Key Derivation for Secure Communications

• US 20120084806A1
• Filed: 09/30/2010
• Published: 04/05/2012
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Original Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Inventors: Fahrny, James W., Kuykendall, Pete, Davoust, Nancy
• Granted Patent: US 10,193,873 B2
• Time in Patent Office: Days
• US Class Current: 725/31
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00478 wherein contents are decrypted and re-encrypted with a different key when being copied from/to a record carrier
• CPC Class Codes: H04L 2463/061 applying further key derivation, e.g. deriving traffic keys from a pair-wise master key cryptographic mechanisms or cryptographic arrangements for generation of secret information including derivation or calculation of cryptographic keys or passwords H04L9/0861
• CPC Class Codes: H04L 2463/101 applying security measures for digital rights management data processing systems or methods, specially adapted for commerce, e.g. marketing, shopping, billing, auctions or e-commerce G06Q30/00
• CPC Class Codes: H04L 63/06 for supporting key management in a packet data network cryptographic mechanisms or cryptographic arrangements for key management H04L9/08
• CPC Class Codes: H04L 63/068 using time-dependent keys, e.g. periodically changing keys cryptographic mechanisms or cryptographic arrangements for controlling usage of secret information H04L9/088
• CPC Class Codes: H04L 9/30 Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy

Abstract

A security system is disclosed in which a device-specific key value is provided to a security processing device, and then used to derive additional derived keys for use in secured communications. In response to identifying a compromise of the derived keys, the system can be instructed to derive new or replacement derived keys for use in the secured communications. In some embodiments, the security system can be used in a video reception device, to decrypt encrypted video content.

Claims

1. A security device, comprising:

a first memory storage storing a device security key; and

a first processor configured to;

encrypt the device security key using a first seed value to derive a first derived key, and store the first derived key in a second memory storage area of the device; and

in response to a compromise of the first derived key, re-encrypt the device security key using a second seed value to derive a second derived key, and store the second derived key in the second memory storage of the device.

2. The device of claim 1, further comprising an external interface configured to communicate with an external security processor, wherein the first processor is further configured to perform the following:

establish a secure communication session with the external security processor; and

use the secure communication session to transmit the first derived key to the external security processor.

3. The device of claim 2, wherein the external security processor is configured to decrypt and process encrypted video using the first derived key.

4. The device of claim 2, wherein the processor is further configured to terminate the secure session in response to the compromise, and to use the second derived key with a replacement external security processor.

5. The device of claim 2, wherein the external security processor comprises a smart card.

6. The device of claim 1, wherein the device is a video content reception device.

7. The device of claim 1, wherein the first memory storage area is a one-time programmable memory.

8. The device of claim 1, wherein the first memory storage area and second memory storage area are physically separate memories.

9. The device of claim 1, wherein the first and second memory storage areas include different types of security protection.

10. The device of claim 9, wherein the first and second memory storage areas are encrypted with different encryption keys.

11. The device of claim 1, wherein the processor is configured to receive the second seed value from an external source.

12. The device of claim 1, wherein the device security key is unique to the device.

13. The device of claim 1, wherein the device security key is common to a plurality of other devices, and wherein the processor is further configured to derive the second derived key in response to a global compromise of the first derived key.

14. A security method, comprising:

encrypting, by a computing processor, a device key stored in a device'"'"'s first memory to derive a first derived key for the device;

using the first derived key for multiple communication sessions involving the device; and

in response to a key compromise, performing a second encryption of the device key to derive a second derived key for the device, the second derived key being different from the first derived key.

15. The method of claim 14, further comprising:

instructing a plurality of computing processors on a plurality of different devices to encrypt a common global device key to derive a common global derived key for the plurality of different devices;

determining that a compromise of the common global derived key has occurred;

identifying a subset of the plurality of different devices as being affected by the compromise; and

instructing the computing processors in the subset of devices to encrypt the common global device key a second time, to derive a second global derived key for the subset of devices.

16. The method of claim 15, comprising:

further splintering the subset into two or more smaller subsets in response to a second key compromise, and instructing one of the smaller subsets to derive a third derived key for the smaller subset.

17. The method of claim 14, wherein the computing processor is part of a portable security device removably attached to a content access device.

18. The method of claim 14, further comprising transmitting a report of a pairing between the device and another device to a service provider, and dissolving the pairing in response to a compromise of the first derived key.

19. The method of claim 14, further comprising limiting use of the derived key to the device.

20. The method of claim 14, further comprising limiting use of the derived key to an authorized pair of devices comprising the device and a second device.