Hecker & Harriman
Crypt key system
 The present invention provides a concrete structure for applying a crypt key system to a television system, a database system or an electronic commercial transaction system or the like. This system consists of a broadcasting station, a database, a receiving apparatus, a data communication apparatus and a user terminal. As a crypt key system, a secret-key cryptosystem, a public-key cryptosystem, and a digital signature system are used. The keys used in the system are either encrypted or remain uncrypted to be supplied by broadcasting. The present invention is effective in preventing an unjustified use of the database system, managing copyrights, and in a pay-per-view system and a video-on-demand system. Further, the present invention is effective in realizing an electronic market which uses an electronic data information system. 
Mitsubishi Corporation
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Makoto
Saito