Code:xor eax, eax xor ebx, ebx mov esi, *start adress of your code to crypt* mov edi, esi start: lodsb add bl, 25 ; changeable! add bh, 33 ; changeable!! add ah, 23 ; changeable!! add al, ah xor al, bl sub al, bh stosb cmp esi, *end adress of your code to crypt* jle start jmp OEP