Encryption method getting the picture

Eugen Leitl eugen at leitl.org
Thu Oct 24 03:19:04 PDT 2002


Encryption method getting the picture

By Sandeep Junnarkar
Staff Writer, CNET News.com
October 23, 2002, 9:06 AM PT

Researchers have created a new way to encrypt information in a digital 
image and extract it later without any distortion or loss of information.

A team of scientists from Xerox and the University of Rochester said that 
the technique, called reversible data hiding, could be used in situations 
that require proof that an image has not been altered.

Its uses could range from sensitive military and medical diagnostic images 
to legal documents and photographs of crime scenes. The technique could 
also be used to encode information within the image itself for cataloging 
and retrieving from databases.

Concerns about the authenticity of Web-based tickets, receipts and signed 
contracts have hampered the development of some e-commerce applications. 
While digital watermarking offers protection against tampering in most 
situations, it can also irreversibly change the quality of an image.

Current data-embedding techniques insert additional watermarking 
information, which inevitably distorts an image. While the distortion is 
small, it is usually irreversible. The new technique builds on previous 
methods but modifies the lowest levels of pixel values using 
data-embedding algorithms. It allows authorized viewers to extract the 
embedded authentication message while also removing any distortions 
created by the embedded information, the researchers said.

Although the technique is software-based, it could be implemented in 
hardware or in devices in which tightly controlling the image is critical, 
according the researchers.

For instance, a digital camera that carries the new algorithms could be 
used to gather forensic evidence for use later in a courtroom. Any 
subsequent manipulations of the pictures could be detected, and the area 
where they occurred could be pinpointed.

The technique was recently described in a research paper presented at the 
IEEE 2002 International Conference on Image Processing in Rochester, N.Y. 
It was co-developed by Mehmet U. Celik and A. Murat Tekalp of the 
University of Rochester and Gaurav Sharma and Eli Saber of Xerox.

The University of Rochester filed a patent application on the methods 
developed for reversible data hiding and plans to share the rights of the 
invention with Xerox.

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