I really don't want to rely on security through obscurity... MS-DOS was written back when every programmer trusted everything that ran on the computer, security wasn't even an afterthought, and encryption was the sole domain of math nerds, conspiracy theorists, and the nerd equivalent of doomsday preppers because it was "too computationally expensive." Its sole saving grace in terms of security is that it doesn't support multitasking so malware can't run in the background, but you can just target whatever software it's running, instead.