Distribution of digital content protected by watermark-generating password
A receiver receives digital content scrambled using a control word and a user code for the scrambled content. A user inputs the user code that is forwarded to a code extractor that generates the control word and a user identifier from it. The control word is sent to a descrambler, a watermark information generator and a visible watermark insertion unit. The descrambler descrambles the scrambled content using the control word, an invisible watermark insertion unit inserts invisible watermark information obtained from the watermark information generator into the descrambled content and the visible watermark insertion unit inserts the user identifier as a visible watermark. Also provided are a corresponding method for processing digital content and a method and a device for generating the user code.
1. A method of processing digital content, the method comprising:
receiving, by at least one processor, content scrambled using a control word;
receiving, via a user interface, a user code, wherein a user identifier and the control word are concatenated and encrypted in the user code based on a secret key;
decrypting, by the at least one processor, the control word and the user identifier from the user code using the secret key;
descrambling, by the at least one processor, the scrambled content using the control word;
generating, by the at least one processor, a watermark based on the user identifier such that the watermark is uniquely associated with the user identifier;
inserting, by the at least one processor, the watermark into the descrambled content; and
outputting, by the at least one processor, the watermarked content, wherein the decrypting comprises:
obtaining, by the at least one processor, an intermediate code from the user code; and
decrypting, by the at least one processor, the control word and the user identifier from the intermediate code.
2. The method of claim 1 , wherein the watermark is an invisible watermark.
3. The method of claim 1 , further comprising inserting, by the at least one processor, the user identifier as a visible watermark.
4. A device for processing digital content, the device comprising a processor configured to:
receive content scrambled using a control word;
receive, via a user interface, a user code, wherein a user identifier and the control word are concatenated and encrypted in the user code based on a secret key;
decrypt the user identifier and the control word from the user code using the secret key;
descramble the scrambled content using the control word;
generate a watermark based on the user identifier such that the watermark is uniquely associated with the user identifier;
insert the watermark into the descrambled content; and
output the watermarked content, wherein the decrypt comprises the processor configured to:
obtain an intermediate code from the user code; and
decrypt the control word and the user identifier from the intermediate code.
5. The device of claim 4 , wherein the watermark is an invisible watermark.
6. The device of claim 4 , wherein the processor is further configured to insert the user identifier as a visible watermark.
7. The method of claim 1 , wherein the user code is a text string.
8. The device of claim 4 , wherein the user code is a text string.