| 摘要 |
PROBLEM TO BE SOLVED: To provide a broadcast system that allows a user to easily view a program with a tentative contract. SOLUTION: A security module 22 in the contract information storage section 42 of which a program ID by which a viewer can view a program at tentative contract, a work key, number of days of an advanced tentative contract period, and an advanced tentative contract flag are stored in advance, is sold for viewers. A common individual information analysis section 41 extracts the current time included in common information supplied by a demultiplexer 31, adds the current time to the advanced tentative contract period stored in the contract information storage section 42 to calculate the validity limit of the work key. The common individual information analysis section 41 uses the work key to decode the common information and extracts a descramble key and gives it to a descrambler 32. The descrambler 32 uses the descramble key to descramble a video signal and an audio signal. |
