Is it possible to add End-to-End Encryption?

[Superlinna]

Another useful enhancement is to add End-to-End Encryption

Has been implemented in Android and in the unofficial tarek galal 's client yowsup/wazapp

More details here https://github.com/tgalal/yowsup#end-to-end-encryption

[CODeRUS]

It's not possible for Yappari as it using old WA12 protocol. Implementing encryption is possible only with WA15 protocol. And of course libcurve and libaxolotl are needed (but it will be available sooner or later)