| 摘要 |
Data is protected from unauthorized copying by rescrambling an unauthorized version of the data, but descrambling an authorized version of the data. This is done using a trigger signal. The trigger signal is embbeded into the data to form watermarked data. The possibly protected data or watermarked data is converted to possibly usable data by extracting the trigger signal and checking the value as show in the figure. The possibly protected data is passed through a descrambler (30), where the trigger signal, if present, is extracted. A descrambling key and a descrambling algorithm (40) are applied to the possibly protected data if the trigger signal is present, but not applied to the possibly protected data if the trigger signal is not present. One property of the trigger signal is that it is preserved through signal transformation, such as one or more compression, decompression, analog to digital conversion, and digital to analog conversion. As a result of this property the trigger signal can be detected in either scrambled or descrambled data. |
