A method for communication, including distributing over a communication network multiple channels of digital content, which are encrypted using different, channel-specific control words, and transmitting over the communication network, different, channel-specific entitlement control messages from which the control words are derivable such that each of the different channel-specific control words is derivable from any of the different channel-specific entitlement control messages by authorized receivers of the channels on the communication network. Related methods and apparatus are also included.