IP Phone Release 5.3 Bulletin

Cisco IP Phone firmware images now contain a
Cisco digital signature to provide authentication for
improved security. Once firmware version 5.3 is
loaded onto a phone, all subsequent firmware
versions will be checked for authenticity.

Firmware images prior to release 5.0 do not contain
a Cisco digital signature and therefore once version
5.3 is loaded onto a phone, all prior firmware
releases will be rejected. Only versions 5.0 or
greater will be accpected as it contains a Cisco 
digital signature.

For additional release 5.3 upgrade information
see the release notes.

SIP:
http://www.cisco.com/univercd/cc/td/doc/product/
voice/c_ipphon/english/ipp7960/addprot/
sip/relnote/phnrn53s.htm

MGCP:
http://www.cisco.com/univercd/cc/td/doc/product/
voice/c_ipphon/english/ipp7960/addprot/
mgcp/relnotes/phnrn53m.htm