105 lines
2.8 KiB
C++
105 lines
2.8 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#include "xxtea.hpp"
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#include <cstring>
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// test vectors: http://www.cix.co.uk/~klockstone/teavect.htm
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using util::crypto::XXTEA;
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//-----------------------------------------------------------------------------
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static const uint32_t MAGIC = 0x9E3779B9;
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static const unsigned ITERATIONS = 32; // each iteration performs two feistel rounds
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//-----------------------------------------------------------------------------
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static constexpr uint32_t mix (uint32_t Z,
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uint32_t Y,
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uint32_t S,
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size_t E,
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size_t P,
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const uint32_t *restrict K)
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{
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return ((Z >> 5 ^ Y << 2) + (Y >> 3 ^ Z << 4)) ^ ((S ^ Y) + (K[(P & 3) ^ E] ^ Z));
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}
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//-----------------------------------------------------------------------------
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XXTEA::XXTEA (key_t _key):
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m_key (_key)
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{ ; }
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//-----------------------------------------------------------------------------
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void
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XXTEA::encrypt (uint32_t *restrict data, size_t count)
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{
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if (count < 2)
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throw std::invalid_argument ("minimum blocksize is 64 bits");
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uint32_t sum = 0;
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uint32_t z = data[count - 1];
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uint32_t y, e, p;
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unsigned rounds = 6 + 52 / count;
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do {
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sum += MAGIC;
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e = (sum >> 2) & 3;
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for (p = 0; p < count - 1; p++) {
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y = data[p + 1];
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z = data[p] += mix (z, y, sum, e, p, m_key.data ());
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}
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y = data[0];
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z = data[count - 1] += mix (z, y, sum, e, p, m_key.data ());
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} while (--rounds);
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}
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//-----------------------------------------------------------------------------
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void
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XXTEA::decrypt (uint32_t *restrict data, size_t count)
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{
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if (count < 2)
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throw std::invalid_argument ("minimum blocksize is 64 bits");
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uint32_t y, z, sum;
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unsigned p, rounds, e;
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rounds = 6 + 52 / count;
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sum = rounds * MAGIC;
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y = data[0];
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do {
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e = (sum >> 2) & 3;
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for (p = count - 1; p > 0; p--) {
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z = data[p - 1];
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y = data[p ] -= mix (z, y, sum, e, p, m_key.data ());
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}
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z = data[count - 1];
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y = data[ 0] -= mix (z, y, sum, e, p, m_key.data ());
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sum -= MAGIC;
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} while (--rounds);
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}
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