GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
SMS Plus - SMS Plus app offers features that let you forward text messages through internet connection as well as through other social media platforms.
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.
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.
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.