SMSSecure

Silence (formerly SMSSecure) is an SMS/MMS application that allows you to protect your privacy while communicating with friends. Using Silence, you can send SMS messages and share media or attachments with complete privacy.

Features: Easy. Silence works like any other SMS application. There's nothing to sign up for and no new service your friends need to join. Reliable. Silence communicates using encrypted SMS messages. No servers or internet connection required. Private. Silence uses the Signal encryption protocol to provide privacy for every message, every time. Safe. All messages are encrypted locally, so if your phone is lost or stolen, your messages are protected. Open Source. Silence is Free and Open Source, enabling anyone to verify its security by auditing the code.