Patent ID: 7949135
Filing Date: 2011-05-24
Classification: H04L

Abstract:
1. A method for improved key distribution in a broadcast data communication system for selective access to services, wherein a group key management message, including a service access key, is transferred to a group of users for access to a selected service, said method comprising: creating a set of encryption keys based on a stateless subset cover scheme, each user being associated with a leaf in said stateless subset cover scheme; establishing a state key and a corresponding state representing a subset of users that have the state key and a subset of users that do not have the state key; determining a subset cover based on information representative of the established state; and determining said group key management message at least partly based on the determined subset cover, wherein said group key management message M is determined according to: where T is a state identifier, K the broadcast data communication system transferring said group key management message to the group of users for access to the selected service.