First thanks for having programmed a software like this! It's all i needed!
The problem is for the second encryption method for secuxabber the one where the keys have to be exchanged per bluetooth... When the keys are exchanged then one receive an encrypted message when the other receive a unencrypted message! I've tried it on a galaxy note 2 and a samsung mini s3 and also on a virtual machines on android 4.4.
when ive tried with two account with the same phone its working...
So i hope you can do something to manage this !