Let us start here, from square one. No, from Zero!

util/rc4.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <cstdint>
+
+namespace util {
+
+    class RC4 {
+    private:
+        uint8_t s_box[256];
+        size_t a = 0, b = 0;
+
+    public:
+
+        RC4(uint8_t *key, size_t key_size);
+
+        void crypt(uint8_t *data, size_t size);
+    };
+}