81 lines
2.3 KiB
C++
81 lines
2.3 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2015-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#include "tea.hpp"
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#include <cstdint>
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#include <stdexcept>
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using cruft::crypto::block::TEA;
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///////////////////////////////////////////////////////////////////////////////
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static u32 constexpr MAGIC = 0x9E3779B9;
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static int constexpr ITERATIONS = 64;
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///////////////////////////////////////////////////////////////////////////////
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TEA::TEA (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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TEA::encrypt (cruft::view<word_t*> dst, cruft::view<word_t const*> src)
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{
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if (dst.size () != src.size ())
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throw std::invalid_argument ("mismatching encode/decode buffer sizes");
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if (src.size () % 2)
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throw std::invalid_argument ("TEA requires even data count");
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for (size_t i = 0, last = src.size (); i < last; i += 2) {
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word_t sum = 0;
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word_t v0 = src[i + 0];
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word_t v1 = src[i + 1];
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for (int j = 0; j < ITERATIONS; j += 2) {
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sum += MAGIC;
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v0 += ((v1 << 4) + m_key[0]) ^ (v1 + sum) ^ ((v1 >> 5) + m_key[1]);
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v1 += ((v0 << 4) + m_key[2]) ^ (v0 + sum) ^ ((v0 >> 5) + m_key[3]);
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}
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dst[i + 0] = v0;
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dst[i + 1] = v1;
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}
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}
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//-----------------------------------------------------------------------------
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void
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TEA::decrypt (cruft::view<word_t*> dst, cruft::view<word_t const*> src)
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{
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if (dst.size () != src.size ())
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throw std::invalid_argument ("mismatching encode/decode buffer sizes");
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if (src.size () % 2)
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throw std::invalid_argument ("TEA requires even data count");
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for (size_t i = 0, last = src.size (); i < last; i += 2) {
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word_t sum = MAGIC << 5;
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word_t v0 = src[i + 0];
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word_t v1 = src[i + 1];
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for (int j = 0; j < ITERATIONS; j += 2) {
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v1 -= ((v0 << 4) + m_key[2]) ^ (v0 + sum) ^ ((v0 >> 5) + m_key[3]);
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v0 -= ((v1 << 4) + m_key[0]) ^ (v1 + sum) ^ ((v1 >> 5) + m_key[1]);
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sum -= MAGIC;
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}
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dst[i + 0] = v0;
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dst[i + 1] = v1;
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}
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}
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