Digital Content Protection Method and Apparatus

• US 20020099948A1
• Filed: 09/06/2001
• Published: 07/25/2002
• Est. Priority Date: 09/02/1999
• Status: Active Grant

• Current Assignee: Cryptography Research, Inc. (Rambus Inc.)
• Original Assignee: Cryptography Research, Inc. (Rambus Inc.)
• Inventors: Kocher, Paul C., Jun, Benjamin C., Jaffe, Joshua M.
• Granted Patent: US 6,640,305 B2
• Time in Patent Office: Days
• US Class Current: 713/194
• CPC Class Codes: G06F 21/107 License processing; Key processing
• CPC Class Codes: G06F 21/602 Providing cryptographic facilities or services
• CPC Class Codes: G06F 21/72 in cryptographic circuits
• CPC Class Codes: G06F 2211/007 Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
• CPC Class Codes: G06F 2221/2101 Auditing as a secondary aspect
• CPC Class Codes: G06Q 20/367 involving electronic purses or money safes
• CPC Class Codes: H04L 2209/127 Trusted platform modules [TPM]
• CPC Class Codes: H04L 2209/603 Digital right managament [DRM]
• CPC Class Codes: H04L 9/0833 involving conference or group key network architectures or network communication protocols for key management in group communication in a packet data network H04L63/065

Abstract

Abstract of Disclosure

Before use, a population of tamper-resistant cryptographic enforcement devices is partitioned into groups and issued one or more group keys. Each tamper-resistant device contains multiple computational units to control access to digital content. One of the computational units within each tamper-resistant device communicates with another of the computational units acting as an interface control processor, and serves to protect the contents of a nonvolatile memory from unauthorized access or modification by other portions of the tamper-resistant device, while performing cryptographic computations using the memory contents. Content providers enforce viewing privileges by transmitting encrypted rights keys to a large number of recipient devices. These recipient devices process received messages using the protected processing environment and memory space of the secure unit. The processing result depends on whether the recipient device was specified by the content provider as authorized to view some encrypted digital content. Authorized recipient devices can use the processing result in decrypting the content, while unauthorized devices cannot decrypt the content. A related aspect of the invention provides for securing computational units and controlling attacks. For example, updates to the nonvolatile memory, including program updates, are supported and protected via a cryptographic unlocking and validation process in the secure unit, which can include digital signature verification.

Claims

1. A method for processing a cryptographic secret distributed to a plurality of tamper-resistant devices among a group of devices sharing a group secret but having individually-assigned group offsets, said method comprising the steps of:

2. The method of claim 1 where said memory is protected to prevent unauthorized access.

3. The method of claim 2 where said unauthorized access includes unauthorized reading.

4. The method of claim 2 where said unauthorized access includes unauthorized modification.

5. The method of claim 2 where said memory is nonvolatile.

6. The method of claim 2 where said memory is encrypted.

7. The method of claim 2 where:

8. The method of claim 1 where:

9. The method of claim 1 where said input value is encrypted, and comprising the additional step of decrypting said encrypted input value.

10. The method of claim 1 comprising the additional steps of:

11. The method of claim 1 where said step (d) includes updating a failure counter stored in a nonvolatile memory.

12. A method for processing a cryptographic secret distributed to a plurality of tamper-resistant devices among a group of devices sharing a group secret but having individually-assigned group offsets, said method comprising the steps of:

13. The method of claim 12 where:

14. The method of claim 12 where said step (c) includes the substep of combining said individually-assigned group offset corresponding to said recipient offset and said group mask to produce an intermediate result, where said intermediate result is equal to said group mask if and only if said recipient device is contained in said plurality.

15. The method of claim 12 where said subsequent cryptographic operation is used to decode digital content.

16. The method of claim 12 where said subsequent cryptographic operation is used to derive a key that enables the decryption of an encrypted television signal.

17. The method of claim 12 where said party from which said input value is received:

18. The method of claim 17 where:

19. The method of claim 17 where said broadcast channel is a cable television system.

20. The method of claim 17 where said broadcast channel includes broadcast distribution over a computer network.

21. The method of claim 12, where:

22. A device for controlling access to digital content, said device comprising:

23. The device of claim 22:

24. The device of claim 23 where:

25. The device of claim 22 where said second microprocessor includes logic for decrypting said data received from said first microprocessor.

26. The device of claim 25 where said second microprocessor includes logic for determining whether data output by said decryption logic contains a code update request.

27. A method for receiving a cryptographic secret at a recipient device within a plurality of tamper-resistant devices each having individually-assigned group offsets but sharing a group secret, said method comprising:

28. The method of claim 27 where said step (c)(i) includes:

29. A recipient device for processing a cryptographic secret distributed to a plurality of tamper-resistant devices among a group of devices sharing a group secret but having individually-assigned group offsets, said processing device comprising: