Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
OpenKeychain - OpenKeychain helps you communicate more privately and securely.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
GPG Suite - Use GPG Suite to encrypt, decrypt, sign and verify files or messages.
APG - Android Privacy Guard (APG) is a free and open source application for ...