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/* hmac.h - TinyCrypt interface to an HMAC implementation */
/*
* Copyright (C) 2015 by Intel Corporation, All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* hmac.h -- Interface to an HMAC implementation.
*
* Overview: HMAC is a message authentication code based on hash functions.
* TinyCrypt hard codes SHA-256 as the hash function. A message
* authentication code based on hash functions is also called a
* keyed cryptographic hash function since it performs a
* transformation specified by a key in an arbitrary length data
* set into a fixed length data set (also called tag).
*
* Security: The security of the HMAC depends on the length of the key and
* on the security of the hash function. Note that HMAC primitives
* are much less affected by collision attacks than their
* corresponding hash functions.
*
* Requires: SHA-256
*
* Usage: 1) call hmac_set_key to set the HMAC key.
*
* 2) call hmac_init to initialize a struct hash_state before
* processing the data.
*
* 3) call hmac_update to process the next input segment;
* hmac_update can be called as many times as needed to process
* all of the segments of the input; the order is important.
*
* 4) call hmac_final to out put the tag.
*/
#ifndef __HMAC_H__
#define __HMAC_H__
#include "sha256.h"
struct hmac_state_struct {
struct sha256_state_struct hash_state; /* the internal state required by h */
uint8_t key[2*SHA256_BLOCK_SIZE]; /* HMAC key schedule */
};
typedef struct hmac_state_struct *HmacState_t;
/*
* HMAC set key procedure.
*
* Effects: Configures ctx to use key and returns 1
*
* Exceptions: Returns 0 if
* ctx == NULL or
* key == NULL or
* key_size == 0.
*/
int32_t hmac_set_key (
HmacState_t ctx, /* IN/OUT -- the struct hmac_state_struct to initial */
const uint8_t *key, /* IN -- the HMAC key to configure */
uint32_t key_size);
/*
* HMAC init procedure.
*
* Effects: Initializes ctx to begin the next HMAC operation and returns 1
*
* Exceptions: Returns 0 if:
* ctx == NULL or
* key == NULL.
*/
int32_t hmac_init (
HmacState_t ctx); /* IN/OUT -- struct hmac_state_struct buffer to init */
/*
* HMAC update procedure.
*
* Assumes: state has been initialized by hmac_init
*
* Effects: Mixes data_length bytes addressed by data into state and
* returns 1
*
* Exceptions: Returns 0 if:
* ctx == NULL or
* key == NULL.
*
*/
int32_t hmac_update (
HmacState_t ctx, /* IN/OUT -- state of HMAC computation so far */
const void *data, /* IN -- data to incorporate into state */
uint32_t data_length); /* IN -- size of data in bytes */
/*
* HMAC final procedure.
*
* Assumes: The tag bufer is at least sizeof(hmac_tag_size(state)) bytes
* state has been initialized by hmac_init
*
* Effects: Writes the HMAC tag into the tag buffer and returns 1
*
* Exceptions: Returns 0 if:
* tag == NULL or
* ctx == NULL or
* key == NULL or
* taglen != SHA256_DIGEST_SIZE.
*
*/
int32_t hmac_final (
uint8_t *tag, /* IN/OUT -- buffer to receive computed HMAC tag */
uint32_t taglen, /* IN -- size of tag in bytes */
HmacState_t ctx); /* IN -- the HMAC state for computing tag */
#endif
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