Watermarking of digital object
AssigneeHewlett-Packard Development Company, L.P.
InventorBalas K. Natarajan
Life of this patent
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Abstract
A technique for identifying digital object using a digital watermark. The technique includes the steps of encrypting a message derived from source data on the digital object, to obtain an encrypted message digest (S); deriving a watermark from the encrypted message digest (S); and incorporating the watermark into the source data. The encryption is preferably done with a public key encryption system. The message to be encrypted can be obtained via performing a hash function on the source data on the digital object to obtain a message digest (M). The message digest (M) is the message encrypted with the signature encryption key to obtain the encrypted message digest (S). The watermark is resistant to cropping, scaling, and truncation.
Claims14
A system for identifying a digital object using a digital watermark, comprising:
- means for obtaining a set of source data from the digital object, the source data comprising a set of data values;
- means for generating a message digest by applying a function to the source data which is preselected to avoid reconstruction of the source data from the message digest;
- means for encrypting the message digest to obtain an encrypted message digest;
- means for deriving a watermark vector from the encrypted message digest;
- means for determining an average vector of a selected subset of the data values;
- means for avoiding a dependency between the watermark vector and the average vector by orthogonalizing the watermark vector with respect to the average vector;
- means for combining the watermark vector with the selected subset of the data values of the source data to obtain a watermarked object that includes the digital watermark.
An article of manufacture comprising a program storage medium, tangibly embodying a program code means readable by a computer to cause the computer to identify a digital object using a digital watermark, comprising:
- code means for obtaining a set of source data from the digital object, the source data comprising a set of data values;
- code means for generating a message digest by applying a function to the source data which is preselected to avoid reconstruction of the source data from the message digest;
- code means for encrypting the message digest to obtain an encrypted message digest;
- code means for deriving a watermark vector from the encrypted message digest;
- code means for determining an average vector of a selected subset of the data values;
- code means for avoiding a dependency between the watermark vector and the average vector by orthogonalizing the watermark vector with respect to the average vector;
- code means for combining the watermark vector with the selected subset of the data values of the source data to obtain a watermarked object that includes the digital watermark.
A method for identifying a digital object, comprising the steps of
- deriving a watermark vector from the digital object;
- determining an average vector of a selected subset of the digital object;
- avoiding a dependency between the watermark vector and the average vector by orthogonalizing the watermark vector with respect to the average vector;
- combining the watermark vector and the digital object.
A method for identifying a digital object, comprising the steps of:
- deriving a watermark vector from the digital object;
- determining an average vector of a selected portion of the digital object;
- avoiding a dependency between the watermark vector and the digital object by orthogonalizing the watermark vector with respect to the average vector;
- combining the watermark vector with the digital object.
Dependencies are inferred from the claim text.