Document "Fingerprints" Could Fight ID Fraud

John Roach
for National Geographic News

July 27, 2005

Office supplies have fingerprints, too, it seems.

A laser-based technology can read and record the unique "fingerprint" found in every piece of paper, cardboard, and plastic.

Scientists say the new tech offers an array of applications, from thwarting forged IDs and prescription drug packages to preventing identity theft and combating terrorism.

"For any strong security system what we need to know is, is the person really who they say they are and is the document … real?" said Russell Cowburn, a nanotechnology professor at Imperial College London.

New biometric security systems, such as iris scanners or hand scanners (which read signature vein patterns), can help suss out a person's true identity. But there are fewer ways to determine a document's authenticity.

"We are providing the missing link in the security chain," Cowburn said.

Document fingerprints arise from imperfections in the seemingly flat surfaces of paper, plastic, and similar materials. The flaws are evident at the microscopic level and are measured in microns and nanometers—scales approaching the size of molecules and atoms.

To read fingerprints at such small scales, the technology takes advantage of the optical phenomenon known as laser speckle.

"You shine a laser light onto any surface that is anything except perfectly flat. With even the smallest irregularities there is an imprint in the light that reflects off, an imprint of the irregularities," Cowburn explained.

The irregularities are different for every item. A digital recording of the irregularities serves as the fingerprint.

Cowburn and colleagues describe the application in tomorrow's issue of the science journal Nature.

Joshua Smith, now a principal investigator at Intel Research Seattle and an affiliate professor of electrical engineering at the University of Washington in Seattle, had previously developed a similar technology.

He found that imperfections in many materials can be read with ordinary cameras and proper lighting. Referring to the new application developed by UK scientists, Smith said that given the known properties of how laser speckle works, "it certainly makes sense that speckle could be used to read surface fingerprints."

Impossible to Copy

Cowburn, meanwhile, notes that document imprints illuminated by laser speckle are virtually impossible to copy with current technologies.

"Most traditional document-protection schemes work on the principle of 'Let's do something difficult for the bad guys to do.' The problem with that philosophy is the bad guys are clever and well resourced," Cowburn said.

"With this system, it's like, 'Let's do something impossible,'" he added. "Not even I know how to reproduce [these fingerprints]. All I can do is read them. So the task of the bad guy is then much, much harder."

The fingerprints are also resistant to rough handling.

For example, the fingerprints on a piece paper survived after the paper was scrunched into a ball, flattened, submerged in cold water, dried, and baked at 356° Fahrenheit (180° Celsius).

Quick and Efficient

According Cowburn, laser speckle allows researchers to record the identity of a document or piece of packaging quickly, efficiently, and cheaply.

To do so, a laser reader could be mounted at the end of a production line. As a product, such as an identification card or packaging for pharmaceuticals, goes by, the scanner could record the fingerprint and send it to a computer database.

The recording process can take as little as one thousandth of a second, Cowburn said. Once the fingerprint is electronically stored in a database, any suspect document or packaging could be checked for authenticity.

In the demonstration study described in Nature, the researchers recorded a 1.6-by-0.2-inch (40-by-5-millimeter) fingerprint of a piece of paper.

Although a smaller area is sufficient to get a fingerprint, Cowburn said that for security reasons "in most cases you're going to want to record a bigger area."

Smith, of Intel Research Seattle, cautioned that while document-fingerprinting technologies are an attractive way to prevent fraud, such systems require a standardized technology, which takes time and money to achieve.

For example, a label-making company would need to purchase and install the necessary equipment, such as computers and a scanning laser. "They're not going to do it unless someone has [the corresponding] readers out there." Smith said.

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