92 lines
2 KiB
C++
92 lines
2 KiB
C++
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/*
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* This file is part of Codecrypt.
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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_permutation_h_
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#define _ccr_permutation_h_
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#include <vector>
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#include "types.h"
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#include "vector_item.h"
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#include "sencode.h"
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/*
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* permutation is stored as transposition table ordered from zero
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* e.g. (13)(2) is [2,1,0]
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*/
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class prng;
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class matrix;
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class permutation : public std::vector<uint>
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{
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protected:
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_ccr_declare_vector_item
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public:
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void compute_inversion (permutation&) const;
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void generate_random (uint n, prng&);
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void generate_identity (uint n) {
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resize (n);
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for (uint i = 0; i < n; ++i)
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item (i) = i;
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}
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//TODO permute_inv is easy, do it everywhere
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template<class A, class R> void permute (const A&a, R&r) const {
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r.resize (a.size() );
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for (uint i = 0; i < size(); ++i) r[item (i) ] = a[i];
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}
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void permute_rows (const matrix&, matrix&) const;
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//work-alike for dyadic permutations.
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template<class A, class R> static bool permute_dyadic
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(uint sig, const A&a, R&r) {
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//check if the thing has size 2^n
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uint s = a.size();
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while (s > 1) {
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if (s & 1) return false;
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s >>= 1;
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}
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if (sig >= a.size() ) return false;
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r.resize (a.size() );
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uint i, t, x;
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for (i = 0; i < a.size(); ++i) {
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r[sig] = a[i];
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//flip the correct bit in signature
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t = i + 1;
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x = 1;
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while (! (t & 1) ) {
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t >>= 1;
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x <<= 1;
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}
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sig ^= x;
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}
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return true;
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}
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sencode* serialize();
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bool unserialize (sencode*);
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};
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#endif
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