salsa20.c

/* salsa20.c
 *
 * The Salsa20 stream cipher.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2012 Simon Josefsson
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/* Based on:
   salsa20-ref.c version 20051118
   D. J. Bernstein
   Public domain.
*/

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <string.h>

#include "salsa20.h"

#include "macros.h"
#include "memxor.h"

#ifdef WORDS_BIGENDIAN
#define LE_SWAP32(v)				\
  ((ROTL32(8,  v) & 0x00FF00FFUL) |		\
   (ROTL32(24, v) & 0xFF00FF00UL))
#else
#define LE_SWAP32(v) (v)
#endif

#define QROUND(x0, x1, x2, x3) do { \
  x1 ^= ROTL32(7, x0 + x3);	    \
  x2 ^= ROTL32(9, x1 + x0);	    \
  x3 ^= ROTL32(13, x2 + x1);	    \
  x0 ^= ROTL32(18, x3 + x2);	    \
  } while(0)

static void
salsa20_hash(uint32_t *output, const uint32_t *input)
{
  uint32_t x[_SALSA20_INPUT_LENGTH];
  int i;

  memcpy (x, input, sizeof (x));

  for (i = 20;i > 0;i -= 2) {
    QROUND(x[0], x[4], x[8], x[12]);
    QROUND(x[5], x[9], x[13], x[1]);
    QROUND(x[10], x[14], x[2], x[6]);