A method of preparing digital content for transmission to a plurality of receivers, the digital content comprising a sequence of content portions, comprising: at a pre-processor, generating at least first and second copies of selected ones of said content portions; at a content protection and content packaging system: distributing each of the at least first and second copies of each selected content portion in encrypted form into a separate group of transport stream packets, each of the at least first and second copies of each selected content portion distributed into transport stream packets being differently encrypted to each other; merging all of the said transport stream packets for each selected content portion into an original transport stream in which at least some of the transport stream packets deriving from the same content portion but being differently encrypted are interleaved; and marking the transport stream packets containing each of the differently encrypted copies of a content portion with a different corresponding stream label visible in the packets of the original transport stream; at a post-processor, filtering transport stream packets in the original transport stream according to a stream label and reordering the original transport stream to form a re-multiplexed transport stream in which transport stream packets containing parts of the same content portion but being differently encrypted are not interleaved. at a pre-processor, generating at least first and second copies of selected ones of said content portions; at a content protection and content packaging system: distributing each of the at least first and second copies of each selected content portion in encrypted form into a separate group of transport stream packets, each of the at least first and second copies of each selected content portion distributed into transport stream packets being differently encrypted to each other; merging all of the said transport stream packets for each selected content portion into an original transport stream in which at least some of the transport stream packets deriving from the same content portion but being differently encrypted are interleaved; and marking the transport stream packets containing each of the differently encrypted copies of a content portion with a different corresponding stream label visible in the packets of the original transport stream; distributing each of the at least first and second copies of each selected content portion in encrypted form into a separate group of transport stream packets, each of the at least first and second copies of each selected content portion distributed into transport stream packets being differently encrypted to each other; merging all of the said transport stream packets for each selected content portion into an original transport stream in which at least some of the transport stream packets deriving from the same content portion but being differently encrypted are interleaved; and marking the transport stream packets containing each of the differently encrypted copies of a content portion with a different corresponding stream label visible in the packets of the original transport stream; at a post-processor, filtering transport stream packets in the original transport stream according to a stream label and reordering the original transport stream to form a re-multiplexed transport stream in which transport stream packets containing parts of the same content portion but being differently encrypted are not interleaved.