If you brand it through ReFox, then ReFox will stop decompiling at a specified spot. W/o branding, ReFox will happily decompile your entire program. Other decompiling programs may ignore the scheme that ReFox uses. Can't think of any way to encrypt a program in a way to make it impossible to decompile. XORing the contents of the EXE file w/ some random data would indeed make it practically impossible to decompile the program -- with only one minor side-effect -- this also renders the EXE useless ;-).