Digital Watermarks Offer Added Security and Information

Clark School of Engineering faculty member Min Wu (top) is developing new technologies that will help safeguard electronic signatures.

New uses in information technologies by consumers--one example being the proliferation of digital signature pads for customers to electronically sign for retail purchases--have also expanded the need for greater security and anti-tampering measures.

Min Wu, an assistant professor of electrical and computer engineering, is currently refining areas of digital watermarking, developing algorithms that allow the digital embedding of a secondary "hidden" image, or watermark, within an original image or piece of line art. "This is a core technology that can be used in many applications," Wu says, explaining that in addition to verifying or annotating electronic signatures, digital watermarks have become a valuable tool for copyright protection in movies and music.

Wu's research is funded in part by a $350,000 CAREER award from the National Science Foundation and is a continuation of the work she began while earning a doctorate in electrical engineering from Princeton.

One particular challenge concerns data embedded in binary (two-color) images, a format typically used in electronic signatures. Until recently, watermarking data added to a binary image was fairly noticeable to the naked eye. While visually observing a watermark is okay in some instances, like the printed watermarks found on a new $20 bill, it is more problematic for electronic signatures on important business documents or letters of recommendation that need to look as authentic as possible.

Wu is working to perfect new algorithms for binary images that leave almost no visible traces, yet still allow for digital annotations and tamper-proof watermarks to be included. The digital annotation in the watermarking data can give customers peace of mind, Wu says, letting them know that their electronic signature is protected against potential misuse.

Also, Wu is working on new techniques to embed watermarking data within multiple curved lines in electronic documents--exactly the type of illustrative shapes that one would find on a digital map. "Digital watermarks are especially important for electronic maps that may contain classified material," she says. "Our technology allows you to determine if anyone has tampered with the document after its release, and allows you to trace exactly who it is that may have leaked the document from its authorized group of users."

Hopes of Inheriting Throne Shape Termite Evolution

Pictured are a group of normal soldier and worker termites of a primitive species known as dampwood termites or Zootermopsis nevadensis.

University of Maryland entomologists have discovered what may be a missing link in understanding Charles Darwin's theory of evolution. It's a story that would make Lady MacBeth feel right at home.

In developing his theory of the origins of species, one puzzle for Darwin was how some eusocial species such as termites, ants and bees--highly social creatures with only a few members that reproduce--fit into the scheme of natural selection. The celibate lives of most of the family members seem to fly in the face of evolution's drive for organisms to pass their genes to the next generation.

Studying Zootermopsis nevadensis, a primitive species of termite that lives on the West Coast, Maryland entomologists Barbara Thorne and Nancy Breisch have discovered that pitched battles may have launched the first termites onto their road to evolutionary success.

Like their ancestors, sets of reproductive kings and queens of this species move into trees that have been killed and softened by other invading insects, to set up housekeeping and churn out lots of little termites. Thorne and Breisch replicated the primitive termite real estate in their lab, running a tube to connect two evenly sized families, similar to pathways between neighbors in a tree in the wild. And then the fun began.

Within hours, the termites used the tube as an HOV lane to a neighboring colony. When two families met, battle ensued, usually ending with the death of one family's king and queen. The survivors followed the victors back to their homestead to form a single megacolony. The process repeated as the bigger colonies took over smaller families.

Thorne and Breisch think the less-than-neighborly competition in the primitive colonies is the key to how termites evolved successfully with only a few reproductive members.

"With termites, it appears that it is a family deal," says Thorne. "By staying with their family, offspring are protected, they have food, they help rear their siblings, and they have a chance to inherit the nest and colony if a parent is killed in battle. That's a bonanza payoff if it happens, whereas it's a big risk to leave the nest to try to start one's own colony."

Researchers Pioneer X-ray Navigation for Satellites

Image of the Crab Nebula taken by the Chandra X-ray Observatory.

Researchers in the Department of Aerospace Engineering have taken the idea of navigating by the stars more literally than most. Doctoral candidate Suneel Sheikh, together with Associate Professor Darryll Pines, have developed a system that uses X-ray radiation emitted by distant stars, called pulsars, for interstellar navigation. Pulsars, "the lighthouses of the galaxy" as Sheikh puts it, are unique in that they emit pulsed X-ray radiation at intervals as regular as most atomic clocks.

"A lot of people have said the system is like GPS, but that's not exactly true," says Sheikh. GPS, the Global Positioning System, uses a constellation of satellites, which emit time-coded position signals. A GPS receiver takes several of these signals and, using its own clock and the position information provided by each satellite, triangulates its position to within a few feet. Using X-rays for navigation presented a much greater challenge because the signals contain no time or position information.

To conquer the problem, researchers developed an algorithm based on a precise knowledge of the intervals at which each individual pulsar "pulses." Using X-ray detectors no larger than a breadbox, the technique compares when a pulsed signal is expected to arrive with when it actually does arrive. By computing the difference, the system can determine a spacecraft's position to within a kilometer--a resolution that researchers hope to improve in the near future. Similar to GPS, the X-ray system draws on signals from several pulsars to calculate an exact position in space.

In April the new X-ray system was named a 2003 Invention of the Year by the university's Office of Technology Commercialization. Sheikh envisions a broad market for the new system, primarily because it requires no intervention from Earth. According to Sheikh, "It's expensive to rely on ground operations to support the navigation of [satellites or other] spacecraft. With our system you can send satellites up and never have to deal with them again." Terrestrial uses are more problematic since the Earth's atmosphere absorbs most X-ray radiation. But Sheikh does envision the possibility of one day using the system for a purpose like driving a car ... on Mars.

