It doesn't bode well for this app that its functionality depends so much on the file extension. It should depend on identifying actual PGP metadata: -----BEGIN PGP PUBLIC KEY BLOCK----- -----BEGIN PGP MESSAGE----- -----BEGIN PGP SIGNED MESSAGE----- That's what it should be looking for, regardless of the extension. I can point GPG (the reference implementation of OpenPGP) at any file with any name, and it will process it, as long as the block delineators are there. Just saying.