You can’t trust your copier – German professor discovers that Xerox machines have been altering numbers on copies – perhaps for years!

This one still has me shaking my head in disbelief, but I’ve verified it.

The news is coming out of Germany and hasn’t broken big in the English speaking world yet, but it will.

Trust me on this – this is going to be a BIG story very soon.

Der Spiegel (the German equivalent of Time magazine) came out with the story today, but the real hero is German professor, D. Kriesel, at the University of Bonn. The story at Der Spiegel has not yet appeared in English. But, even better, here’s a link to the professor’s story (and blog) (in English) where I suspect things will be quickly developing.

To summarize, the good professor was working on some building plans which needed to be copied. He used a standard Xerox WorkCentre 7535 copier and suddenly noticed that some small numbers, placed in the center of each room giving the size of the room in square meters had been altered by the copier. Not just blurred, altered – swapped. A room which the original plans showed as 21.11 m2, showed up on the copy as 14.13 m2.

Again, the importance of this observation – The numbers were not just blurred, they were altered – swapped in fact for numbers taken elsewhere on the document.

Compare the images below:

-Original Building Plans- ——Xerox Copy——

Original Building Plans
Original Building Plans

Xerox copy
Xerox copy

 

Professor Kriesel has been able to reproduce the phenomenon on a number of documents and a number of copiers. Numbers set in small type, especially 7 points or less, seems most susceptible to being altered. The numbers are still quite readable by the human eye, and they are clearly altered.

Why is this happening?

Professor Kriesel’s hypothesis, which is being confirmed by lots of technical analysis, is that the Xerox copier is using an image compression algorithm that replaces tiles in the original with “similar”tiles found elsewhere in the document.

Professor Kriesel contacted Xerox, which at first seems to have dismissed his allegations as a joke.

They’re not laughing anymore as lots of other Xerox copier owners have been able to reproduce the behavior.

The implications are staggering.

What about document centers which have used Xerox copiers to produce digital images and then destroyed originals?

What implications are there for financial records? engineering documents? medical records?
How long has this behavior been going on? (hint: It has likely been happening undetected for years.)

Hacker News appears to have some of the liveliest early analysis.

Stay tuned – there will be lots more on this story over the coming weeks – a prediction by RedHatRob!

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