A method and apparatus for authenticating a first node's identity in a communication network. An authentication node receives from a second node an authentication request. The authentication request includes a first certificate that has previously been presented to the second node by a node purporting to be the first node. The authentication node retrieves a second certificate belonging to the first node from the first node, and compares the first certificate with the second certificate. If the certificates match, then the first node's identity can be authenticated but if the certificates do not match, then the first node's identity cannot be authenticated. The results of the comparison are then sent to the second node.