Xerox scanners/photocopiers randomly alter numbers in scanned documents
In this article I present in which way scanners / copiers of the Xerox WorkCentre Line randomly alter written numbers in pages that are scanned. This is not an OCR problem (as we switched off OCR on purpose), it is a lot worse – patches of the pixel data are randomly replaced in a very subtle and dangerous way: The scanned images look correct at first glance, even though numbers may actually be incorrect. Without a fuss, this may cause scenarios like:
- Incorrect invoices
- Construction plans with incorrect numbers (as will be shown later in the article) even though they look right
- Other incorrect construction plans, for example for bridges (danger of life may be the result!)
- Incorrect metering of medicine, even worse, I think.
To make things even more worse: The copiers in question are the common Xerox WorkCentres, and Xerox seemed to be unaware of the issue until we found out about it last Wednesday. Whats more, not only one different WorkCentre model seems to be affected, as we tested at least two with this issue (Xerox WorkCentre 7535 and 7556). Additionally, the current software release, as installed by xerox support, did not solve the issue, thus, the issue existed on the very old release we had installed, as well as on a very new one. The error has been confirmed by a xerox rental firm in the meantime, and Xerox is investigating as well, so it does not seem to be some dumb handling error or something similar (if I was thinking this, I of course would not publish it here).
As a result, 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? Did I even give them to others?
- What dangers are imposed by such possible document errors? Is there a danger of life for someone?
- Can I be sued for such errors?
Even though Xerox seems eager to solve the issue, because of the possible dangers an immediate publication of the issue is advisable. This is what I want to do with this article.
The rest of the article is organized as follows.
- By showing some real world examples I outline how we got aware of the issue, and how subtle it is. As it is hard to believe that scan copiers randomly alter written numbers, picture evidence is provided. (At first, I thought someone makes fun of my with this error, too).
- After that, I give some technical detail and describe the scan parameters set.
- Also, there will be a short manual how to reproduce this error.