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71 lines
2.9 KiB
71 lines
2.9 KiB
// Copyright (c) 2020, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <chrono>
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#include "crypto/crypto.h"
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namespace crypto
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{
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//! Generate poisson distributed values in discrete `D` time units.
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template<typename D>
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struct random_poisson_duration
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{
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using result_type = D; //!< std::chrono::duration time unit precision
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using rep = typename result_type::rep; //!< Type used to represent duration value
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//! \param average for generated durations
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explicit random_poisson_duration(result_type average)
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: dist(average.count() < 0 ? 0 : average.count())
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{}
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//! Generate a crypto-secure random duration
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result_type operator()()
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{
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crypto::random_device rand{};
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return result_type{dist(rand)};
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}
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private:
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std::poisson_distribution<rep> dist;
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};
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/* A custom duration is used for subsecond precision because of the
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variance. If 5000 milliseconds is given, 95% of the values fall between
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4859ms-5141ms in 1ms increments (not enough time variance). Providing 1/4
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seconds would yield 95% of the values between 3s-7.25s in 1/4s
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increments. */
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//! Generate random durations with 1 second precision
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using random_poisson_seconds = random_poisson_duration<std::chrono::seconds>;
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//! Generate random duration with 1/4 second precision
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using random_poisson_subseconds =
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random_poisson_duration<std::chrono::duration<std::chrono::milliseconds::rep, std::ratio<1, 4>>>;
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}
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