first commit

rc4.hpp

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+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+#include <algorithm>
+
+class RC4 {
+public:
+	void init(const uint8_t* key, size_t keyLen) {
+		for (int k = 0; k < 256; ++k)
+			S[k] = static_cast<uint8_t>(k);
+
+		uint8_t j = 0;
+		for (int k = 0; k < 256; ++k) {
+			j += S[k] + key[k % keyLen];
+			std::swap(S[k], S[j]);
+		}
+
+		i = 0;
+		j = 0;
+	}
+
+	void process(uint8_t* data, size_t len) {
+		for (size_t n = 0; n < len; ++n) {
+			i += 1;
+			j += S[i];
+			std::swap(S[i], S[j]);
+			uint8_t k = S[(S[i] + S[j]) & 0xFF];
+			data[n] ^= k;
+		}
+	}
+
+private:
+	uint8_t S[256];
+	uint8_t i = 0;
+	uint8_t j = 0;
+};

rc4_eq.hpp

@@ -0,0 +1,46 @@
+//
+// EQ2-Compatible RC4 Implementation
+//
+// It differs from standard RC4
+// - Fixed 64-bit key (int64_t), treated as 8 bytes in little-endian order
+// - Key scheduling cycles through the 8 key bytes using (i & 7)
+//
+
+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+#include <cstring>
+
+class RC4 {
+public:
+	void init(int64_t key) {
+		for (int i = 0; i < 256; ++i)
+			S[i] = static_cast<uint8_t>(i);
+
+		uint8_t* keyBytes = reinterpret_cast<uint8_t*>(&key);
+		uint8_t j = 0;
+		for (int i = 0; i < 256; ++i) {
+			j += S[i] + keyBytes[i & 7]; // cycle through 8 key bytes
+			std::swap(S[i], S[j]);
+		}
+
+		i = 0;
+		j = 0;
+	}
+
+	void process(uint8_t* data, size_t len) {
+		for (size_t n = 0; n < len; ++n) {
+			i += 1;
+			j += S[i];
+			std::swap(S[i], S[j]);
+			uint8_t k = S[(S[i] + S[j]) & 0xFF];
+			data[n] ^= k;
+		}
+	}
+
+private:
+	uint8_t S[256];
+	uint8_t i = 0;
+	uint8_t j = 0;
+};