camellia-set-decrypt-key.c 1.78 KB
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/* camellia-set-decrypt-key.c
 *
 * Inverse key setup for the camellia block cipher.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2010 Niels Mller
 *  
 * 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.
 */

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

#include "camellia.h"

#define SWAP(a, b) \
do { uint64_t t_swap = (a); (a) = (b); (b) = t_swap; } while(0)

void
camellia_invert_key(struct camellia_ctx *dst,
		    const struct camellia_ctx *src)
{
  unsigned nkeys = src->nkeys;
  unsigned i;
  if (dst == src)
    {
      SWAP(dst->keys[0], dst->keys[nkeys - 2]);
      for (i = 2; i < nkeys - 1 - i; i++)
	SWAP(dst->keys[i], dst->keys[nkeys - 1 - i]);
    }
  else
    {
      dst->nkeys = nkeys;
      dst->keys[0] = src->keys[nkeys - 2];
      for (i = 2; i < nkeys - 2; i++)
	dst->keys[i] = src->keys[nkeys - 1 - i];
      dst->keys[nkeys - 2] = src->keys[0];
    }
}

void
camellia_set_decrypt_key(struct camellia_ctx *ctx,
			 unsigned length, const uint8_t *key)
{
  camellia_set_encrypt_key(ctx, length, key);
  camellia_invert_key(ctx, ctx);
}