release/src/router/nettle/salsa20-crypt.c

   1 /* salsa20-crypt.c
   2  *
   3  * The Salsa20 stream cipher.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2012 Simon Josefsson
   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., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 /* Based on:
  27    salsa20-ref.c version 20051118
  28    D. J. Bernstein
  29    Public domain.
  30 */
  31
  32 #if HAVE_CONFIG_H
  33 # include "config.h"
  34 #endif
  35
  36 #include <string.h>
  37
  38 #include "salsa20.h"
  39
  40 #include "macros.h"
  41 #include "memxor.h"
  42
  43 void
  44 salsa20_crypt(struct salsa20_ctx *ctx,
  45               unsigned length,
  46               uint8_t *c,
  47               const uint8_t *m)
  48 {
  49   if (!length)
  50     return;
  51
  52   for (;;)
  53     {
  54       uint32_t x[_SALSA20_INPUT_LENGTH];
  55
  56       _salsa20_core (x, ctx->input, 20);
  57
  58       ctx->input[9] += (++ctx->input[8] == 0);
  59
  60       /* stopping at 2^70 length per nonce is user's responsibility */
  61
  62       if (length <= SALSA20_BLOCK_SIZE)
  63         {
  64           memxor3 (c, m, (uint8_t *) x, length);
  65           return;
  66         }
  67       memxor3 (c, m, (uint8_t *) x, SALSA20_BLOCK_SIZE);
  68
  69       length -= SALSA20_BLOCK_SIZE;
  70       c += SALSA20_BLOCK_SIZE;
  71       m += SALSA20_BLOCK_SIZE;
  72   }
  73 }