Mirek Kratochvil
8c185c51ad
codecrypt is usually invoked only with one prepare() and decrypt(), so this basically saves several megs of memory and cuts needed computation time in half.
105 lines
2.6 KiB
C++
105 lines
2.6 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_mce_qd_h_
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#define _ccr_mce_qd_h_
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#include <vector>
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#include "bvector.h"
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#include "gf2m.h"
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#include "matrix.h"
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#include "permutation.h"
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#include "polynomial.h"
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#include "prng.h"
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#include "sencode.h"
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#include "types.h"
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/*
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* compact Quasi-dyadic McEliece
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* according to Misoczki, Barreto, Compact McEliece Keys from Goppa Codes.
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*
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* Good security, extremely good speed with extremely reduced key size.
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* Recommended for encryption, but NEEDS some plaintext conversion -- either
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* Fujisaki-Okamoto or Kobara-Imai are known to work good. Without the
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* conversion, the encryption itself is extremely weak.
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*/
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namespace mce_qd
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{
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class privkey
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{
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public:
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std::vector<uint> essence;
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gf2m fld; //we fix q=2^fld.m=fld.n, n=q/2
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uint T; //the QD's t parameter is 2^T.
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permutation block_perm; //order of blocks
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std::vector<uint> block_perms; //dyadic permutations of blocks
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permutation hperm; //block permutation of H block used to get G
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//derivable stuff
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//pre-permuted positions of support rows and support content
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std::vector<uint> support_pos, permuted_support;
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//generating polynomial
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polynomial g;
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int decrypt (const bvector&, bvector&);
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int decrypt (const bvector&, bvector&, bvector&);
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int prepare();
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uint cipher_size() {
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return (1 << T) * hperm.size();
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}
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uint plain_size() {
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return (1 << T) * (hperm.size() - fld.m);
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}
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uint error_count() {
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return 1 << T;
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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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class pubkey
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{
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public:
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uint T;
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matrix qd_sigs;
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int encrypt (const bvector&, bvector&, prng&);
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int encrypt (const bvector&, bvector&, const bvector&);
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uint cipher_size() {
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return plain_size() + qd_sigs[0].size();
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}
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uint plain_size() {
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return (1 << T) * qd_sigs.size();
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}
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uint error_count() {
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return 1 << T;
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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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int generate (pubkey&, privkey&, prng&, uint m, uint T, uint b, uint bd);
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}
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#endif
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