Signal Private Messenger is another instant messaging app aimed to guarantee the privacy of your communication. It claims that all of its chat messages are encrypted to provide you additional security.
You can stay anonymous in this app and communicate with others. Just enter a phone number (a thing that can easily be obtained anonymously in many countries) and start using it.
You can send messages to any of your contacts using Signal with end-to-end encryption. You can send any picture, document, video or audio file securely encrypted to group chats and single chats.