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 | |
52 | typedef 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 | |
70 | gf2_8 |
71 | gf2_8_compute_inverse(gf2_8 x); |
72 | |
73 | void |
74 | test_gf2_8(void); |
75 | |
76 | gf2_8 |
77 | gf2_8_multiply(gf2_8 x, gf2_8 y); |
78 | |
79 | #endif /* GF2_8_H */ |
80 | |