Broadcast receiving method and apparatus and information distributing method and apparatus

A broadcast receiving method comprising:

• storing first control information in a storage device of a receiver, the first control information containing identification information unique to the receiver and contract information for selecting some of a plurality of different channels, the first control information required for the receiver to select broadcasted and encrypted contents information, the contract information including a work key encrypted by a master key;
• receiving second control information with the receiver via a bi-directional communications channel, the second control information containing contract information for updating;
• periodically updating at a first period the contract information of the first control information in the storage device to the contract information of the second control information;
• sending back a receipt acknowledgement from the receiver via the bi-directional communications channel when the contract information of the first control information is updated;
• periodically receiving encrypted key information which is independent of the receiver and broadcasted to decrypt the contents information at a second period shorter than the first period, the encrypted key information being encrypted by the work key;
• decrypting the encrypted key information to obtain decrypted key information;
• storing the decrypted key information in the storage device;
• determining whether the stored decrypted key information is valid based on the contract information;
• and
• decrypting the contents information based on the decrypted key information that has been determined to be valid and updated contract information of the first control information.

A broadcast receiving apparatus communicating with a first distributor which performs bi-directional communications, and a second distributor which performs a broadcast transmission, comprising:

• a storage device configured to store first control information containing identification information and contract information, the first control information being required to select encrypted contents information broadcasted by the second distributor, and the contract information including a work key encrypted by a master key;
• a first receiver configured to receive second control information distributed by the first distributor via a bi-directional communications channel, the second control information containing contract information for updating;
• an update device configured to periodically update at a first period the contract information of the first control information in the storage device to the contract information of the second control information;
• a certifying device configured to send back a receipt acknowledgement via the bi-directional communications channel when the contract information of the first control information is updated;
• a second receiver configured to periodically receive encrypted key information broadcasted by the second distributor at a second period shorter than the first period, the encrypted key information being required to decrypt the contents information, the encrypted key common to all broadcast receiving apparatuses and encrypted by the work key;
• a key decrypting device configured to decrypt the encrypted key information to obtain decrypted key information and store the decrypted key information in the storage device;
• a determination device configured to determine whether the stored decrypted key information is valid based on the contract information;
• and
• a contents decrypting device configured to decrypt the contents information based on the decrypted key information that has been determined to be valid.

A broadcast receiving apparatus communicating with a first distributor which performs bi-directional communications, and a second distributor which performs a broadcast transmission, comprising:

• a storage device configured to store first control information containing identification information and contract information, the first control information including contract information for selecting some of a plurality of different channels, the first control information required to decrypt encrypted contents information broadcasted by the second distributor, and the contract information including a work key encrypted by a master key;
• a first receiver configured to receive second control information distributed by the first distributor via a bi-directional communications channel, the second control information containing contract information for updating;
• an update device configured to periodically update at a first period the contract information of the first control information in the storage device to the contract information of the second control information;
• a certifying device configured to send back a receipt acknowledgement via the bi-directional communications channel when the contract information of the first control information is updated;
• a second receiver configured to periodically receive encrypted key information broadcasted by the second distributor at a second period shorter than the first period, the encrypted key information being required to decrypt the contents information, the key information common to all broadcast receiving apparatuses and encrypted by the work key;
• a key decrypting device configured to decrypt the encrypted key information to obtain decrypted key information and store the decrypted key information in the storage device:
• a determination device configured to determine whether the stored decrypted key information is valid based on the contract information;
• and
• a contents decrypting device configured to decrypt the contents information based on the decrypted key information that has been determined to be valid and updated contract information of the first control information.

An information receiving apparatus which communicates with first and second distributors, comprising:

• a storage device configured to store first control information required to decrypt broadcasted and encrypted contents information, the first control information containing identification information unique to the receiving apparatus and contract information for selecting some of different channels, the first control information required for the receiving apparatus to select broadcasted and encrypted contents information, the contract information including a work key encrypted by a master key;
• a first receiver configured to receive second control information distributed from the first distributor via a bi-directional communication channel, the second control information containing contract information used to update at least contract information of the first control information stored in the storage device or broadcasted by the first distributor;
• a transmitter configured to transmit receipt of the information when the first receiver receives the second control information via the bi-directional communications channel;
• an update device configured to periodically update at a first period the contract information of the first control information in the storage device to the contract information of the second control information received by the first receiver;
• a certifying device configured to send back a receipt acknowledgement via the bi-directional communications channel when the contract information of the first control information is updated;
• a second receiver configured to periodically receive encrypted key information broadcasted by the second distributor, the encrypted key information being required to decrypt the encrypted contents information and common to a plurality of broadcast receiving apparatuses at a second period shorter than the first period, the encrypted key information being encrypted by the work key;
• a key decrypting device configured to decrypt the encrypted key information to obtain decrypted key information and store the decrypted key information in the storage device;
• a determination device configured to determine whether the stored decrypted key information is valid based on the contract information;
• and
• a contents decrypting device configured to decrypt the contents information based on the decrypted key information that has been determined to be valid.