netwerk/srtp/src/crypto/math/gf2_8.c@6474c204b198 (annotated)
netwerk/srtp/src/crypto/math/gf2_8.c
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | /* |
| michael@0 | 2 | * gf2_8.c |
| michael@0 | 3 | * |
| michael@0 | 4 | * GF(256) finite field implementation, with the representation used |
| michael@0 | 5 | * in the AES cipher. |
| michael@0 | 6 | * |
| michael@0 | 7 | * David A. McGrew |
| michael@0 | 8 | * Cisco Systems, Inc. |
| michael@0 | 9 | */ |
| michael@0 | 10 | |
| michael@0 | 11 | /* |
| michael@0 | 12 | * |
| michael@0 | 13 | * Copyright (c) 2001-2006, Cisco Systems, Inc. |
| michael@0 | 14 | * All rights reserved. |
| michael@0 | 15 | * |
| michael@0 | 16 | * Redistribution and use in source and binary forms, with or without |
| michael@0 | 17 | * modification, are permitted provided that the following conditions |
| michael@0 | 18 | * are met: |
| michael@0 | 19 | * |
| michael@0 | 20 | * Redistributions of source code must retain the above copyright |
| michael@0 | 21 | * notice, this list of conditions and the following disclaimer. |
| michael@0 | 22 | * |
| michael@0 | 23 | * Redistributions in binary form must reproduce the above |
| michael@0 | 24 | * copyright notice, this list of conditions and the following |
| michael@0 | 25 | * disclaimer in the documentation and/or other materials provided |
| michael@0 | 26 | * with the distribution. |
| michael@0 | 27 | * |
| michael@0 | 28 | * Neither the name of the Cisco Systems, Inc. nor the names of its |
| michael@0 | 29 | * contributors may be used to endorse or promote products derived |
| michael@0 | 30 | * from this software without specific prior written permission. |
| michael@0 | 31 | * |
| michael@0 | 32 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| michael@0 | 33 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| michael@0 | 34 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| michael@0 | 35 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| michael@0 | 36 | * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| michael@0 | 37 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| michael@0 | 38 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| michael@0 | 39 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| michael@0 | 40 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| michael@0 | 41 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| michael@0 | 42 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
| michael@0 | 43 | * OF THE POSSIBILITY OF SUCH DAMAGE. |
| michael@0 | 44 | * |
| michael@0 | 45 | */ |
| michael@0 | 46 | |
| michael@0 | 47 | |
| michael@0 | 48 | #include "datatypes.h" |
| michael@0 | 49 | #include "gf2_8.h" |
| michael@0 | 50 | |
| michael@0 | 51 | /* gf2_8_shift() moved to gf2_8.h as an inline function */ |
| michael@0 | 52 | |
| michael@0 | 53 | gf2_8 |
| michael@0 | 54 | gf2_8_multiply(gf2_8 x, gf2_8 y) { |
| michael@0 | 55 | gf2_8 z = 0; |
| michael@0 | 56 | |
| michael@0 | 57 | if (y & 1) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 58 | if (y & 2) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 59 | if (y & 4) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 60 | if (y & 8) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 61 | if (y & 16) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 62 | if (y & 32) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 63 | if (y & 64) z ^= x; x = gf2_8_shift(x); |
| michael@0 | 64 | if (y & 128) z ^= x; |
| michael@0 | 65 | |
| michael@0 | 66 | return z; |
| michael@0 | 67 | } |
| michael@0 | 68 | |
| michael@0 | 69 | |
| michael@0 | 70 | /* this should use the euclidean algorithm */ |
| michael@0 | 71 | |
| michael@0 | 72 | gf2_8 |
| michael@0 | 73 | gf2_8_compute_inverse(gf2_8 x) { |
| michael@0 | 74 | unsigned int i; |
| michael@0 | 75 | |
| michael@0 | 76 | if (x == 0) return 0; /* zero is a special case */ |
| michael@0 | 77 | for (i=0; i < 256; i++) |
| michael@0 | 78 | if (gf2_8_multiply((gf2_8) i, x) == 1) |
| michael@0 | 79 | return (gf2_8) i; |
| michael@0 | 80 | |
| michael@0 | 81 | return 0; |
| michael@0 | 82 | } |
| michael@0 | 83 |
