Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
OpenKeychain - OpenKeychain helps you communicate more privately and securely.
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.
APG - Android Privacy Guard (APG) is a free and open source application for ...