A quantum cryptographic protocol with detection of compromised server

This paper presents a server-based hybrid cryptographic protocol, using quantum and classical resources, to generate a key for authentication and optionally for encryption in a network. A novel feature of the protocol is that it can detect a compromised server. Additional advantages 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 attacks, and can be used with BB84 or other quantum key distribution protocols. Each resource shares a previously distributed secret key with the trusted server, and 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) .