Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 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 */ |