I had assumed it was SSL/TLS based on Wireshark. I've had to disable TLS via the jabber-config.xml to do lab testing/troubleshooting previously.
<UseSecureConnection>1</UseSecureConnection>
http://www.cisco.com/c/en/us/products/collateral/unified-communications/jabber-iphone/data_sheet_c78-690385.html
Cisco Jabber IM for iPhone lets you collaborate securely - even with colleagues outside your organization. The application uses the widely accepted Extensible Messaging and Presence Protocol (XMPP) Internet and presence IM standard that supports communication with networks outside your organization. You are ensured of communication privacy with user authentication and either 128-bit SSL or 256-bit Advanced Encryption Standard (AES) encryption.
http://www.cisco.com/c/en/us/products/unified-communications/jabber-extensible-communications-platform-xcp/jabber_faq.html
Q: How secure is Jabber XCP?
A: Jabber XCP is secure enough to support compliance regulations such as the Securities Exchange Commission (SEC) and Health Insurance Portability and Accountability (HIPAA). Jabber XCP security is used and trusted by the U.S. federal government.
It adheres to various accepted security industry standards including SSL, Transport Layer Security (TLS), HTTPS, and Simple Authentication and Security Layer (SASL). Jabber XCP is also flexible enough to be deployed in environments with highly customized security methods, means, and integration requirements.