47 lines
883 B
C++
47 lines
883 B
C++
//
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// EQ2-Compatible RC4 Implementation
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//
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// It differs from standard RC4
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// - Fixed 64-bit key (int64_t), treated as 8 bytes in little-endian order
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// - Key scheduling cycles through the 8 key bytes using (i & 7)
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//
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#pragma once
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#include <cstdint>
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#include <cstddef>
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#include <cstring>
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class RC4 {
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public:
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void init(int64_t key) {
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for (int i = 0; i < 256; ++i)
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S[i] = static_cast<uint8_t>(i);
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uint8_t* keyBytes = reinterpret_cast<uint8_t*>(&key);
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uint8_t j = 0;
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for (int i = 0; i < 256; ++i) {
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j += S[i] + keyBytes[i & 7]; // cycle through 8 key bytes
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std::swap(S[i], S[j]);
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}
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i = 0;
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j = 0;
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}
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void process(uint8_t* data, size_t len) {
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for (size_t n = 0; n < len; ++n) {
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i += 1;
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j += S[i];
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std::swap(S[i], S[j]);
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uint8_t k = S[(S[i] + S[j]) & 0xFF];
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data[n] ^= k;
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}
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}
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private:
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uint8_t S[256];
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uint8_t i = 0;
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uint8_t j = 0;
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};
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