120 lines
2.4 KiB
C++
120 lines
2.4 KiB
C++
#ifndef CHAOS_CIPHER_STREAM_ARC4_ARC4GEN_HPP
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#define CHAOS_CIPHER_STREAM_ARC4_ARC4GEN_HPP
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#include <cstdint>
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#include <vector>
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#include <utility>
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#include "Service/ChaosException.hpp"
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#include "Service/SeArray.hpp"
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namespace Chaos::Cipher::Stream::Arc4
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{
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class Arc4Gen
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{
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public:
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Arc4Gen()
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: IsInitialized_(false)
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{ }
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template<typename InputIt>
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Arc4Gen(InputIt keyBegin, InputIt keyEnd)
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{
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RekeyImpl(keyBegin, keyEnd);
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}
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template<typename InputIt>
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void Rekey(InputIt keyBegin, InputIt keyEnd)
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{
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RekeyImpl(keyBegin, keyEnd);
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}
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template<typename OutputIt>
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void Generate(OutputIt out, uint64_t bytesCount)
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{
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EnsureInitialized();
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for (uint64_t cnt = 0; cnt < bytesCount; ++cnt)
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{
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Step(1);
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*out++ = Lookup_[static_cast<uint8_t>(Lookup_[I_] + Lookup_[J_])];
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}
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}
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void Drop(uint64_t bytesCount)
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{
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EnsureInitialized();
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Step(bytesCount);
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}
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bool IsInitialized() const noexcept
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{
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return IsInitialized_;
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}
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private:
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Service::SeArray<uint8_t, 256> Lookup_;
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uint8_t I_;
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uint8_t J_;
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bool IsInitialized_;
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void EnsureInitialized() const
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{
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if (!IsInitialized_)
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{
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throw Service::ChaosException("Arc4Gen: not initialized");
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}
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}
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template<typename InputIt>
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void RekeyImpl(InputIt keyBegin, InputIt keyEnd)
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{
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IsInitialized_ = false;
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I_ = 0;
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J_ = 0;
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for (uint64_t idx = 0; idx < Lookup_.Size(); ++idx)
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{
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Lookup_[idx] = static_cast<uint8_t>(idx);
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}
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std::vector<uint8_t> key(keyBegin, keyEnd);
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if (key.size() < 5)
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{
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throw Service::ChaosException("Arc4Gen: key is too small");
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}
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uint8_t a = 0;
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uint8_t b = 0;
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for (uint64_t idx = 0; idx < Lookup_.Size(); ++idx)
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{
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a = static_cast<uint8_t>(idx);
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b = b + Lookup_[a] + key[a % key.size()];
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std::swap(Lookup_[a], Lookup_[b]);
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}
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IsInitialized_ = true;
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}
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void Step(uint64_t stepsCount)
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{
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for (uint64_t k = 0; k < stepsCount; ++k)
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{
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I_ = I_ + 1;
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J_ = J_ + Lookup_[I_];
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std::swap(Lookup_[I_], Lookup_[J_]);
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}
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}
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};
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} // namespace Chaos::Cipher::Stream::Arc4
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#endif // CHAOS_CIPHER_STREAM_ARC4_ARC4GEN_HPP
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