Number of crackmes:
Number of solutions:
Simple decompilation using DnSpy.
As noted before, the entered key is used to decrypt the routine to display the message box. The pointer to the MessageboxA function is passed to the routine as a pointer. - Since the description says you should get a "success" message and the string is not available in the executable, it should be part of the encrypted routine. - The routine should return 0xc to not additionally show the "fail" messagebox. I searched for printable keys that would resolve to the routine either contain "success" or "ccus" (stack string) without any success. In my opinion this is just a guessing game making assumptions about the XORed code - hence a guessing game and not a proper crackme.