/* serpent.h
 *
 * The serpent block cipher.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001 Niels Möller
 *  
 * 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., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02111-1301, USA.
 */

/* Serpent is a 128-bit block cipher that accepts a key size of 256
 * bits, designed by Ross Anderson, Eli Biham, and Lars Knudsen. See
 * http://www.cl.cam.ac.uk/~rja14/serpent.html for details.
 */

#ifndef NETTLE_SERPENT_H_INCLUDED
#define NETTLE_SERPENT_H_INCLUDED

#include "nettle-types.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Name mangling */
#define serpent_set_key nettle_serpent_set_key
#define serpent_encrypt nettle_serpent_encrypt
#define serpent_decrypt nettle_serpent_decrypt

#define SERPENT_BLOCK_SIZE 16

/* Other key lengths are possible, but the design of Serpent makes
 * smaller key lengths quite pointless; they cheated with the AES
 * requirements, using a 256-bit key length exclusively and just
 * padding it out if the desired key length was less, so there really
 * is no advantage to using key lengths less than 256 bits. */
#define SERPENT_KEY_SIZE 32

/* Allow keys of size 128 <= bits <= 256 */

#define SERPENT_MIN_KEY_SIZE 16
#define SERPENT_MAX_KEY_SIZE 32

struct serpent_ctx
{
  uint32_t keys[33][4];  /* key schedule */
};

void
serpent_set_key(struct serpent_ctx *ctx,
                unsigned length, const uint8_t *key);

void
serpent_encrypt(const struct serpent_ctx *ctx,
                unsigned length, uint8_t *dst,
                const uint8_t *src);
void
serpent_decrypt(const struct serpent_ctx *ctx,
                unsigned length, uint8_t *dst,
                const uint8_t *src);

#ifdef __cplusplus
}
#endif

#endif /* NETTLE_SERPENT_H_INCLUDED */