Indonesian Rain Forest Disappearing Under Logging Onslaught

New findings indicate that large-scale logging is decimating the Indonesian rain forest, including supposedly "protected" areas. In a recent paper published in the journal Science, University of Maryland and Yale University researchers show that from 1985 to 2001, protected lowland forests in Indonesian Borneo declined by more than 56 percent (18,000 sq. miles). At this rate, all remaining non-industrial lowland forests in Kalimantan could be eliminated by 2011.

Borneo is the third largest island in the world. The two-thirds of the island that are part of the Republic of Indonesia are known as Kalimantan.

Continued forest clearance will harm Kalimantan's unique flora and fauna, including the Malayan sun bear, the bearded pig and the orangutan, the authors say. They note that this is the first study to use quantitative satellite- and field-based measures of deforestation and its causes, together with a geographical information system, or GIS, a tool that graphically displays sets, or layers, of information on a geographically accurate map.

"Failure to institute transparent and equitable land use solutions will lead to the irreversible ecological degradation of Borneo's terrestrial ecosystems," write Lisa Curran, Yale School of Forestry and Environmental Studies; Simon Trigg, Alice McDonald and Eric Kasischke, Department of Geography, University of Maryland; and Indonesian collaborators.

"Effective frontier governance and sound regional land-use planning are critical to maintaining even uninhabited and remote [protected areas] from regional, and increasingly international, market forces," they conclude.

This image shows the topography and distribution of logging within Gunung Palung National Park in Indonesian Borneo.

The park's remaining forest is shown in dark green while the red, orange and yellow regions are deforested and degraded areas. In the hilly areas where it is harder to conduct logging operations, much of the forest has been left relatively intact.

University of Maryland geographer Simon Trigg generated the picture by digitally superimposing an August 2002 Landsat 7 color composite image over a vertically exaggerated digital elevation model from the Shuttle Radar Topography Mission.

Landsat 7 is an earth-observing satellite that launched in 1999 under the guidance of a science team lead by University of Maryland geography professor Samuel Goward.

The Shuttle Radar Topography Mission was a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February 2000 and generated a high-resolution digital topographic database of Earth.

Study Shows Nanotubes Are Best Semiconductors

A team of researchers led by Michael Fuhrer, assistant professor of physics in the university's Center for Superconductivity Research, has fabricated a semiconducting nanotube transistor that conducts electricity better than any previous semiconducting material. The results provide new evidence that carbon nanotubes hold great promise for replacing conventional semiconductor materials in applications ranging from computer chips to biochemical sensors.

Computer-generated image of the structure of a carbon nanotube

In a December paper published in the online journal Nano Letters, Fuhrer and his team showed that their semiconducting carbon nanotube has a mobility almost 25 percent higher than any previous semiconducting material and more than 70 times higher than the mobility of the silicon used in today's computer chips. Mobility is a measure of how well a semiconductor conducts electricity.

"This is the first measurement of the intrinsic conduction properties of semiconducting

nanotubes," says Fuhrer, who heads the university's Nanoelectronics Research Group. "It is an important step forward in efforts to develop nanotubes into the building blocks of a new generation of smaller, more powerful electronics," says Fuhrer, whose work is supported by the National Science Foundation.

Carbon nanotubes--which can be thought of as a single-atom-thick sheet of graphite, rolled into a seamless cylinder--are being considered for many applications in electronic devices including transistors, memory cells, and chemical and biochemical sensors.

The International Technology Roadmap for Semiconductors, an assessment of the semiconductor industry's technology requirements, advises that a replacement material for silicon that has a higher mobility will be necessary by the year 2010. According to Fuhrer, the new findings by him and his colleagues indicate nanotubes could fill that role.

Last year, Fuhrer's group demonstrated that high-mobility semiconducting nanotube transistors could detect single electrons in a memory cell. This suggests that chemical sensors made from nanotubes could detect a single molecule of a target compound. --Lee Tune

Treat the Parents of ADHD Children, Too

Treatment for many young children with Attention Deficit/Hyperactivity Disorder, or ADHD, should also include treatment for their parents, according to new research from the University of Maryland's ADHD Program.

In one of the first systematic studies of pre-school children with ADHD, the research team found that parents of children with the condition are 24 times more likely to have the disorder themselves, as compared to the parents of children without ADHD. The study also showed that when ADHD preschoolers also suffer from other serious behavioral problems, the parents are two to five times more likely to suffer from a wide range of mental health problems, including depression, anxiety and drug addictions. Since treatments for children with ADHD rely heavily on parental support, parents' problems can interfere with a child's improvement.

"The evidence is dramatic and the message clear: we need to treat the whole family, not just the child," says University of Maryland psychologist Andrea Chronis, the study's lead author and director of the Maryland ADHD Program. "Too often the answer is just to give the children drugs. But our study suggests that when there are problems in the family, you need to address those too."

The study is the fourth in a 10-year project following the long-term progress of approximately 200 children recruited at the universities of Chicago and Pittsburgh. "We hope to identify meaningful early predictors of how these kids will do as they grow up."

Chronis and her team used rigorous psychological instruments to measure both the parents' and children's behavioral and mental health problems and ADHD symptoms.