| 摘要 |
<p>A system (10) for scrambling / descrambling packets (20,22) of a stream of content (16) is disclosed, each of the packets (20,22) having a must stay clear (MSC) section (24) which is always kept in the clear, the system (10) comprising: an input handler (12) including: a receiving module (34) to receive the stream (16); and a mask module (46) to create, for each of the packets (20,22), a data mask (48) which includes all data of the MSC section except for at least one bit of data of the MSC section; and a scrambling / descrambling device (14) operationally associated with the input handler (12), the scrambling / descrambling device (14) including: a receiving module (50) to receive the data mask (48) for each of the packets (20,22) from the input handler (12); and an Initial Value module (52) to determine an Initial Value (70) for each of the packets (20,22) as a function of the data mask (48) of one of the packets (20,22) being processed such that the Initial Value (70) is not a function of the at least one bit of data of the MSC section (24) of the one packet (20,22) being processed, the scrambling /descrambling device (14) being adapted to at least one of scramble and descramble the packets (20,22) based on the Initial Value (70) and a Control Word (62).</p> |
