Method and apparatus for preventing removal of embedded information in cover signals
First Claim
1. A method for embedding watermark information into a cover signal, comprising the steps of:
- selecting values of predefined phase modulation parameters for said cover signal;
modulating the phase of said cover signal according to said selected phase modulation parameter values to obtain a phase-modulated cover signal; and
embedding said watermark information into said phase-modulated cover signal to obtain a stego signal;
whereinsaid phase modulation parameter values are selected such that combining any two or more instances of said stego signal containing different watermark information will result in phase cancellation with respect to the combined signal.
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Abstract
Apparatus and methods are provided for embedding watermark information into a cover signal, such as an audio signal, video signal, or still image signal, in a manner that prevents the watermark information from being removed without degrading the quality of the cover signal. This is accomplished by subjecting the cover signal to a phase modulation prior to being embedded with the watermark information, wherein the amount or degree of phase modulation is changed at least for each different watermark to be embedded in a particular instance or copy of the cover signal. As such, if two copies of the same cover signal, each containing a different watermark, are averaged or combined in an attempt to obliterate the watermark information, the cover signal will be subjected to phase cancellation, rendering any illicit copy of such signal so derived to be valueless.
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Citations
19 Claims
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1. A method for embedding watermark information into a cover signal, comprising the steps of:
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selecting values of predefined phase modulation parameters for said cover signal; modulating the phase of said cover signal according to said selected phase modulation parameter values to obtain a phase-modulated cover signal; and embedding said watermark information into said phase-modulated cover signal to obtain a stego signal;
whereinsaid phase modulation parameter values are selected such that combining any two or more instances of said stego signal containing different watermark information will result in phase cancellation with respect to the combined signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for embedding watermark information into a cover signal, comprising:
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a phase modulation parameter generator for providing values of predefined phase modulation parameters; a phase modulator for modulating the phase of said cover signal in accordance with said phase modulation parameter values to produce a phase-modulated cover signal; and a watermark information embeddor for embedding watermark information into said phase-modulated cover signal to obtain a stego signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method for preventing removal of watermark information embedded into a cover signal, comprising the steps of:
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modulating the phase of said cover signal by an amount which varies at least as a function of the content of said watermark information, to produce a phase-modulated cover signal; and embedding said watermark information into said phase-modulated cover signal. - View Dependent Claims (16, 17, 18, 19)
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Specification