/mcpPurpose Command or Action For Cisco Unified IP Phones 7942 and 7962 (SIP only), Enter a 32-byte 0 as the key value for the symmetric key at the phone screen to disable encryption. Step 2 For information on how to perform these tasks, see the phone administration guide that supports your phone model. For Cisco Unified IP Phones (SIP only), delete the symmetric key at the phone screen to disable encryption. Step 3 Security Guide for Cisco Unified Communications Manager, Release 15 and SUs 111 Basic System Security Disable TFTP Encrypted Configuration Files