Signal

Privacy is possible, Signal makes it easy.

Using Signal, you can communicate instantly while avoiding SMS fees, create groups so that you can chat in real time with all your friends at once, and share media or attachments all with complete privacy. The server never has access to any of your communication and never stores any of your data.

★ Say Anything. Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.

★ Open Source. Signal is Free and Open Source, enabling anyone to verify its security by auditing the code. Signal is the only private messenger that uses open source peer-reviewed cryptographic protocols to keep your messages safe.

★ Be Yourself - Signal uses your existing phone number and address book. There are no separate logins, usernames, passwords, or PINs to manage or lose.

★ Group Chat. Signal allows you to create encrypted groups so you can have private conversations with all your friends at once. Not only are the messages encrypted, but the Signal server never has access to any group metadata such as the membership list, group title, or group icon.

★ Fast. The Signal protocol is designed to operate in the most constrained environment possible. Using Signal, messages are instantly delivered to friends.

★ Speak Freely - Make crystal-clear phone calls to people who live across town, or across the ocean, with no long-distance charges.

Signal is not currently compatible with tablets, but support for larger screens is on our roadmap and will be included in a future release!

For support, questions, or more information, please visit:
https://support.whispersystems.org

More details:
https://www.whispersystems.org/#encrypted_texts

Source code:
https://github.com/WhisperSystems/Signal-Android