85 lines
2.4 KiB
C++
85 lines
2.4 KiB
C++
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/*
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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 "xtea.hpp"
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using cruft::crypto::block::XTEA;
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///////////////////////////////////////////////////////////////////////////////
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static const uint32_t MAGIC = 0x9E3779B9;
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// each iteration performs two feistel rounds, for a total of 64
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static const unsigned ITERATIONS = 32;
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///////////////////////////////////////////////////////////////////////////////
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XTEA::XTEA (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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XTEA::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 ("XTEA requires even data count");
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auto last = data + count;
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while (data < last) {
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uint32_t sum = 0;
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uint32_t v0 = data[0];
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uint32_t v1 = data[1];
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for (unsigned i = 0; i < ITERATIONS; ++i) {
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v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + m_key[sum & 3]);
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sum += MAGIC;
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v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + m_key[(sum >> 11) & 3]);
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}
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*data++ = v0;
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*data++ = v1;
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}
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}
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//-----------------------------------------------------------------------------
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void
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XTEA::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 ("XTEA requires even data count");
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auto last = data + count;
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while (data < last) {
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uint32_t sum = ITERATIONS * MAGIC;
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uint32_t v0 = data[0];
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uint32_t v1 = data[1];
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for (unsigned i = 0; i < ITERATIONS; ++i) {
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v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + m_key[(sum >> 11) & 3]);
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sum -= MAGIC;
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v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + m_key[sum & 3]);
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}
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*data++ = v0;
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*data++ = v1;
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}
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}
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