Method and apparatus for multi-bit zoned data hiding in printed images
AssigneeMassachusetts Institute of Technology
InventorsWalter Bender, Daniel Gruhl
Life of this patent
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Abstract
A technique for embedding a tracking number as a series of bits in a printed image alters characteristic parameter values at a set of pseudo-random locations chosen for each bit in an embedding zone. The alteration markedly changes the expectation value of some linear combination of mathematical functions of the values at that set of locations. A marker bit encoded to a higher certainty than other bits in the string aids in orienting the zones in decoding. The tracking number is detected and identified by exploiting the behavior of sums of a large number of random variables, based on the Patchtrack approach.
Claims18
A method of embedding information comprising a plurality of bits in a host image comprised of points, each point having a parameter value, the method comprising the steps of:
- a. defining a plurality of discrete zones within the image, each zone comprising a plurality of points;
- b. generating an ordered series of pseudo-random numbers for each bit to be embedded;
- c. assigning each pseudo-random number of each series to a first or a second group;
- d. for each series, within a single zone, associating each pseudo-random number with a point;
- e. designating each point associated with a pseudo-random number assigned to the first group to be a first point and designating each point associated with a pseudo-random number assigned to the second group to be a second point;
- and
- f. creating an altered host image by performing, within each zone, operations comprising:
- i. increasing the parameter value of at least some first points and of a first patch of points surrounding each of the at least some first points and
- ii. decreasing the parameter value of at least some second points and of a second patch of points surrounding each of the at least some second points, thereby embedding within the zone information comprising a bit for each series of pseudo-random numbers, such that the information embedded in all zones contains identical embedded information.
An apparatus for embedding information comprising a bit string in an image, the apparatus comprising:
- a. a computer memory for storing at least part of the image as an ordered set of pixels, each pixel having a pixel parameter value;
- b. means for defining a plurality of zones in the host image, each zone comprising a plurality of points;
- c. means for generating an ordered series of pseudo-random numbers for each bit to be embedded;
- d. means for assigning each pseudo-random number of each series to a first or a second group;
- e. means for associating, for each series, within a single zone, each pseudo-random number with a point;
- f. means for designating each point associated with a pseudo-random number assigned to the first group to be a first point and designating each point associated with a pseudo-random number assigned to the second group to be a second point;
- and
- g. means for creating an altered host image by performing, within each zone, operations comprising:
- i. increasing the parameter value of at least some first points and of a first patch of points surrounding each of the at least some first points and
- ii. decreasing the parameter value of at least some second points and of a second patch of points surrounding each of the at least some second points, thereby embedding within the zone information comprising a bit for each series of pseudo-random numbers, such that the information embedded in all zones contains identical embedded information.
Dependencies are inferred from the claim text.