crypto/des3.c

   1 /* des3.h
   2  *
   3  * Triple DES cipher. Three key encrypt-decrypt-encrypt.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2001 Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  23  * MA 02111-1307, USA.
  24  */
  25
  26 #include "des.h"
  27
  28 /* It's possible to make some more general pipe construction, like the
  29  * lsh/src/cascade.c, but as in practice it's never used for anything
  30  * like triple DES, it's not worth the effort. */
  31
  32 /* On success, returns 1 and sets ctx->status to DES_OK (zero). On
  33  * error, returns 0 and sets ctx->status accordingly. */
  34 int
  35 des3_set_key(struct des3_ctx *ctx, const uint8_t *key)
  36 {
  37   unsigned i;
  38   for (i = 0; i<3; i++, key += DES_KEY_SIZE)
  39     if (!des_set_key(&ctx->des[i], key))
  40       {
  41         ctx->status = ctx->des[i].status;
  42         return 0;
  43       }
  44   ctx->status = DES_OK;
  45   return 1;
  46 }
  47
  48 void
  49 des3_encrypt(struct des3_ctx *ctx,
  50              unsigned length, uint8_t *dst,
  51              const uint8_t *src)
  52 {
  53   des_encrypt(&ctx->des[0],
  54               length, dst, src);
  55   des_decrypt(&ctx->des[1],
  56               length, dst, dst);
  57   des_encrypt(&ctx->des[2],
  58               length, dst, dst);
  59 }
  60
  61 void
  62 des3_decrypt(struct des3_ctx *ctx,
  63             unsigned length, uint8_t *dst,
  64             const uint8_t *src)
  65 {
  66   des_decrypt(&ctx->des[2],
  67               length, dst, src);
  68   des_encrypt(&ctx->des[1],
  69               length, dst, dst);
  70   des_decrypt(&ctx->des[0],
  71               length, dst, dst);
  72 }