US Patent 8041039 Secret communications system and channel control method

A secret communications system realizes point-to-multipoint or multipoint-to-multipoint connections of both quantum channels and classical channels. Multiple remote nodes are individually connected to a center node through optical fiber, and random-number strings K1 to KN are individually generated and shared between the respective remote nodes and the center node. Encrypted communication is performed between each remote node and the center node by using the corresponding one of the shared random-number strings K1 to KN as a cryptographic key. The center node is provided with a switch section for quantum channels and a switch section for classical channels. Switching control on each of these switch sections is performed independently of the other by a controller.