1/*
2 * gf2_8.h
3 *
4 * GF(256) implementation
5 *
6 * David A. McGrew
7 * Cisco Systems, Inc.
8 */
9
10/*
11 *
12 * Copyright (c) 2001-2006, Cisco Systems, Inc.
13 * All rights reserved.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 *
19 * Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 *
22 * Redistributions in binary form must reproduce the above
23 * copyright notice, this list of conditions and the following
24 * disclaimer in the documentation and/or other materials provided
25 * with the distribution.
26 *
27 * Neither the name of the Cisco Systems, Inc. nor the names of its
28 * contributors may be used to endorse or promote products derived
29 * from this software without specific prior written permission.
30 *
31 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
34 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
35 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
36 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
37 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
38 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
40 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
41 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
42 * OF THE POSSIBILITY OF SUCH DAMAGE.
43 *
44 */
45
46
47#ifndef GF2_8_H
48#define GF2_8_H
49
50#include "datatypes.h" /* for uint8_t definition */
51
52typedef uint8_t gf2_8;
53
54#define gf2_8_field_polynomial 0x1B
55
56/*
57 * gf2_8_shift(x) returns
58 */
59
60/*
61 * gf2_8_shift(z) returns the result of the GF(2^8) 'multiply by x'
62 * operation, using the field representation from AES; that is, the
63 * next gf2_8 value in the cyclic representation of that field. The
64 * value z should be an uint8_t.
65 */
66
67#define gf2_8_shift(z) (((z) & 128) ? \
68 (((z) << 1) ^ gf2_8_field_polynomial) : ((z) << 1))
69
70gf2_8
71gf2_8_compute_inverse(gf2_8 x);
72
73void
74test_gf2_8(void);
75
76gf2_8
77gf2_8_multiply(gf2_8 x, gf2_8 y);
78
79#endif /* GF2_8_H */
80