[Mod edit - the below method/aia does not work]
I created the AIA file based on Chat app message style - #51 by TIMAI2.
Go to GitHub - iagolirapasssos/MITAppInventorchatServerClient: This repository contains the implementation of a secure chat application with server-client architecture, where messages are encrypted and decrypted using symmetric cryptography. Below is a detailed description of how it works, how to use it, security considerations, and future improvements.