Limited receiving system capable of conducting partial audivision

Application Number: 00126310
Application Date: 2000.08.30
Publication Number: 1323142
Publication Date: 2001.11.21
Priority Information: 1999/12/21 JP 363297/99
International: H04N7/167
Applicant(s) Name: Mitsubishi Electric Corp.
Inventor(s) Name: Tsukahara Taisuke;Aita Yasutaka;Oka Susumi
Patent Agency Code: 72001
Patent Agent: jiang fuhou
Abstract A conditional access system includes an EMM (Entitlement Management Message) analyzer for retrieving partial viewing authorization information. When the partial viewing authorization information permits partial viewing, ECM (Entitlement Control Message) is decrypted using work keys, and scrambling keys are intermittently retrieved from the ECM. This can solve a problem of a conventional conditional access system in that an unauthorized user's receiver cannot display pictures at all because the receiver cannot retrieve scrambling keys, and hence the user cannot enjoy a program even to such a degree as to perceive its feeling as in analog broadcasting systems, and thus the user cannot decide as to whether to make contract or not with viewing the program to some extent, which prevents the provider of the program from offering effective invitation to the user.