Method for protecting content using watermarking
First Claim
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1. A method of copy protection for a document, comprising the steps of:
- generating a first digital string from the document to form a baseline watermark;
generating a second digital string from given text;
generating a watermark having a predetermined relationship to the first and second digital strings; and
inserting the watermark into the document to protect the document against illicit copying.
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Abstract
A watermarking procedure wherein each of a set of copies of the work has a slightly-modified form of a "baseline" watermark that is placed within a critical region of the data. The slight variations in the watermarks, however, are not perceptually visible and do not interfere with the work. If multiple persons collude to attempt to create an "illicit" copy of the work (i.e., a copy without a watermark), however, at least one of the modified watermarks is present in the copy, thereby identifying both the illicit copy and the copier.
488 Citations
37 Claims
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1. A method of copy protection for a document, comprising the steps of:
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generating a first digital string from the document to form a baseline watermark; generating a second digital string from given text; generating a watermark having a predetermined relationship to the first and second digital strings; and inserting the watermark into the document to protect the document against illicit copying. - View Dependent Claims (2, 3, 4, 5)
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6. An access control method, comprising the steps of:
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during a watermarking phase; generating a first digital string from an object sought to be protected to form a baseline watermark; generating a second digital string from given text; generating a watermark having a predetermined relationship to the first and second digital strings; and inserting the watermark into the object to protect access to the object; upon an access request; retrieving a derived watermark from the object to form a third digital string; generating a fourth digital string from the given text; correlating the third and fourth digital strings; and if the third and fourth digital strings have a predetermined correlation, authorizing access to the object. - View Dependent Claims (7)
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8. The method as described in 6 wherein the second and fourth digital strings are generated using a secret hash function.
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9. A method of watermarking an object, comprising the steps of:
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generating a first digital string from the object to form a baseline watermark; generating a second digital string from given text providing an indication that a first action with respect to the object is allowed and a second action with respect to the object is prohibited; generating a watermark having a predetermined relationship to the given text and the second digital string; and inserting the watermark into the object. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method for determining whether an object has a given watermark, comprising the steps of:
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processing the object to generate a data string; correlating the data string with a value that is a function of the given watermark and a second watermark such that information useful in determining the given watermark cannot be obtained from the value; and if the data string and the value correlate to a predetermined extent, indicating that the object has been watermarked with the given watermark. - View Dependent Claims (16)
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17. A method for determining whether a document has a given watermark vector embedded therein, comprising the steps of:
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processing the document to generate a data string; correlating the data string with a value that is a function of the given watermark vector and a second watermark, wherein the second watermark masks information about the given watermark; accepting the document as including the given watermark vector if the data string and the value correlate to a predetermined extent. - View Dependent Claims (18)
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19. A access protection method operative in a device having means for outputting given content, comprising the steps of:
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retrieving a derived watermark and a derived signal from the given content; generating a digital string from the derived signal using a secure hash function; correlating the derived watermark and the digital string; and based on a result of the correlating step, taking a given action. - View Dependent Claims (20, 21, 22)
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23. A method for authorizing access to given content that has a given watermark embedded therein, comprising the steps of:
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processing the given content to generate a first data string; generating a second data string by applying a given function to the first data string; correlating the first and second data strings; and if the first and second data strings correlate to a given degree, providing a password to enable further processing of the given content. - View Dependent Claims (24, 25)
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26. A method for computing a derived watermark, comprising the steps of:
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processing a given work W to form a first data string x1, x2, . . . xn, processing a collection C of works to form a second data string y1, y2, . . . yn ; and computing the derived watermark z1, z2, . . . zn by applying a given function f(xi, yi). - View Dependent Claims (27, 28, 29, 30)
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31. A method of access control for a document, comprising the steps of:
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generating a first digital string from the document to form a baseline watermark; generating a second digital string from given text; generating a set of watermarks each having a predetermined relationship to the first and second digital strings; and inserting the set of watermarks into the document to protect the document against illicit use. - View Dependent Claims (32, 33, 34, 35)
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36. A method for detecting a watermark in a document using information that, if disclosed, does not compromise security of the document, comprising the steps of:
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processing the document to generate a data string; correlating the data string with the information; and accepting the document as including the watermark if the data string and the information correlate to a predetermined extent. - View Dependent Claims (37)
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Specification