mirror of
https://github.com/biergaizi/codecrypt
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108 lines
2.4 KiB
C++
108 lines
2.4 KiB
C++
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/*
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* This file is part of Codecrypt.
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*
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* Copyright (C) 2013-2016 Mirek Kratochvil <exa.exa@gmail.com>
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*
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* Codecrypt is free software: you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or (at
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* your option) any later version.
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*
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* Codecrypt is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with Codecrypt. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _ccr_gf2m_h_
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#define _ccr_gf2m_h_
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#include <vector>
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#include "types.h"
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#include "sencode.h"
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/*
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* galois field of 2^m elements. Stored in an integer, for convenience.
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*/
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class gf2m
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{
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public:
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uint poly;
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uint n, m;
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bool create (uint m);
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std::vector<uint> log, antilog;
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inline uint add (uint a, uint b) {
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return a ^ b;
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}
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inline uint mult (uint a, uint b) {
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if (! (a && b)) return 0;
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return antilog[ (log[a] + log[b]) % (n - 1)];
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}
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inline uint exp (uint a, int k) {
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if (!a) return 0;
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return antilog[ (log[a] * k) % (n - 1)];
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}
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inline uint exp (int k) {
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//return x^k
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return exp (1 << 1, k);
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}
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inline uint inv (uint a) {
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if (!a) return 0;
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return antilog[ (n - 1 - log[a]) % (n - 1)];
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}
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inline uint inv_square (uint a) {
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if (!a) return 0;
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return antilog[ (2 * (n - 1 - log[a]))
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% (n - 1)];
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}
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inline uint div (uint a, uint b) {
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if (! (a && b)) return 0;
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return antilog[ (n - 1 - log[b] + log[a])
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% (n - 1)];
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}
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inline uint sq_root (uint a) {
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if (!a) return 0;
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uint t = log[a];
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if (t % 2) return antilog[ (t + n - 1) >> 1];
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else return antilog[t >> 1];
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}
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sencode* serialize();
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bool unserialize (sencode*);
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//optimized part of creating alternant check matrix
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template<class iter>
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inline void add_mults (uint base, uint step, iter begin, iter end) {
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if (begin == end || base == 0) return;
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*begin = add (*begin, base);
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++begin;
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if (begin == end || step == 0) return;
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uint lb = log[base], ls = log[step];
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for (; begin != end; ++begin) {
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lb = (lb + ls) % (n - 1);
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*begin = add (*begin, antilog[lb]);
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}
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}
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};
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#endif
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