Image Authentication Using Distributed Source Coding

Abstract

Image authentication is important in content delivery via untrusted intermediaries, such as peer-to-peer (P2P) file sharing. Many differently encoded versions of the original image might exist. On the other hand, intermediaries might tamper with the contents. Distinguishing the legitimate diversity of encodings from malicious manipulation is the challenge addressed in this talk.

In the first part of this talk, we propose a novel approach using distributed source coding for the image authentication problem. The key idea is to provide a Slepian-Wolf encoded quantized image projection as authentication data. This version can be correctly decoded only with the help of an authentic image as side information. Distributed source coding provides the desired robustness against legitimate encoding variations, while detecting illegitimate modification.

In the second part of the talk, we address the authentication of images which have undergone contrast, brightness, and affine warping adjustments. We propose the authentication decoder using an Expectation Maximization algorithm to learn the editing parameters while decoding the authentication data. Experimental results demonstrate that the proposed algorithm can distinguish legitimate encodings of authentic images from illegitimately modified versions, despite arbitrary contrast, brightness, and affine warping adjustment, using authentication data of less than 250 bytes per image.

Oral Defense

Date: Friday, October 2nd, 2009
Time: 9:30am (refreshments at 9:15am)
Location: CIS-X Auditorium [MAP]