XMPP supports additional security if the server and client support it, however some of the extension proposals (XEPs) are deferred or experimental. My hope that the Special Interest Group (SIG) for encryption pulls these together into new high-security client and high-security server profiles.

* https://xmpp.org/extensions/xep-0380.html - Explicit Message Encryption

* https://xmpp.org/extensions/xep-0429.html - Not a XEP really, but the formation of a SIG to explore a more robust end-to-end encryption support

* https://xmpp.org/extensions/xep-0420.html - Encrypting content specific to certain extensions

* https://xmpp.org/extensions/xep-0290.html - Digital signatures in XMPP