc) ^ (y + n) ^ ((y >> 5) + kd)));
 101   }
 102   d[0] = y; d[1] = z;
 103 }
 104
 105 void tea_dblk(const tea_ctx *k, const uint32 *s, uint32 *d)
 106 {
 107   uint32 y = s[0], z = s[1];
 108   uint32 ka = k->ka, kb = k->kb, kc = k->kc, kd = k->kd;
 109   uint32 n = DELTA * k->r;
 110   unsigned i;
 111
 112   for (i = 0; i < k->r; i++) {
 113     z = U32(z - (((y << 4) + kc) ^ (y + n) ^ ((y >> 5) + kd)));
 114     y = U32(y - (((z << 4) + ka) ^ (z + n) ^ ((z >> 5) + kb)));
 115     n -= DELTA;
 116   }
 117   d[0] = y; d[1] = z;
 118 }
 119
 120 BLKC_TEST(TEA, tea)
 121
 122 /*----- That's all, folks -------------------------------------------------*/