/mcpAuthorization specifies what an authenticated user, service, or application can do. You can implement multiple authentication and authorization methods in a single session. Image Authentication This process prevents tampering with the binary image, the firmware load, prior to loading it on the phone. Tampering with the image causes the phone to fail the authentication process and reject the image. Image authentication occurs through signed binary files that automatically install when you install Unified Communications Manager. Likewise, firmware updates that you download from the web also provide signed binary images. Device Authentication This process validates the identity of the communicating device and ensures that the entity is who it claims to be. Device authentication occurs between the Unified Communications Manager server and supported Cisco Unified IP Phones, SIP trunks, or JTAPI/TAPI/CTI applications (when supported). An authenticated connection occurs between these entities only when each entity accepts the certificate of the other entity. Mutual authentication describes this process of mutual certificate exchange. Device authentication relies on the creation of the CiscoCTL file (for authenticating Unified Communications Manager server node and applications), and the Certificate Authority Proxy Function (for authenticating phones and JTAPI/TAPI/CTI applications). A SIP user agent that connects via a SIP trunk authenticates to Unified Communications Manager if the CallManager trust store contains the SIP user agent certificate and if the SIP user agent contains the Unified Communications Manager certificate in its trust store. For information on updating the CallManager trust store, refer to the Administration Guide for Cisco Unified Communications Manager that supports this Unified Communications Manager release. Tip File Authentication This process validates digitally signed files that the phone downloads; for example, the configuration, ring list, locale, and CTL files. The phone validates the signature to verify that file tampering did not occur after the file creation. For a list of devices that are supported, see “Phone Model Support”. If you configure the cluster for mixed mode, the TFTP server signs static files, such as ring list, localized, default.cnf.xml, and ring list wav files, in.sgn format. The TFTP server signs files in <device name>.cnf.xml format every time that the TFTP server verifies that a data change occurred for the file. The TFTP server writes the signed files to disk if caching is disabled. If the TFTP server verifies that a saved file has changed, the TFTP server re-signs the file. The new file on the disk overwrites the saved file that gets deleted. Before the phone can download the new file, the administrator must restart affected devices in Unified Communications Manager. After the phone receives the files from the TFTP server, the phone verifies the integrity of the files by validating the signature on the file. For the phone to establish an authenticated connection, ensure that the following criteria are met: • A certificate must exist in the phone. Security Guide for Cisco Unified Communications Manager, Release 15 and SUs 15 An Introduction to Unified CM Security Image Authentication