A method of decrypting a scrambled digital data item at a client is disclosed, the method including: receiving actual control messages at the client, wherein each actual control message includes control word generating information for generating a control word associated with the actual control message; storing the actual control messages at the client; receiving the scrambled digital data item at the client independently of the actual control messages, wherein the scrambled digital data item includes a plurality of segments of scrambled digital data, each segment of scrambled digital data being associated with one of the actual control messages and being scrambled with the control word associated with the one of the actual control messages, and wherein the scrambled digital data item further includes a plurality of reference control messages, each segment of scrambled digital data comprising one of the reference control messages, each of the reference control messages including a control message reference value identifying the actual control message associated with the segment of scrambled digital data; and decrypting the scrambled digital data item using the plurality of actual control messages.