PURPOSE: To safely describute a key for cryptographic communication to the person concerned of communication, by constituting the titled system so that a cryptographic key peculiar to a user station is sent to a toll center, the toll center generates its cryptographic key, executes cryptographing by using it and distributes it to the user station, and the user station decoding it by using a decoding key of its own station.
CONSTITUTION: When user stations A, B have come to necessitate a cryptographic key for communication with regard to communication which is started newly or is executed already, said user stations A, B generate a cryptographing key and a decoding key for distributing the communication use cryptographic key, and send its distribution use cryptographing key to a toll center 1. The toll center 1 cryptographs the communication use cryptographic key allocated to communication of the user stations A, B, by using the distribution use cryptographing key and sends it to the user stations A, B. The user stations A, B obtain the communication use cryptographic key by decoding a signal from the toll center 1 by a distribution use decoding key. In such a way, no restriction is applied to both the communication use key and the distribution use key used for distributing the key, and also, according to such a system, it is unnecessary to manage concentrically these keys, and the safety is high.
NOHARA MITSUO
TAKAHATA FUMIO
