H04N 21/26609

Channel or content management, e.g. generation and management of keys and entitlement messages in a conditional access system, merging a VOD unicast channel into a multicast channel {for generating or managing entitlement messages, e.g. Entitlement Control Message [ECM] or Entitlement Management Message [EMM] using retrofitting techniques, e.g. by re-encrypting the control words used for pre-encryption}