Patent ID: 7792288

Claim:
A communication system using quantum cryptography comprising: subscriber stations connected to one or more quantum channels; one or more quantum-cryptographic device associated with the one or more quantum channels for generating a quantum key during use; and two or more interconnected switching stations that, during use, communicate via first public lines, using encryption agreed upon, without quantum-cryptographic key exchange; wherein, during use, the subscriber stations are connected to the switching stations via the one or more quantum channels that generate a respective temporary quantum key and are adapted to communicate via second public lines using the quantum key, and wherein the first public lines are distinct from the second public lines, and are a priori secure lines to transmit the generated quantum key from one switching station to another and to another subscriber station; wherein the subscriber stations involved in a given communication generate a separate key bit sequence with their associated switching station via the quantum channel after a request for a communication has been transmitted via a respective switching station during use; and wherein, during use, a switching station associated with a called subscriber station generates a third key bit sequence from the key bit sequences generated via the quantum channels and transmits this third key bit sequence to the called subscriber station which, using the key bit sequence known to it and generated by it together with the associated switching station, from the third key bit sequence generates the key bit sequence generated on the part of the calling subscriber station, which then finally is used as a mutual key for the communication between the subscriber stations.