Confused photocopiers randomly rewriting scanned documents

Photocopiers exist to produce close enough replicas of original documents. Traditionally, they just spit out the result onto paper. Most copiers these days can operate as (generally rather large) scanners, generating PDFs, TIFFs, or other electronic representations. But some Xerox copiers have recently been found to produce scans that, well, aren’t that close to the originals at all. The copiers are producing documents that look superficially similar to the originals but switch around numbers apparently at random.

German computer scientist David Kriesel wrote about the problem last week. He scanned some construction plans with a Xerox WorkCentre 7535 and noticed that the photocopier was resizing the rooms in his floorplans. One room annotated as being 21.11 square meters (roughly 277 square feet) got shrunk to 14.13 square meters (152 sq. ft.). So too did a room that should have been 17.42 square meters (187.5 sq. ft.). In both cases, the photocopier was taking the numbers from a third room—one that really should be 14.13 square meters—and using them for the other two rooms.

Further investigation revealed that this was not an isolated incident. A table of prices also came out wrong: a price of €65.40 ($ 86.71) became €85.40 ($ 113.22).

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