Method and apparatus for accessing stored digital programs

• US 6,363,149 B1
• Filed: 10/01/1999
• Issued: 03/26/2002
• Est. Priority Date: 10/01/1999
• Status: Expired due to Term

• Current Assignee: Carol Maxwell, Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Candelore, Brant L.
• Primary Examiner(s): Hayes, Gail
• Assistant Examiner(s): Smithers, Matthew
• Application Number:
  US09/410,681
• Time in Patent Office: 907 Days
• Field of Search: 380/45, 380/239, 380/240, 380/241, 380/242, 380/201, 380/202, 705/51, 705/57
• US Class Current: 380/45
• CPC Class Codes: H04N 7/163 by receiver means only

Abstract

A method for deriving past keys by using a one way function to relate an ordered sequence of keys to each other. In one embodiment, a method provides future access keys by creating a plurality of entitlement control messages, each entitlement control message including an access key for a given time period. In another embodiment, a method provides future access keys by creating an entitlement control message having a plurality of access keys corresponding to a plurality of time periods. In another embodiment, a method tracks an entitlement history by creating an entitlement management message having an entitlement time history field that includes information about whether a user has entitlement to view content recorded during a past time period. In another embodiment, the invention authorizes access to stored digital programs by determining whether a program is old, determining whether a user is authorized to view the old program, and if the user is not authorized, asking the user whether the user wants to access old programs, if the user wants to access old programs, displaying a plurality of payment options to the user.

Claims

1. A method for deriving at least one key of a plurality of keys used to descramble scrambled data comprising:

receiving the scrambled data at a conditional access device;

receiving at least one of the keys of the plurality of keys and a one way function at the conditional access device, wherein the plurality of keys are related to each other in an ordered sequence based on the one way function;

deriving at least one additional key from the received key and the one way function without requiring storage of multiple keys;

using the additional key to descramble the received scrambled data in the conditional access device; and

after a predetermined time period, deriving another key using the additional key and the one way function.

2. The method of claim 1, wherein the ordered sequence of keys starts with a first key and ends with a last key.

3. The method of claim 1, wherein the one way function and a given key in the ordered sequence can derive previous keys in the ordered sequence.

4. The method of claim 3, wherein the previous keys that can be derived include the keys from the first key to the given key.

5. The method of claim 1, wherein the one way function and a given key in the ordered sequence cannot derive subsequent keys in the ordered sequence.

6. The method of claim 5, wherein the subsequent keys that cannot be derived include all keys following the given key in the ordered sequence, up to and including the last key.

7. The apparatus of claim 5, wherein the subsequent keys that cannot be derived include all keys following the given key in the ordered sequence, up to and including the last key.

8. An apparatus for deriving at least one key of a plurality of keys used to descramble scrambled data comprising:

a receiver configured to receive the scrambled data at a conditional access device, and configured to receive at least one of the keys of the plurality of keys and a one way function at the conditional access device, wherein the plurality of keys are related to each other in an ordered sequence based on the one way function; and

a processor connected to the receiver, the processor configured to derive at least one additional key from the received key and the one way function, configured to use the additional key to descramble the received scrambled data in the conditional access device wherein storage of multiple keys is not required; and

to derive another key using the additional key and the one way function after a given time period has expired.

9. The apparatus of claim 8, wherein the ordered sequence of keys starts with a first key and ends with a last key.

10. The apparatus of claim 8, wherein the processor is configured to use the one way function and a given key in the ordered sequence to derive previous keys in the ordered sequence.

11. The apparatus of claim 8, wherein the one way function and a given key in the ordered sequence cannot derive subsequent keys in the ordered sequence.

12. The apparatus of claim 11, wherein the previous keys that can be derived include the keys from the first key to the given key.

13. An apparatus for deriving at least one of a plurality of keys used to descramble scrambled data comprising:

means for receiving the scrambled data at a conditional access device;

means for receiving at least one key of the keys of the plurality of keys and the one way function at the conditional access device, wherein the plurality of keys are related to each other in an ordered sequence based on the one way function;

means for deriving at least one additional key from the received key and the one way function, wherein storage of multiple keys is not required;

means for using the additional key to descramble the received scrambled data in the conditional access device; and

means for deriving another key using the additional key and the one way function.

14. A computer readable medium containing executable instructions, which, when executed in a processing system, causes the system to perform the steps for deriving at least one key of a plurality of keys used to descramble scrambled data comprising:

receiving the scrambled data at a conditional access device;

receiving at least one of the keys of a plurality of keys and a one way function at the conditional access device, wherein the keys are related to each other in an ordered sequence based on the one way function;

deriving at least one additional key from the received key and the one way function, wherein storage of multiple keys is not required;

using the derived key to descramble the received scrambled data in the conditional access device; and

after a predetermined time period, deriving another key using the additional key and the one way function.