#include <Windows.h>

extern char *key;

#define START_ENCRYPTION(num) \
    static DWORD pointer##num; \
    static DWORD endpointer##num; \
    static bool encrypted##num; \
    if(encrypted##num) XOR(pointer##num, endpointer##num, key); \
    else \
    { \
SuperCoolLabel##num: \
        __asm { PUSH ESI } \
        __asm { MOV ESI, SuperCoolLabel##num } \
        __asm { MOV pointer##num, ESI } \
        __asm { POP ESI } \
    }


#define END_ENCRYPTION(num) \
    if(!encrypted##num) \
    { \
SuperCoolEndLabel##num: \
        __asm { PUSH ESI } \
        __asm { MOV ESI, SuperCoolEndLabel##num } \
        __asm { MOV endpointer##num, ESI } \
        __asm { POP ESI } \
    } \
    encrypted##num = true; \
    XOR(pointer##num, endpointer##num, key);


void XOR(DWORD start, DWORD end, char *theKey);

#define KEY_LENGTH 11
char key[KEY_LENGTH] = "thisisakey";

void XOR(DWORD start, DWORD end, char *theKey)
{
    for(DWORD i = start; i <= end; i++)
    {
        DWORD dwOldProtect;

        VirtualProtect((void*)i, 0x1, PAGE_READWRITE, &dwOldProtect);
        *(byte*)i ^= theKey[i % (KEY_LENGTH - 1)];
        VirtualProtect((void*)i, 0x1, dwOldProtect, &dwOldProtect);
    }
}