A method and system of preventing control word sharing, the method and system including receiving a temporal key, denoted TKi, at a removable security element, receiving an entitlement control message (ECM), the ECM including a control word derivable by the removable security element, deriving the control word from the ECM at the removable security element, combining at least the control word and a value associated with an ID of the removable security element, thereby producing combined control word and removable security element ID data, encrypting the combined control word and removable security element ID data according to an encryption function, wherein the encrypting includes using TKi as an encryption key, and at a time after a removable security element interface has received TKi, but prior to a start of a crypto period with which the control word is associated, sending the encrypted combined control word and removable security element ID data to the removable security element interface. Related apparatus, methods and systems are also described.