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Multimedia Security And Forensics Authentication of Digital Images Sarah Summers Sarah Wahl CS525 Semester Project Spring 2006.

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Presentation on theme: "Multimedia Security And Forensics Authentication of Digital Images Sarah Summers Sarah Wahl CS525 Semester Project Spring 2006."— Presentation transcript:

1 Multimedia Security And Forensics Authentication of Digital Images Sarah Summers Sarah Wahl CS525 Semester Project Spring 2006

2 Motivation Seeing is believing … or is it?

3 Easy to be deceived

4 Goals  Identify image tampering methods.  Assess methods available for protecting images.  Assess image authentication techniques.  Identify directions for future work.

5 Categories of Image Tampering  There are three main categories of image tampering:  Enhancing  Compositing  Copy/Move

6 Enhancing  Changing the color of objects  Changing the weather conditions  Blurring out objects

7 Compositing Combining two or more images to create a new image

8 Copy-Move Copying regions of the original image and pasting into other areas. The yellow area has been copied and moved to conceal the truck.

9 What can be done to protect digital images?  Watermarking  Fragile watermarks  Semi-fragile watermarks  Self-embedding watermarks  Digital cameras with watermarking capabilities  Digital Fingerprinting/Signatures  Digital cameras with fingerprinting capabilities

10 Digital Watermarking  The basic concept of digital watermarking an image is that a low level signal is placed directly into the image data.  Any manipulation of the image will impact the watermark and subsequent retrieval of the watermark and examination of its condition will indicate if tampering has occurred.

11 Fragile Watermarks  Fragile watermarks are designed to detect every possible change in pixel values.  Variety of Techniques but in most cases, the watermark is embedded in the least significant bit (LSB) of the image.  Advantages: Pick up all image manipulations – malicious and non- malicious  Disadvantages: Too sensitive

12 Semi-Fragile Watermarks  They are robust, to a certain extent, and are less sensitive to pixel modifications.  Techniques:  Divide image into blocks and utilize bits from each block to calculate a spread spectrum noise like signal which is combined with DCT coefficients and inserted as a watermark.  Divide image into blocks, construct watermark in DCT domain from pseudo-random zero-mean unit variance Gaussian numbers, take the inverse DCT and insert into the image.  Advantage: less sensitive than fragile watermarks

13 Self-Embedding  Tampered images result in lost information. The previous techniques will only detect and localize areas of interest when authentication is carried out.  Self-embedding allows tamper detection and recovery of missing information.  General concept is that the image is embedded in itself in an encrypted form.  Advantage: Potential for original data to be retrieved.  Disadvantage: Tampering with the image can remove blocks of the original image making retrieval of content impossible

14 Digital Cameras with Watermarking Capabilities  Watermarking based on secret key, block ID and content. The image is divided into blocks and each block watermarked using a frequency based spread spectrum technique incorporating the secret key, block ID and block content.  Image of photographers iris is combined with the camera ID, the hash of the original image and other details specific to the camera.

15 Digital Fingerprints/Signatures  Based on the concept of public key encryption.  Hashed version of image is encrypted using a private key.  Encrypted file provides a unique signature/fingerprint of the image which can be used to authenticate by decryption with public key.  Mainly used in transmission of images.

16 Digital Cameras with Fingerprinting Capabilities  Epson Image Authentication System (IAS)  The IAS software in the camera instantly seals the captured images with an invisible digital fingerprint.  Verification of image is achieved by any PC with Image Authentication System software installed

17 Authentication Techniques  Active Authentication  Rely on the presence of a watermark or fingerprint.  Require knowledge original image  Algorithm/key used to embed the watermark or fingerprint.  Passive Authentication  No requirement of knowledge of original image.  Does not rely of presence of watermark or fingerprint.

18 Passive Authentication Techniques  Detecting Copy-Move  Detecting Traces of Re-sampling  Detecting Light Inconsistencies

19 Copy-Move Detection Original ImageTampered Image Exact MatchRobust Match

20 Copy-Move Detection Original Image Tampered Image PCA Detection

21 Re-sampling Detection Original ImageTampered Image Periodic pattern in Fourier Transform of altered region Fourier Transform of unaltered region

22 Inconsistencies in Lighting Genuine Image Tampered Image

23 Future Research  Development of a better self embedding technique.  Development of an all inclusive passive authentication technique.

24 Conclusions  Digital image forgeries can be used to deceive the public and the authorities.  They are here to stay.  Until non destructible/ non removal digital watermarks are perfected, passive authentication will remain necessary.  Currently no single passive authentication technique can detect all types of digital forgeries.

