| 摘要 |
A system for producing a output scrambled digital data stream from a input scrambled digital data stream. The input scrambled digital data stream includes a plurality of control messages (ECMs), each ECM including coded information for generating a control word (CW) associated with the ECM and being encoded using a ECM key. The input scrambled digital data stream also includes a plurality of segments of scrambled digital data, each segment of scrambled digital data being associated with one of the plurality of ECMs and being scrambled using the CW associated with the ECM. A method for producing the output scrambled digital data stream includes replacing each of the plurality of ECMs with a corresponding transformed ECM (TECM), each corresponding TECM comprising coded information for generating the CW associated with the corresponding ECM and being encoded using a TECM key, thus producing the output scrambled digital data stream. The ECM key is replaced with a new ECM key at a ECM key change time, and the TECM key is not replaced at the ECM key change time. |
