#ifndef _THREEFISHAPI_H_
#define _THREEFISHAPI_H_

/**
 * @file threefishApi.h
 * @brief A Threefish cipher API and its functions.
 * @{
 *
 * This API and the functions that implement this API simplify the usage
 * of the Threefish cipher. The design and the way to use the functions 
 * follow the openSSL design but at the same time take care of some Threefish
 * specific behaviour and possibilities.
 *
 * These are the low level functions that deal with Threefisch blocks only.
 * Implementations for cipher modes such as ECB, CFB, or CBC may use these 
 * functions.
 * 
@code
    // Threefish cipher context data
    ThreefishKey512_t keyCtx;

    // Initialize the context
    threefishSetKey(&keyCtx, Threefish512, key, tweak);

    // Encrypt
    threefishEncryptBlockBytes(&keyCtx, input, cipher);
@endcode
 */

#include <stdint.h>

#define KeyScheduleConst 0x1BD11BDAA9FC1A22L

#ifdef __cplusplus
extern "C"
{
#endif

    /**
     * Context for Threefish key and tweak words.
     * 
     * This structure was setup with some know-how of the internal
     * Skein structures, in particular ordering of header and size dependent
     * variables. If Skein implementation changes this, the adapt these
     * structures as well.
     */
    typedef struct ThreefishKey512 {
        uint64_t key[(512/64)+1]; /* + parity */
        uint64_t tweak[3];
    } ThreefishKey512_t;

    /**
     * Set Threefish key and tweak data.
     * 
     * This function sets the key and tweak data for the Threefish cipher of
     * the given size. The key data must have the same length (number of bits)
     * as the state size 
     *
     * @param keyCtx
     *     Pointer to a Threefish key structure.
     * @param keyData
     *     Pointer to the key words (word has 64 bits).
     * @param tweak
     *     Pointer to the two tweak words (word has 64 bits).
     */
    void threefishSetKey512(ThreefishKey512_t *keyCtx, uint64_t *keyData, uint64_t *tweak);

    void threefishEncrypt512(ThreefishKey512_t *keyCtx, uint64_t *input, uint64_t *output);

    void threefishDecrypt512(ThreefishKey512_t* keyCtx, uint64_t* input, uint64_t* output);

#ifdef __cplusplus
}
#endif

/**
 * @}
 */
#endif