From B1App you have 2 encryption options, both supported from B1XMPP chat server:
TLS – When you select TLS as encryption option you are using the same encryption used from any banks for the home banking access. More details about TLS protocol can be found here.
TLS+OTR – It does mean that you are adding to TLS, a further end-to-end encryption, specific for the instant messaging and related transfer files. You should use it to have the higher security level. More details about the OTR protocol are here.