109 lines
2.3 KiB
C++
109 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 2018 Danny Robson <danny@nerdcruft.net>
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*/
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#include "speck.hpp"
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#include <cruft/util/bitwise.hpp>
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using cruft::crypto::block::speck;
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///////////////////////////////////////////////////////////////////////////////
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/// The round function for the encryption direction.
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///
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/// Mutates the x and y values.
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///
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/// \param x first data word
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/// \param y second data word
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/// \param k key word
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static void
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round_enc (u64 &x, u64 &y, u64 const &k)
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{
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x = cruft::rotater (x, 8);
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x += y;
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x ^= k;
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y = cruft::rotatel (y, 3);
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y ^= x;
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}
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///----------------------------------------------------------------------------
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/// The round function for the decryption direction
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///
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/// Mutates the x and y values.
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///
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/// \param x
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/// \param y
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/// \param k
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static void
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round_dec (u64 &x, u64 &y, u64 const &k)
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{
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y ^= x;
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y = cruft::rotater (y, 3);
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x ^= k;
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x -= y;
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x = cruft::rotatel (x, 8);
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}
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///////////////////////////////////////////////////////////////////////////////
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/// Initialise the key schedule
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speck::speck (std::array<u64,2> _key)
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{
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auto &x = _key[0];
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auto &y = _key[1];
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// Allocate a space to store the schedule as it's computed
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std::array<u64,32> schedule;
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schedule[0] = y;
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// Initialise the key to be indices 0..31
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std::iota (std::begin (m_key), std::end (m_key), 0);
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// 'encrypt' the key using the index schedule
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for (int i = 0; i < 31; ++i) {
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round_enc (x, y, m_key[i]);
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schedule[i + 1] = y;
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}
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// Copy the computed schedule back out
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m_key = schedule;
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}
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///////////////////////////////////////////////////////////////////////////////
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speck::block_t
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speck::encrypt (block_t plaintext) const
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{
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u64 &x = plaintext[0];
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u64 &y = plaintext[1];
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for (int i = 0; i < 32; i++)
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round_enc (x, y, m_key[i]);
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return { x, y };
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}
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//-----------------------------------------------------------------------------
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std::array<u64,2>
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speck::decrypt (block_t plaintext) const
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{
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u64 &x = plaintext[0];
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u64 &y = plaintext[1];
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for (int i = 0; i < 32; i++)
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round_dec (x, y, m_key[31 - i]);
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return { x, y };
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}
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