Authentication of physical and electronic media objects using digital watermarks
First Claim
1. A method for encoding auxiliary data into a host signal comprising:
- computing a content specific message dependent on the host signal;
encoding the content specific message into a watermark signal;
embedding the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal.
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Abstract
Digital watermark methods for encoding auxiliary data into a host signal are used to authenticate physical and electronic objects. One such method computes a content specific message dependent on the host signal, encodes the content specific message into a watermark signal, and embeds the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal. One specific implementation embeds data representing salient features of the host signal into the watermark. For example, for photo IDs, the method embeds the spatial location of salient features of the photo into the watermark. Another implementation computes a semi-sensitive hash of the host signal, such as a low pass filtering of the signal, and embeds the hash into the watermark. The watermark signal may be content dependent by making the watermark key dependent on some attribute of the signal in which the watermark is embedded. Another approach is to make the watermark key dependent on a user or an attribute of the user. Yet another approach is to use multiple watermark components and multiple watermark detection stages that help identify and screen out invalid watermark signals. Another digital watermarking method for authenticating a media object transforms a media signal to a frequency domain comprising an array of frequency coefficients. It selects a first set of frequency coefficients, and alters the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern. The pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern.
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Citations
45 Claims
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1. A method for encoding auxiliary data into a host signal comprising:
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computing a content specific message dependent on the host signal; encoding the content specific message into a watermark signal; embedding the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 22)
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13. A method for authenticating a media object comprising:
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transforming a media signal to a frequency domain comprising an array of frequency coefficients; selecting a first set of frequency coefficients; altering the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern;
wherein the pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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23. An identification document including:
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a first image embedded with watermark data and printed on the document; wherein a copy of the first image is embedded with watermark data, and is referenced on the document or encoded into the document; and wherein the watermark data embedded in the first image and the copy is related in a manner that enables validity of the document to be verified. - View Dependent Claims (24, 25, 26, 27)
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28. A method for encoding auxiliary data into a host signal comprising:
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computing a content specific message dependent on the host signal; encoding the content specific message into a watermark signal; embedding the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal; wherein the content specific message includes data representing locations of one or more salient features of the host signal. - View Dependent Claims (29, 30, 31)
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32. A method for authenticating a media object comprising:
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transforming a media signal to a frequency domain comprising an array of frequency coefficients; selecting a first set of frequency coefficients; altering the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern;
wherein the pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern;for each coefficient in the first set, selecting a corresponding coefficient in a corresponding set, and changing values of the coefficients in the first set and the corresponding coefficients in the corresponding set such that the differences between the coefficient values in the first set and the corresponding set form a desired delta pattern. - View Dependent Claims (33, 34)
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35. A method of encoding a plural symbol auxiliary message into content, comprising:
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(a) processing received input content to yield characteristic information related thereto; (b) defining a plural symbol auxiliary message that includes said characteristic information yielded from the input content; (c) performing an algorithmic transformation on said plural symbol auxiliary message to yield a watermark signal; and (d) processing the input content to steganographically convey the watermark signal, yielding encoded content. - View Dependent Claims (36, 37, 38, 39, 40, 41)
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- 42. In a method of digitally watermarking content, the method including performing an algorithmic transformation on a plural symbol auxiliary message to yield a watermark signal, and altering the content in accordance with said watermark signal, an improvement comprising deriving at least certain symbols of said auxiliary message from data representing the content.
Specification