A method and apparatus for verifying a request for service in a communication network. An authentication node generates a secret and transmits the secret to a node providing a service. The authentication node then receives a request for authentication from a requesting node, and once the requesting node is authenticated, the authorization node sends an identifier for the requesting node and a first token, which is derived using the secret and the identifier. A service providing node subsequently receives a request for service from the requesting node, the request including the identifier for the requesting node and the first token. The service providing node derives a second token using the identifier and the secret. If the first token and the second token match, then the service providing node allows the request, and if the first token and the second token do not match, then the request is refused.