Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
PhoneLeash: SMS/MMS forwarding - PhoneLeash: SMS/MMS forwarding app offers features that let you forward your desired text messages and multimedia messages to your email or your other mobile phone so that you can access them later.
OpenKeychain - OpenKeychain helps you communicate more privately and securely.
Easy Message - Easy Message app comes up with features to help users in effortlessly sending text messages to a phone number, which is not in the contact list.
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
Cellcrypt - Cellcrypt app provides features so you can enjoy secure conference calling, messaging, and sharing of documents.