11. The method of claim 10 , further comprising: determining whether a packet of the first stream of packets is to be encrypted by the first control word or the second control word; and demultiplexing the first stream of packets, wherein the encrypting the first stream of packets with the first control word and the second control word comprises performing in parallel the encrypting with the first control word and the encrypting with the second control word.
11. The method of claim 10 , further comprising: determining whether a packet of the first stream of packets is to be encrypted by the first control word or the second control word; and demultiplexing the first stream of packets, wherein the encrypting the first stream of packets with the first control word and the second control word comprises performing in parallel the encrypting with the first control word and the encrypting with the second control word. 12. The method of claim 11 , further comprising: determining whether a packet of the first stream of packets is to be encrypted by the first control word or the second control word; and demultiplexing the first stream of packets to produce demultiplexed packets; adding a packet number to each demultiplexed packet; decrypting the demultiplexed packets with the first control word and the second control word by performing in parallel the decrypting with the first control word and the decrypting with the second control word.