Cisco 8821 Manual page 109

Security profiles can be utilized to enable authenticated mode or encrypted mode, where signaling, media and configuration file
encryption is then enabled.
The Certificate Authority Proxy Function (CAPF) must be operational in order to utilize a Locally Signed Certificate (LSC)
with a security profile.
The Cisco Wireless IP Phone 8821 and 8821-EX have a Manufacturing Installed Certificate (MIC), which can be utilized with a
security profile as well.
The default device security profile is the model specific Standard SIP Non-Secure Profile, which does not utilize encryption.
Cisco Wireless IP Phone 8821 and 8821-EX Wireless LAN Deployment Guide
109