June 15, 1999 ORONO, Maine -- Computerized pictures may become a more commonly used way to transfer sensitive information as a result of research by a University of Maine professor and a Japanese colleague. Richard Eason of the Department of Electrical and Computer Engineering and Eiji Kawaguchi of the Kyushu Institute of Technology are seeking a patent for their work in the field of steganography.
The term literally means "covered writing." Methods of hiding information have been used for centuries. In ancient Greece, spies hid messages on wax covered boards that were normally used for writing. During World War II, German scientists created microdots that were the size of periods but large enough to contain photographs or other messages.
Today, computer images are as common as e-mail and offer sophisticated opportunities for hiding and transferring information. Such images can appear to us as familiar faces or attractive scenery, but to the computer, they are simply numbers. Eason and Kawaguchi have found a way to manipulate those numbers without distorting the image.
"Encryption technology is commonly used to transfer sensitive information," says Eason. "If you compare encryption to a locked safe in plain view, we're creating a safe which is hidden from view."
"What we're doing essentially is embedding data inside a picture. The picture that is presented to the viewer looks the same with or without the embedded data, and the file has not increased in size. We think of the picture as a 'vessel image' because it contains the additional data," says Eason.
To accomplish this slight of eye, Eason and Kawaguchi look for areas within pictures that are more complex than others, such as the leaves of a tree or a heavily patterned fabric. The computer sees such areas as complicated sets of binary numbers, and the engineers have found a way to identify how some of the numbers can be changed to accommodate new data.
Their work is based on pixels, the points of light which create images on computer screens. The color of a pixel is defined by binary digits, also called bits, but not all the bits for each pixel have equal rank. Some are more important than others in creating the picture on the screen. Eason's and Kawaguchi's technique does not change the most important bits. They still define the picture on the screen. However, their method does take advantage of the least important bits to accommodate the new data. Those least important bits can be changed without significantly altering the screen image.
If the image were like a movie, their technique would be akin to changing some of the extras in a crowd scene. The audience wouldn't notice differences in such minor players.
To see the embedded data, a viewer would need the software which created it in the first place. The software can also include a unique key which would be necessary to see the data in a given image, similar to encryption technology.
Eason is an expert in software programming and robotics. In previous research, his work with the Dexter Shoe Company led to a patent for a machine which trims soles for shoes. Eason and Kawaguchi have known each other since Eason's days in graduate school at the University of Tennessee. They have continued to correspond and collaborate on engineering projects, and they have arranged for their students to study on an exchange program in Japan and Maine.
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