25 References  Hany Farid, Creating and Detecting Doctored and Virtual Images: Implications to The Child Pornography Prevention Act, Technical Report, TR2004-518, Dartmouth College, Computer Science.  Detection of Copy-Move Forgery in Digital Images, Jessica Fridrich, David Soukal and Jan Lukas, Proceedings of Digital Forensic Research Workshop, August 2003,  Detection of image alterations using semi-fragile watermarks, E.T. Lin, C. I. Podilchuk, and E.J. Delp,  Semi-fragile watermarking for Telltale Tamper Proofing and Authenticating, H. H. Ko and S. J. Park, Fragile%20Watermarking%20for%20Telltale%20Tamper%20Proofing%20and%20A. doc Fragile%20Watermarking%20for%20Telltale%20Tamper%20Proofing%20and%20A. doc Fragile%20Watermarking%20for%20Telltale%20Tamper%20Proofing%20and%20A. doc  Methods for Tamper Detection in Digital Images, Jiri Fridrich, Proc. ACM Workshop on Multimedia and Security, Orlando, FL, October 30-31, 1999, pp. 19-23,  Information Authentication for a Slippery New Age, S. Walton, Dr. Dobbs Journal, Vol. 20, No. 4, pp 18-26, Apr 1995  Blind Detection of Photomontage using Higher Order Statistics, T. Ng, S. Chang and Q. Sun,

26 References (continued)  A Digital Watermark, R. van Schyndel, A. Tirkel and C. Osborne, Proceedings of the IEEE International Conference on Image Processing, vol. 2, pp. 86-90, Austin, Texas, November 1994  A Watermark for Image Integrity and Ownership Verification, P. Wong, IS&T’s 1998 Image Processing, Image Quality, Image Capture, Systems Conference, Portland, Oregon, May 1998, pp. 374 – 379  An Invisible Watermarking Technique for Image Verification, M. Yeung and F. Mintzer, Proc. ICIP’97, Santa Barbara, California 1997  Image watermarking for tamper detection, Jiri Fridrich, Proc. ICIP '98, Chicago, Oct 1998,  Methods for Detecting Changes in Digital Images, J. Fridrich, Proc. of The 6th IEEE International Workshop on Intelligent Signal Processing and Communication Systems (ISPACS'98), Melbourne, Australia, 4-6 November 1998, pp. 173–177,  A Robust Content Based Digital Signature for Image Authentication, M. Schneider and S. Chang, Proceedings of the International Conference on Image Processing, 1996, Volume 3, Issue, 16-19 Sep 1996 Page(s):227 - 230

27 References (continued)  A New Fingerprinting Method for Digital Images, V. Fotopoulos and A. N. Skodras,  Mehdi Kharrazi, Husrev T. Sencar and Nasir Memon, Blind Source Camera Identification, International Conference on Image Processing, 2004, ICIP’04, Volume 1, 24-27 Oct. 2004, pp. 709 -712  Rotation, Scale and Translation Invariant Digital Image Watermarking, J.J.K. O’Ruanaidh and T. Pun, Proceedings of the ICIP, VOl. 1, pp 536-539, Santa Barbara, California, Oct 1997.  Secure Digital Camera, Paul Blythe and Jessica Fridrich,  Alin C. Popescu and Hany Farid, Exposing Digital Forgeries in Color Filter Array Interpolated Images, IEEE Transactions on Signal Processing, Vol. 53, Issue 10, Part 2, October 2005, pp 3948-3959  Epson's Image Authentication for digicams,  When is Seeing Believing, W. J. Mitchell, Scientific American, pp. 44 -49, February 1994.

28 References (continued)  Exposing digital forgeries by detecting inconsistencies in lighting by M. K. Johnson and H. Farid, ACM Multimedia and Security Workshop, New York, NY, 2005,  Exposing Digital Forgeries by Detecting Traces of Re-sampling, A. C. Popescu and H. Farid, IEEE Transactions on Signal Processing, 53(2):758-767, 2005,  Exposing digital forgeries by detecting duplicated image regions, A. C. Popescu and H. Farid, Technical Report 2004-515, Dartmouth College,  A Tutorial on Principal Components Analaysis, Lindsay I. Smith  Automatic Estimation of the Projected Light Source Direction, P. Nillius and j. –O. Eklundh, Proceddings of the IEEE Computer Science Conference on Computer Vision and Pattern Recognition, 2001  Protection of Digital Images Using Self Embedding, J. Fridrich and M. Goljan, Symposium on Content Security and Data Hiding in Digital Media, New Jersey Institute of Technology, May 14, 1999,  A Model for Image Splicing, T. Ng and S. Chang, ICIP '04. International Conference on Image Processing,. Volume 2, 24-27 Oct. 2004 Page(s):1169 - 1172 Vol.2

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