surespot

The threat model also suggests that you verify key fingerprints manually if you are concerned about MITM.

Perhaps you can get a second impression-

details of threat model- https://www.surespot.me/documents/threat.html

details of how surespot works including crypto- https://www.surespot.me/documents/how_surespot_works.html

you can always review the code on GitHub- https://github.com/surespot/android

check out www.surespot.me for a great example of elliptic curve cryptography. surespot is a free and open source mobile messenger encrypting all messages end-to-end with 256 bit AES symmetric-key encryption using keys created with 521 bit ECDH shared secret derivation. surespot was built from the ground up to provide this exceptional security in an unobtrusive way, this is not a layer over something existing. surespot is like whatsapp but actually encrypted! group chat on the way.

surespot is a free and open source mobile messenger encrypting all messages end-to-end with 256 bit AES symmetric-key encryption using keys created with 521 bit ECDH shared secret derivation. www.surespot.me was built from the ground up to provide this exceptional security in an unobtrusive way, this is not a layer over something existing. surespot is like whatsapp but actually encrypted! group chat on the way.

We had our computers pretty well locked down but our mobile messages were still plain text so we wrote a whatsapp style mobile messenger over transparent end-to-end encryption. SURESPOT is free to use and open source, check out the source on GitHub, feedback is much appreciated. www.surespot.me