US 6,888,944 B2 · Method for assigning encryption keys

Abstract

Sets of encryption keys useful by devices for decrypting encrypted content are defined using an error-correcting code such as a Reed-Solomon code to define vectors of length “n” over an alphabet of (0, . . . , N−1), wherein “n” is the number of columns in a key matrix and “N” is the number of rows in the matrix. Each vector represents a set of keys that can be assigned to a device. With this invention, overlap between sets of keys can be minimized to minimize the possibility that the key set of an innocent device might be inadvertently revoked when the key set of a compromised device is revoked. Also, only the generating matrix of the error-correcting code and the index of one set of keys need be stored in memory, since all previously defined key sets can be regenerated if need be from just the generating matrix and index.

Claims24

Dependent claims

A method for defining sets of encryption keys from a key matrix, comprising:

receiving at least one parameter representing a characteristic of the key matrix;
using the parameter and an error-correcting code, defining plural sets of keys;
and assigning at least some sets of keys to at least some respective devices, wherein the receiving act includes receiving at least a row parameter “N” representing the number of rows in the key matrix and a column parameter “n” rep resenting the number of columns in the key matrix, and the method further includes:
using an error-correcting code having a Hamming distance “d” that minimizes key overlap between sets of keys.

1 more element

Dependencies are inferred from the claim text.

Facts

Application

09/777,506Filed 5 Feb 2001 · continuation in part

Priority

24 Apr 1998

Published

US 2002/0106087 A18 Aug 2002

Granted

3 May 2005

Term ends

Not estimatedThe source records don’t support an estimate.

Classification12 codes

H04N 7/163
Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing: by receiver means only
H04L 9/0861
Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords: generation of secret information…
H04L 9/14
Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols: using a plurality of keys…
H04N 7/1675
Systems rendering the television signal unintelligible and subsequently intelligible: providing digital key or authorisation information for…

Method for assigning encryption keys

Life of this patent

Method for assigning encryption keys

Life of this patent

Abstract

Claims24