Digital watermarking by adding random, smooth patterns
First Claim
1. A method of marking, with an invisible identifier that cannot be removed therefrom, an electronic file containing a stream of samples comprising at least one image, which method comprises the steps of:
- selecting a first bit-string to represent authorship of said file;
selecting a second bit-string to represent content of said file;
combining said first and said second bit-string into said identifier;
applying a function to convert said identifier into a number in a range effective for seeding a pseudo-random number generator;
deriving a pseudo-random black and white pattern from said number by means of said generator,said pattern having dimensions substantially the same as said file;
processing said pattern to create a random collection of connected areas, thereby transforming said pattern'"'"'s spectral energy to lower frequencies;
smoothing said pattern;
rescaling said smoothed pattern so that its amplitude is more than one unit sample; and
adding said rescaled, smoothed pattern to said file, whereby said file is marked with said identifier.
1 Assignment
0 Petitions
Accused Products
Abstract
A digital image is "watermarked", that is, authenticated by an embedded pattern. The pattern is created by hashing the image and adding a signature element. Manipulating this result by the seed for a random number generator leads to an initial two dimensional random black-and-white pattern. This pattern is manipulated by a cellular automaton and smoothed before being added to the original image. To determine whether the image is authentic, one retrieves the watermark by subtracting the watermarked image from the original to obtain the difference. The value of the correlation between the difference thus obtained and the smoothed pattern determines the presence or absence of the watermark.
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Citations
22 Claims
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1. A method of marking, with an invisible identifier that cannot be removed therefrom, an electronic file containing a stream of samples comprising at least one image, which method comprises the steps of:
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selecting a first bit-string to represent authorship of said file; selecting a second bit-string to represent content of said file; combining said first and said second bit-string into said identifier; applying a function to convert said identifier into a number in a range effective for seeding a pseudo-random number generator; deriving a pseudo-random black and white pattern from said number by means of said generator, said pattern having dimensions substantially the same as said file; processing said pattern to create a random collection of connected areas, thereby transforming said pattern'"'"'s spectral energy to lower frequencies; smoothing said pattern; rescaling said smoothed pattern so that its amplitude is more than one unit sample; and adding said rescaled, smoothed pattern to said file, whereby said file is marked with said identifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of determining whether or not an electronic file containing at least one image also contains an invisible identifier, which method comprises the steps of:
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subtracting a first modified version of said file from a second modified version thereof to obtain a difference; calculating a correlation between said difference and said second modified version; and comparing a value of said correlation with a threshold value to determine whether or not said invisible identifier is present in said second modified version. - View Dependent Claims (16)
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17. An invisible identifier irremovably embedded in an electronic file that contains at least one image, said identifier comprising:
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a smoothed, randomized black-and-white pattern; said pattern being rescaled to dimensions substantially the same as said file and overlaid thereon; said pattern being generated from a combination of a first and a second bit-string; said first bit-string being selected to represent authorship of said file; and said second bit-string being selected to represent content of said file. - View Dependent Claims (18, 19, 20)
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21. A computer-readable storage medium embodying program instructions for a method to mark, with an invisible identifier that cannot be removed therefrom, an electronic file containing a stream of samples comprising at least one image, said method comprising the steps of:
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selecting a first bit-string to represent authorship of said file; selecting a second bit-string to represent content of said file; combining said first and said second bit-string into said identifier; applying a function to convert said identifier into a number in a range effective for seeding a pseudo-random number generator; deriving a pseudo-random black and white pattern from said number by means of said generator, said pattern having dimensions substantially the same as said file; processing said pattern to create a random collection of connected areas, thereby transforming said pattern'"'"'s spectral energy to lower frequencies; smoothing said pattern; rescaling said smoothed pattern so that its amplitude is more than one unit sample; and adding said resealed, smoothed pattern to said file, whereby said file is marked with said identifier.
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22. A computer-readable storage medium embodying program instructions for a method to determine whether or not an electronic file containing at least one image also contains an invisible identifier, said method comprising the steps of:
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subtracting a first modified version of said file from a second modified version thereof to obtain a difference; calculating a correlation between said difference and said second modified version; and comparing a value of said correlation with a threshold value to determine whether or not said invisible identifier is present in said second modified version.
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Specification