libcruft-crypto/stream/salsa.cpp

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Copyright 2017-2018 Danny Robson <danny@nerdcruft.net>
 */


#include "./salsa.hpp"


///////////////////////////////////////////////////////////////////////////////
std::array<uint8_t,64>
cruft::crypto::stream::salsa20 (const std::array<uint8_t,64> bytes) noexcept
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
    auto x = *reinterpret_cast<const std::array<uint32_t,16>*> (&bytes);
    auto y = x;

    for (auto &t: x)
        t = util::ltoh (t);

    for (int i = 0; i < 10; ++i)
        x = salsa::doubleround (x);

    for (size_t i = 0; i < std::size (y); ++i)
        x[i] += y[i];

    for (auto &t: x)
        t = util::htol (t);

    return *reinterpret_cast<std::array<uint8_t,64>*> (&x);
#pragma GCC diagnostic pop
}