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/**
* \file gcm.h
*
* \brief Galois/Counter mode for AES
*
* Copyright (C) 2006-2012, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef POLARSSL_GCM_H
#define POLARSSL_GCM_H
#include "aes.h"
#include <stdint.h>
#define GCM_ENCRYPT 1
#define GCM_DECRYPT 0
#define POLARSSL_ERR_GCM_AUTH_FAILED -0x0012 /**< Authenticated decryption failed. */
#define POLARSSL_ERR_GCM_BAD_INPUT -0x0014 /**< Bad input parameters to function. */
/**
* \brief GCM context structure
*/
typedef struct {
aes_context aes_ctx; /*!< AES context used */
uint64_t HL[16]; /*!< Precalculated HTable */
uint64_t HH[16]; /*!< Precalculated HTable */
}
gcm_context;
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief GCM initialization (encryption)
*
* \param ctx GCM context to be initialized
* \param key encryption key
* \param keysize must be 128, 192 or 256
*
* \return 0 if successful, or POLARSSL_ERR_AES_INVALID_KEY_LENGTH
*/
int gcm_init( gcm_context *ctx, const unsigned char *key, unsigned int keysize );
/**
* \brief GCM buffer encryption/decryption using AES
*
* \note On encryption, the output buffer can be the same as the input buffer.
* On decryption, the output buffer cannot be the same as input buffer.
* If buffers overlap, the output buffer must trail at least 8 bytes
* behind the input buffer.
*
* \param ctx GCM context
* \param mode GCM_ENCRYPT or GCM_DECRYPT
* \param length length of the input data
* \param iv initialization vector
* \param iv_len length of IV
* \param add additional data
* \param add_len length of additional data
* \param input buffer holding the input data
* \param output buffer for holding the output data
* \param tag_len length of the tag to generate
* \param tag buffer for holding the tag
*
* \return 0 if successful
*/
int gcm_crypt_and_tag( gcm_context *ctx,
int mode,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *input,
unsigned char *output,
size_t tag_len,
unsigned char *tag );
/**
* \brief GCM buffer authenticated decryption using AES
*
* \note On decryption, the output buffer cannot be the same as input buffer.
* If buffers overlap, the output buffer must trail at least 8 bytes
* behind the input buffer.
*
* \param ctx GCM context
* \param length length of the input data
* \param iv initialization vector
* \param iv_len length of IV
* \param add additional data
* \param add_len length of additional data
* \param tag buffer holding the tag
* \param tag_len length of the tag
* \param input buffer holding the input data
* \param output buffer for holding the output data
*
* \return 0 if successful and authenticated,
* POLARSSL_ERR_GCM_AUTH_FAILED if tag does not match
*/
int gcm_auth_decrypt( gcm_context *ctx,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *tag,
size_t tag_len,
const unsigned char *input,
unsigned char *output );
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if the test failed
*/
int gcm_self_test( int verbose );
#ifdef __cplusplus
}
#endif
#endif /* gcm.h */
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