End-to-End-Messenger with Sealed Sender

This Messenger is an implementation of Sealed-SMS based on the Signal Protocols linked below.

e2e Messenger: https://www.signal.org/docs/specifications/doubleratchet/

Sealed Sender: https://signal.org/blog/sealed-sender/

x3dh Key Exchange: https://signal.org/docs/specifications/x3dh/