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/*
* gf2_8.h
*
* GF(256) implementation
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright (c) 2001-2006, Cisco Systems, Inc.
* 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 the Cisco Systems, Inc. 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 HOLDERS 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.
*
*/
#ifndef GF2_8_H
#define GF2_8_H
#include "datatypes.h" /* for uint8_t definition */
typedef uint8_t gf2_8;
#define gf2_8_field_polynomial 0x1B
/*
* gf2_8_shift(x) returns
*/
/*
* gf2_8_shift(z) returns the result of the GF(2^8) 'multiply by x'
* operation, using the field representation from AES; that is, the
* next gf2_8 value in the cyclic representation of that field. The
* value z should be an uint8_t.
*/
#define gf2_8_shift(z) (((z) & 128) ? \
(((z) << 1) ^ gf2_8_field_polynomial) : ((z) << 1))
gf2_8
gf2_8_compute_inverse(gf2_8 x);
void
test_gf2_8(void);
gf2_8
gf2_8_multiply(gf2_8 x, gf2_8 y);
#endif /* GF2_8_H */
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