michael@0: /*
michael@0:  * gf2_8.h
michael@0:  *
michael@0:  * GF(256) implementation
michael@0:  *
michael@0:  * David A. McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  *	
michael@0:  * Copyright (c) 2001-2006, Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: 
michael@0: #ifndef GF2_8_H
michael@0: #define GF2_8_H
michael@0: 
michael@0: #include "datatypes.h"  /* for uint8_t definition */
michael@0: 
michael@0: typedef uint8_t gf2_8;
michael@0: 
michael@0: #define gf2_8_field_polynomial 0x1B
michael@0: 
michael@0: /*
michael@0:  * gf2_8_shift(x) returns 
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * gf2_8_shift(z) returns the result of the GF(2^8) 'multiply by x' 
michael@0:  * operation, using the field representation from AES; that is, the 
michael@0:  * next gf2_8 value in the cyclic representation of that field.  The 
michael@0:  * value z should be an uint8_t.
michael@0:  */
michael@0: 
michael@0: #define gf2_8_shift(z) (((z) & 128) ? \
michael@0:        (((z) << 1) ^ gf2_8_field_polynomial) : ((z) << 1))
michael@0: 
michael@0: gf2_8
michael@0: gf2_8_compute_inverse(gf2_8 x);
michael@0: 
michael@0: void
michael@0: test_gf2_8(void);
michael@0: 
michael@0: gf2_8
michael@0: gf2_8_multiply(gf2_8 x, gf2_8 y);
michael@0: 
michael@0: #endif /* GF2_8_H */