The United States of America, as Represented by the Director, National Security Agency

U.S. Government as Represented by the Director, National Security Agency

Government of the United States as Represented by Director National Security Agency

Sarah T Charlton

Katelyn J Meixner

Carla D Martin

Jeffrey B Farr

John A Emanuello

An improved method of determining a camera fingerprint and matching fingerprints is provided. A pixel-wise mass is defined and pixel positions having a low pixel-wise mass are identified. Once identified, the fingerprint values associated with those pixel positions are exchanged with statistically distributed random fingerprint values. Because the replacement values are statistically distributed, an improved fingerprint is provide resulting in improved accuracy of fingerprint matching.

Method for estimating an improved camera fingerprint by identifying low-mass pixel positions and correcting corresponding fingerprint values

A method is disclosed for using digital camera fingerprints to create bins of digital images generated by the same digital camera. The method includes determining, for each digital image in the set of digital images, a digital fingerprint. The method also includes sorting each digital image into one of a high-quality subset and a low-quality subset. The method also includes sorting each digital image in the high-quality subset into one of a plurality of bins. In each bin the images were determined, based on the digital fingerprints of the images in the bin, to have been generated by a single digital camera associated with the bin. The method also includes sorting each digital image in the low-quality subset into one of the plurality of bins, the sorting being performed based on the digital fingerprint of the digital image.

Binning digital images by source camera

The present invention discloses a method for comparing a camera fingerprint to a query fingerprint. An estimate of a camera fingerprint is obtained from a set of one or more images, and the query fingerprint is obtained from one or more images. Using these values, normalized cross-correlations values are determined for each possible alignment of the two fingerprints. Prior to calculating the noise floor, a set including the highest normalized cross-correlation values is identified. A universal noise floor is then calculated excluding this set from the noise floor calculation. The universal noise floor is utilized in calculating a correlation energy for each possible shift. The correlation energy values are then examined to determine whether the camera fingerprint and the query fingerprint match. A visualization tool may also be used to compare the camera fingerprint and the query fingerprint and determine whether the camera fingerprint and the query fingerprint match. The visualization tool may provide a plot utilizing surfaces or heat maps. The plots allow for a quick and easy analysis and determination as to whether the camera fingerprint and the query fingerprint match.

Method of comparing a camera fingerprint and a query fingerprint

A method of identifying a digital camera is disclosed. First and second digital images generated by the camera have dimensions that are not equal. The method includes calculating noise residuals and normalized cross-correlations (NCCs) between the noise residuals corresponding to candidate translations. The method further includes calculating a noise floor and identifying first and second peak values corresponding to translations. The method further includes calculating a peak ratio, determining that the peak ratio exceeds an alignment threshold and calculating a digital camera fingerprint for the digital camera based on the noise residuals and the first translation. The method further includes receiving a digital image, calculating a noise residual of the digital image, and determining that the image was generated by the digital camera based on the noise residual and the fingerprint and generating a record associating the image with the camera.

Growing community of inventors

Frederick, MD, United States of America

Sarah T Charlton