  This paper presents a hybrid cryptographic protocol, using quantum and
classical resources, for authentication and authorization in a network. One or
more trusted servers distribute streams of entangled photons to individual
resources that seek to communicate. It is assumed that each resource shares a
previously distributed secret key with the trusted server, and that resources
can communicate with the server using both classical and quantum channels.
Resources do not share secret keys with each other, so that the key
distribution problem for the network is reduced from O(n^2) to O(n). Some
advantages of the protocol are that it avoids the requirement for timestamps
used in classical protocols, guarantees that the trusted server cannot know the
authentication key, can provide resistance to multiple photon splitting attacks
and can be used with BB84 or other quantum key distribution protocols.
