Image Authentication Under Geometric Attacks

Vishal Monga, Divyanshu Vats, and Brian L. Evans
The University of Texas at Austin, Austin, TX 78712 USA

Download Version 0.1 (January 19, 2005)

Image Authentication Description with Examples

Image Hashing Research at UT Austin

Version 0.1 works under Matlab 6.5, and requires the image processing toolbox.

The parameters for affine transformation were set such that it works for 25 deg rotations. If you like to try out some other attacks or rotations there is one small change you would have to make.

In imageauth.m starting line 57 there are variables defined for the affine transformation matrix. Originally these are set to

i1 = 210:240;
i2 = 80:120;
i3 = -120:-80;
i4 = 210:240;

These suggest the range of values to look for in each entry of the affine transformation matrix. The code is set such that it makes only one pass through the set of transformations and thus it requires that the given values of i1,i2,i3,i4 are close to the actual transformation. So if you want it to work for 5 deg rotation, a good range of values will be

i1 = 150:200;
i2 = -200:-150;
i3 = 150:200;
i4 = 150:200;
Note that we are normalizing by 256 to get final values in the matrix. Accordingly you would have to set values for each attack that you define. It is possible to get an answer if you define all the i's from -256:256 but this will be computationally expensive and this case was avoided in the implementation.

I tried 5 deg with the above defined values and it seemed to work.

The code for end-stop wavelets is in gen_feature.m.

References to appropriate texts and published conference and journal articles are made in the MATLAB files wherever required

Dr. Vishal Monga completed this work while conducting his PhD research at The University of Texas at Austin. He is now with Xerox Labs, and can be reached at Prof. Brian L. Evans and Mr. Divyanshu Vats are currently with the department of Electrical and Computer Engineering at the University of Texas at Austin, TX - 78712.

For questions on this software toolbox, please write to