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2cf4253710
This implementation is optimized for a little code and data size, not for speed. IMO the code is more readable than in the reference implementation. The biggest advantage of ChaCha over other stream ciphers is the very little data usage with only 64 bytes of context, and its good encryption speed. Also part of this PR is pseudo-random number generator, that just returns the keystream of a randomly initialized ChaCha context.
65 lines
2.1 KiB
C
65 lines
2.1 KiB
C
/*
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* Copyright (C) 2015 René Kijewski <rene.kijewski@fu-berlin.de>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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/*
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* Please notice:
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* - I am not a cryptographer.
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* - You should not use this code to run a nuclear power plant without a proper review.
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*/
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#include "crypto/chacha.h"
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#include "mutex.h"
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#include <string.h>
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static chacha_ctx _chacha_prng_ctx = {
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.state = { RIOT_CHACHA_PRNG_DEFAULT },
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.rounds = 8,
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};
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static uint32_t _chacha_prng_data[64];
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static signed _chacha_prng_pos = 0;
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static mutex_t _chacha_prng_mutex = MUTEX_INIT;
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void chacha_prng_seed(const void *data, size_t bytes)
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{
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mutex_lock(&_chacha_prng_mutex);
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memcpy(_chacha_prng_ctx.state, data, bytes);
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_chacha_prng_pos = 0;
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mutex_unlock(&_chacha_prng_mutex);
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}
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uint32_t chacha_prng_next(void)
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{
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mutex_lock(&_chacha_prng_mutex);
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if (--_chacha_prng_pos < 0) {
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_chacha_prng_pos = 15;
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chacha_keystream_bytes(&_chacha_prng_ctx, _chacha_prng_data);
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}
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uint32_t result = _chacha_prng_data[_chacha_prng_pos];
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mutex_unlock(&_chacha_prng_mutex);
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return result;
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}
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