With the advent of multimedia technology and the popularity of Internet communications, there has been great interest in using digital watermarks for the purpose of copy protection, content authentication, and data restoration. Digital watermarking technology allows the content owner to embed a secret signature, i.e., watermark, into the host content for many applications. For digital watermarking, a major challenge lies in the confident verification of the embedded watermark, even after the watermarked content undergoes various forms of unintentional or malicious modification.

Block diagrams of a typical watermark encoder and decoder, respectively:

Many watermarking algorithms have been proposed that are robust to signal processing applications and to lossy compressions, but they are vulnerable to geometric alterations. One method in which embedding is done in the Fourier-Mellin domain is resistant to geometric and scaling distortions. We are investigating new aspects related to watermarking in this domain.

Another application of digital watermarking uses an embedded watermark to help restore a degraded image. There are self-embedding watermarking schemes in which a highly compressed version of the work is embedded in the work. In blind restoration, the distortion that the cover work has undergone is estimated, and then these distortions are inverted. We are exploring new techniques for such applications.

Publications:

1. Dilijith Thodi and Jeffrey J. Rodriguez, "Expansion Embedding Techniques for Reversible Watermarking," IEEE Trans. on Image Processing, Vol. 16, no. 3, Mar. 2007, pp. 721-730. [ PDF ]
   
   
2. Diljith M. Thodi and Jeffrey J. Rodriguez, "Prediction-Error Based Reversible Watermarking," in Proc. 2004 IEEE Intl. Conf. on Image Processing, Oct. 24-27, 2004, Singapore, vol. 3, pp. 1549-1552. [ PDF ]
   
   
3. Diljith M. Thodi and Jeffrey J. Rodriguez, "Reversible Watermarking by Prediction Error Expansion," in Proc. 2004 IEEE Southwest Symp. on Image Analysis and Intepretation, Lake Tahoe, CA, March 28-30, 2004, pp. 21-25. [ PDF ]