gcmdata.c 1.98 KB
 Niels Möller committed Feb 06, 2011 1 ``````/* gcmdata.c `````` Niels Möller committed Apr 12, 2014 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 `````` Galois counter mode, specified by NIST, http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf Generation of fixed multiplication tables. Copyright (C) 2011 Niels Möller This file is part of GNU Nettle. GNU Nettle is free software: you can redistribute it and/or modify it under the terms of either: * the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. or * the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. or both in parallel, as here. GNU Nettle is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received copies of the GNU General Public License and the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/. */ `````` Niels Möller committed Feb 06, 2011 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 `````` #include #include #define GHASH_POLYNOMIAL 0xE1 /* When x is shifted out over the block edge, add multiples of the defining polynomial to eliminate each bit. */ static unsigned reduce(unsigned x) { unsigned p = GHASH_POLYNOMIAL << 1; unsigned y = 0; for (; x; x >>= 1, p <<= 1) if (x & 1) y ^= p; return y; } int `````` Niels Möller committed Mar 07, 2013 57 ``````main(int argc, char **argv) `````` Niels Möller committed Feb 06, 2011 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 ``````{ unsigned i; printf("4-bit table:\n"); for (i = 0; i<16; i++) { unsigned x; if (i && !(i%8)) printf("\n"); x = reduce(i << 4); printf("W(%02x,%02x),", x >> 8, x & 0xff); } printf("\n\n"); printf("8-bit table:\n"); for (i = 0; i<256; i++) { unsigned x; if (i && !(i%8)) printf("\n"); x = reduce(i); printf("W(%02x,%02x),", x >> 8, x & 0xff); } printf("\n"); return EXIT_SUCCESS; }``````