cast6.h

/* Copyright (c) 2009, Markus Peloquin <markus@cs.wisc.edu>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED 'AS IS' AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
 * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef CAST6_H
#define CAST6_H

#include <features.h>

#ifdef __cplusplus
#	include <cstddef>
#	include <cstdint>

	/** Size of a CAST-256 block (bytes) */
	const size_t CAST6_BLOCK = 16;

	/** Minimum size of a CAST-256 key (bytes) */
	const size_t CAST6_KEY_MIN = 16;

	/** Maximum size of a CAST-256 key (bytes) */
	const size_t CAST6_KEY_MAX = 32;

	/** CAST-256 keys are all
	 * <code>CAST6_KEY_MIN + n * CAST6_KEY_STEP</code> bytes */
	const size_t CAST6_KEY_STEP = 4;
#else
#	include <stdbool.h>
#	include <stddef.h>
#	include <stdint.h>

#	define CAST6_BLOCK 16
#	define CAST6_KEY_MIN 16
#	define CAST6_KEY_MAX 32
#	define CAST6_KEY_STEP 4
#endif

struct cast6_ctx {
	uint32_t	Km[12][4];
	uint8_t		Kr[12][4];
};

#ifdef __cplusplus
extern "C" {
#endif

/** Initialize a CAST-256 context
 *
 * \param ctx		Uninitialized structure
 * \param key		Private key
 * \param sz		The size in bytes of the key. Valid sizes are
 *	16, 20, 24, 28, 32
 * \retval false	The key size is invalid
 */
bool	cast6_init(struct cast6_ctx *ctx, const uint8_t *key, uint8_t sz);

/** Encrypt a block of data
 *
 * It is fine if the two buffers are the same.
 *
 * \param[in] ctx		Context
 * \param[in] plaintext		Data to encrypt
 * \param[out] ciphertext	Encrypted data
 */
void	cast6_encrypt(const struct cast6_ctx *ctx,
	    const uint8_t plaintext[CAST6_BLOCK],
	    uint8_t ciphertext[CAST6_BLOCK]);

/** Decrypt a block of data
 *
 * It is fine if the two buffers are the same.
 *
 * \param[in] ctx		Context
 * \param[in] ciphertext	Data to decrypt
 * \param[out] plaintext	Decrypted data
 */
void	cast6_decrypt(const struct cast6_ctx *ctx,
	    const uint8_t ciphertext[CAST6_BLOCK],
	    uint8_t plaintext[CAST6_BLOCK]);

#ifdef __cplusplus
}
#endif

#endif