A bug in some Xerox multifunction printer models can lead to numbers being substituted for others in scanned pages, according to research published by a German computer scientist. The flaw could introduce errors on key documents such as invoices, he said.
The issue was discovered by David Kriesel, who detailed on his blog that some common WorkCentre and ColorQube multifunction printer models were randomly altering written numbers in scanned pages.
According to Kriesel, the issue is not due to errors with optical character recognition (OCR) algorithms, but, "is a lot worse – patches of the pixel data are randomly replaced in a very subtle and dangerous way," he wrote. "The scanned images look correct at first glance, even though numbers may actually be incorrect."
Analysis of the issue led Kriesel to identify a compression algorithm, JBIG2, as the cause of the problem. According to him, the algorithm was maintaining a dictionary of image patches, which it substitutes for portions of the scanned image, as long as the error generated by them is not "too high".
This was leading to situations where the number 6 is substituted for 8, for example, and vice versa, and only a close examination of the before and after documents would reveal the error.
"Anyone using those WorkCentres has to ask himself: how many incorrect documents (even though they look correct) did I produce during the last years by scanning with Xerox machines?" Kriesel wrote.
Fortunately, a fix for the issue appears to be to use scanning modes with the quality level set to "High" or "Higher". Only the "Normal" quality level uses JBIG2 compression, according to Xerox.
[UPDATE] In a statement sent to V3, Xerox said that the issue only exhibits itself if users switch from the factory standard default setting, and hence the vast majority of Xerox customers are unlikely to be affected.
However, Xerox said it is also developing a software patch that will disable the highest compression mode, completely eliminating the possibility of character substitution. The firm will begin rolling out the patch within a few weeks.
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