It's interesting and fun to implement this stuff; I totally agree. Emacs is amazing.

I worry people will get the wrong idea about security: The application used for decryption doesn't need to be the same as the one used for encryption, at least not for any serious attacker. That would be 'security through obscurity'. They need the encrypted text; they don't need Emacs.

More importantly, no matter who you are, that you implemented the encryption yourself (?) is a major flaw - unless you have a cryptography team that has matured the implementation over a decade or so. Nobody is good enough to do that by themself. As the saying goes, anyone can create an encryption routine that they can't break.