ltc_omac.c

加密认证联合模式的VS2005工程文件

/*
 ---------------------------------------------------------------------------
 Copyright (c) 1998-2006, Brian Gladman, Worcester, UK. All rights reserved.

 LICENSE TERMS

 The free distribution and use of this software in both source and binary
 form is allowed (with or without changes) provided that:

   1. distributions of this source code include the above copyright
      notice, this list of conditions and the following disclaimer;

   2. distributions in binary form include the above copyright
      notice, this list of conditions and the following disclaimer
      in the documentation and/or other associated materials;

   3. the copyright holder's name is not used to endorse products
      built using this software without specific written permission.

 ALTERNATIVELY, provided that this notice is retained in full, this product
 may be distributed under the terms of the GNU General Public License (GPL),
 in which case the provisions of the GPL apply INSTEAD OF those given above.

 DISCLAIMER

 This software is provided 'as is' with no explicit or implied warranties
 in respect of its properties, including, but not limited to, correctness
 and/or fitness for purpose.
 ---------------------------------------------------------------------------
 Issue Date: 13/06/2006

 This code has been derived from LibTomCrypt, the cryptographic library
 authored by Tom St Denis.  His contribution is hence acknowledged. This
 code has been developed to obtain two independent implementations of the
 combined AES encryption/authentication modes (CCM, GCM and EAX) in order
 to be able to check test vectors before their publication.
*/

#include <stdlib.h>
#include <string.h>

#include "ltc_omac.h"

int omac_init( const unsigned char key[], unsigned long key_len, omac_state omac[1] )
{
    int x, y, msb;

    if(aes_encrypt_key( key, key_len, omac->ctx ) != EXIT_SUCCESS)
        return EXIT_FAILURE;

    memset( omac->lu[0], 0, AES_BLOCK_SIZE );
    if(aes_encrypt( omac->lu[0], omac->lu[0], omac->ctx ) != EXIT_SUCCESS)
        return EXIT_FAILURE;

    for( x = 0; x < 2; x++ )
    {
        msb = omac->lu[x][0] >> 7;

        for( y = 0; y < (AES_BLOCK_SIZE - 1); y++ )
            omac->lu[x][y] = ( (omac->lu[x][y] << 1) | (omac->lu[x][y + 1] >> 7) ) & 0xff;

        omac->lu[x][AES_BLOCK_SIZE - 1] = ( (omac->lu[x][AES_BLOCK_SIZE - 1] << 1) ^ (msb ? 0x87 : 0x00) ) & 0xff;

        if( x == 0 )
            memcpy( omac->lu[1], omac->lu[0], sizeof(omac->lu[0]) );
    }

    omac->buflen = 0;
    memset( omac->prev, 0, sizeof(omac->prev) );
    memset( omac->block, 0, sizeof(omac->block) );
    return EXIT_SUCCESS;
}

int omac_process( const unsigned char in[], unsigned long in_len, omac_state omac[1] )
{
    unsigned long n, x;

    if( omac->buflen < 0 || omac->buflen > AES_BLOCK_SIZE )
        return EXIT_FAILURE;
    while( in_len != 0 )
    {
        if( omac->buflen == AES_BLOCK_SIZE )
        {
            for( x = 0; x < AES_BLOCK_SIZE; x++ )
                omac->block[x] ^= omac->prev[x];

            if(aes_encrypt( omac->block, omac->prev, omac->ctx ) != EXIT_SUCCESS)
                return EXIT_FAILURE;

            omac->buflen = 0;
        }

        n = ( in_len < AES_BLOCK_SIZE - omac->buflen ? in_len : AES_BLOCK_SIZE - omac->buflen );
        memcpy( omac->block + omac->buflen, in, n );
        omac->buflen += n;
        in_len -= n;
        in += n;
    }

    return EXIT_SUCCESS;
}

int omac_done( unsigned char out[], unsigned long *out_len, omac_state omac[1] )
{
    int mode;
    unsigned x;

    if( omac->buflen < 0 || omac->buflen > AES_BLOCK_SIZE )
        return EXIT_FAILURE;

    if( omac->buflen != AES_BLOCK_SIZE )
    {
        omac->block[omac->buflen++] = 0x80;

        while( omac->buflen < AES_BLOCK_SIZE )
            omac->block[omac->buflen++] = 0;
        mode = 1;
    }
    else
        mode = 0;

    for( x = 0; x < AES_BLOCK_SIZE; x++ )
        omac->block[x] ^= omac->prev[x] ^ omac->lu[mode][x];

    if(aes_encrypt( omac->block, omac->block, omac->ctx ) != EXIT_SUCCESS)
        return EXIT_FAILURE;

    for( x = 0; x < AES_BLOCK_SIZE && x < *out_len; x++ )
        out[x] = omac->block[x];
    *out_len = x;
    return EXIT_SUCCESS;
}

int omac_memory( const unsigned char key[], unsigned long key_len,
                 const unsigned char in[], unsigned long in_len,
                 unsigned char out[], unsigned long *out_len )
{
    int err;
    omac_state *omac;

    omac = malloc( sizeof(omac_state) );
    if( omac == NULL )
        return EXIT_FAILURE;

    if( (err = omac_init( key, key_len, omac )) != EXIT_SUCCESS )
        goto error;

    if( (err = omac_process( in, in_len, omac )) != EXIT_SUCCESS )
        goto error;

    if( (err = omac_done( out, out_len, omac )) != EXIT_SUCCESS )
        goto error;

    err = 0;
error:
    free( omac );
    return err;
}