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| 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 */ | |
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