This document describes the key chain YANG data model. Key chains are commonly used for routing protocol authentication and other applications requiring symmetric keys. A key chain is a list containing one or more elements containing a Key ID@ key string@ send/accept lifetimes@ and the associated authentication or encryption algorithm. By properly overlapping the send and accept lifetimes of multiple key chain elements@ key strings and algorithms may be gracefully updated. By representing them in a YANG data model@ key distribution can be automated.