Forensic experts track printer fingerprints

Researchers at Purdue University have developed image analysis techniques that may one day help tie counterfeit money and forged documents to the printers that produced them.

In lab experiments, the researchers examined documents that came from 12 different models of printers and were able to correctly link a document to its printer 11 times. The techniques currently let forensic investigators match a document with only a specific printer model, but will be honed so that a document can be matched to a particular printer.

"That means we will be able to tell the difference between counterfeit bills created on specific printers even if they are the same model," Edward Delp, professor of electrical and computer engineering at Purdue, said in a statement.

Delp and other professors and graduate students who worked on the project will present papers detailing the technology in November at the International Conference on Digital Printing Technologies in Salt Lake City. The group will also work with the U.S. Secret Service to develop new methods for tracing documents and counterfeit bills.

Software developed by Delp can identify "intrinsic signatures" of printers, or the subtle differences in the output of printers based on the small differences in their mechanics. To cut costs, printer manufacturers use plastic gears and other parts that create variations in printed sheets. These variations could be attenuated, but it would raise manufacturing prices considerably.

The group also exploits "banding," or the horizontal layers of ink that make up printed characters. Ink is laid down in horizontal lines or bands, which will vary in width and intensity because of the mechanical operation of the printer and the speed of the internal drum.

Banding, however, will change when the toner cartridge is changed. To counteract that effect, Purdue researchers are working with printer manufacturers to create a watermarking technology that would insert an "extrinsic signature" into the document. These signatures could not be recognized by the human eye but could be ferreted out through image analysis.

Jan Allebach, a professor of electrical and computer engineering, and George Chiu, a professor of mechanical engineering, have been working on a technology to reduce banding. The same technology can be used to insert the watermark.

[cpeterka]

Printer Fingerprints

1920's.. Gangsters put acid on their fingers to erase the finger prints.
2004's.. Go to Ebay, Get a $2000 color printer for $1000, Print out $10,000 worth of 20's and 50's and dump the printer in an Acid Tank that you buy with some of the counterfit money.
Priceless !!!

[Tex Murphy PI]

Yet another step towards Big Brother tech

I can understand how much a potential problem conterfieting is with a color inkjet - but to start watermarking everyone's printers to catch a small percentage of abusers is akin to treating everyone guilty of the crime with a broad brush stroke!

Serious counterfieters will NOT use such an obviously cheap and easily detectable method such as ink-jets to print out fake cash. And in the event they start doing so - I'm pretty sure that they would use a modified inkjet that removed the watermarks.

If the government is so keen on tracking everything people do, they might as well just chip everyone and watch them 24/7 - and get it over and done with right now, rather than impinging on the rights one bit at a time.