Patent ID: 6393128
Filing Date: 2002-05-21
Classification: H04L,H04N

Abstract:
A system for broadcasting data signals in a secure manner, comprising means for encrypting the data signals using a first key, means for broadcasting the encrypted data signals to subscribers, means for decrypting the encrypted data signals at each of the subscribers using the first key, means for encrypting the first key using a second key, said second key being different for each group of subscribers having a common interest in a type of programs, means for broadcasting the encrypted first key to all subscribers, means for decrypting the encrypted first key at each of the subscribers using the second key, characterized in that said second key is a combination of a key common to all subscribers and a difference key which is unique per type of programs, where means are provided for encrypting the common key and for broadcasting the encrypted common key to all subscribers and means for decrypting the encrypted common key at each of the subscribers.