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