Patent ID: 7363276

Claim:
A method of distributing information between a distributor and at least one receiver, comprising: receiving broadcasted and encrypted contents information with the receiver; periodically distributing first control information between the receiver and the distributor via a bi-directional communications channel at a first period, the first control information containing contract information for selecting some of a plurality of different channels, which is used to update contract information of second control information stored in the receiver, the contract information including a work key encrypted by a master key, and the second control information containing identification information unique to the receiver and required for the receiver to decrypt the contents information at a second period shorter than the first period, the master key and the work key being independent from the receiver and being required for the receiver to decrypt the contents information; sending back a receipt acknowledgement from the receiver via the bidirectional communications channel when the contract information of the second control information is updated; changing a transmission complete flag in response to the receipt acknowledgement, the transmission complete flag indicating if contract information is sent to the receiver; and controlling transmission of the first control information according to the transmission complete flag.