ZRTP

ZRTP stands for 'Z Real-time Protocol'. It is a way to send messages instantly and securely. ZRTP works by scrambling (encrypting) your messages so that only the person you are messaging can read them. The encryption also makes sure that no one else can listen in on your conversation. All you need to do to use ZRTP is make sure both you and your friend have the same type of messaging app installed.