/**
* Copyright (c) 2010 Werner Dittmann
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef SKEINAPI_H
#define SKEINAPI_H
/**
* @file skein_api.h
* @brief A Skein API and its functions.
* @{
*
* This API and the functions that implement this API simplify the usage
* of Skein. The design and the way to use the functions follow the openSSL
* design but at the same time take care of some Skein specific behaviour
* and possibilities.
*
* The functions enable applications to create a normal Skein hashes and
* message authentication codes (MAC).
*
* Using these functions is simple and straight forward:
*
* @code
*
* #include "skein_api.h"
*
* ...
* struct skein_ctx ctx; // a Skein hash or MAC context
*
* // prepare context, here for a Skein with a state size of 512 bits.
* skein_ctx_prepare(&ctx, SKEIN_512);
*
* // Initialize the context to set the requested hash length in bits
* // here request a output hash size of 31 bits (Skein supports variable
* // output sizes even very strange sizes)
* skein_init(&ctx, 31);
*
* // Now update Skein with any number of message bits. A function that
* // takes a number of bytes is also available.
* skein_update_bits(&ctx, message, msg_length);
*
* // Now get the result of the Skein hash. The output buffer must be
* // large enough to hold the request number of output bits. The application
* // may now extract the bits.
* skein_final(&ctx, result);
* ...
* @endcode
*
* An application may use @c skein_reset to reset a Skein context and use
* it for creation of another hash with the same Skein state size and output
* bit length. In this case the API implementation restores some internal
* internal state data and saves a full Skein initialization round.
*
* To create a MAC the application just uses @c skein_mac_init instead of
* @c skein_init. All other functions calls remain the same.
*
*/
#include <linux/types.h>
#include "skein_base.h"
/**
* Which Skein size to use
*/
enum skein_size {
SKEIN_256 = 256, /*!< Skein with 256 bit state */
SKEIN_512 = 512, /*!< Skein with 512 bit state */
SKEIN_1024 = 1024 /*!< Skein with 1024 bit state */
};
/**
* Context for Skein.
*
* 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, then adapt these
* structures as well.
*/
struct skein_ctx {
u64 skein_size;
u64 x_save[SKEIN_MAX_STATE_WORDS]; /* save area for state variables */
union {
struct skein_ctx_hdr h;
struct skein_256_ctx s256;
struct skein_512_ctx s512;
struct skein_1024_ctx s1024;
} m;
};
/**
* Prepare a Skein context.
*
* An application must call this function before it can use the Skein
* context. The functions clears memory and initializes size dependent
* variables.
*
* @param ctx
* Pointer to a Skein context.
* @param size
* Which Skein size to use.
* @return
* SKEIN_SUCCESS of SKEIN_FAIL
*/
int skein_ctx_prepare(struct skein_ctx *ctx, enum skein_size size);
/**
* Initialize a Skein context.
*
* Initializes the context with this data and saves the resulting Skein
* state variables for further use.
*
* @param ctx
* Pointer to a Skein context.
* @param hash_bit_len
* Number of MAC hash bits to compute
* @return
* SKEIN_SUCCESS of SKEIN_FAIL
* @see skein_reset
*/
int skein_init(struct skein_ctx *ctx, size_t hash_bit_len);
/**
* Resets a Skein context for further use.
*
* Restores the saved chaining variables to reset the Skein context.
* Thus applications can reuse the same setup to process several
* messages. This saves a complete Skein initialization cycle.
*
* @param ctx
* Pointer to a pre-initialized Skein MAC context
*/
void skein_reset(struct skein_ctx *ctx);
/**
* Initializes a Skein context for MAC usage.
*
* Initializes the context with this data and saves the resulting Skein
* state variables for further use.
*
* Applications call the normal Skein functions to update the MAC and
* get the final result.
*
* @param ctx
* Pointer to an empty or preinitialized Skein MAC context
* @param key
* Pointer to key bytes or NULL
* @param key_len
* Length of the key in bytes or zero
* @param hash_bit_len
* Number of MAC hash bits to compute
* @return
* SKEIN_SUCCESS of SKEIN_FAIL
*/
int skein_mac_init(struct skein_ctx *ctx, const u8 *key, size_t key_len,
size_t hash_bit_len);
/**
* Update Skein with the next part of the message.
*
* @param ctx
* Pointer to initialized Skein context
* @param msg
* Pointer to the message.
* @param msg_byte_cnt
* Length of the message in @b bytes
* @return
* Success or error code.
*/
int skein_update(struct skein_ctx *ctx, const u8 *msg,
size_t msg_byte_cnt);
/**
* Update the hash with a message bit string.
*
* Skein can handle data not only as bytes but also as bit strings of
* arbitrary length (up to its maximum design size).
*
* @param ctx
* Pointer to initialized Skein context
* @param msg
* Pointer to the message.
* @param msg_bit_cnt
* Length of the message in @b bits.
*/
int skein_update_bits(struct skein_ctx *ctx, const u8 *msg,
size_t msg_bit_cnt);
/**
* Finalize Skein and return the hash.
*
* Before an application can reuse a Skein setup the application must
* reset the Skein context.
*
* @param ctx
* Pointer to initialized Skein context
* @param hash
* Pointer to buffer that receives the hash. The buffer must be large
* enough to store @c hash_bit_len bits.
* @return
* Success or error code.
* @see skein_reset
*/
int skein_final(struct skein_ctx *ctx, u8 *hash);
/**
* @}
*/
#endif
