GnuPG

GnuPG is useful when a file needs an OpenPGP signature or encryption for a particular recipient. The command-line tool separates the data operation from management of the keys that identify the sender or recipient. Verify the intended recipient's key before encrypting and retain a deliberate recovery arrangement for your own keys. Its general data and key-management role is broader than an email plug-in. A successful signature check establishes a relationship to a key, which still needs a trusted identity context.