Abstract: In a method of receiving packets of data addressed to one or more receivers each having an individual identifier, wherein the data is included in a digital signal having destination addresses successively encrypted from a sequence of control words and receiver identifiers, and control messages containing the control words in encrypted form, address flags and control flags. The method processes the control messages to construct receiver addresses from the control words and the receiver identifier; directs the receiver addresses to update a receiver address register selected by the associated control flag in response to the transmitted control flags; directs each destination address to be compared with the receiver address to one of the address registers selected by the associated address flag in response to the address flags and; accepts each packet of data having a destination address matching the receiver address to which it was compared.