OpenKeychain

Encryption is the best way to secure P2P communication and this app provides you this type of communication. Only senders and receivers can read the messages and there will be no interruption by any agency. Unique feature of OpenKeyChain is that it is open source and its information is available on git hub and everyone can examine every bit of it. Security experts has audit the OpenKeychain and they have found no major issue in the app and this is a very satisfactory report for this kind of app.