Machines have been altering numbers...
If you think your photocopier is producing exact duplicates of your documents, you might want to double-check — some popular Xerox scanners and photocopiers change text and numbers documents scanned and copied under the "normal" quality setting."According to a report from German computer scientist D. Kriesel, some Xerox copiers and scanners may alter numbers that appear in scanned documents. Having analysed the output of two such devices, the Xerox Copiers 7535 and 7556, Kriesel found that "patches of the pixel data are randomly replaced in a very subtle and dangerous way": in particular, some numbers appearing in a document may be replaced by other numbers when it is scanned."
In one example, David Kriesel who is based in Bonn, found copies he had made of construction plans had altered dimensions of some of the rooms. One Xerox printer had enlarged the square meter of a room from 14.13 m² to 17.42m², while another shrunk it from 21.11 m² to 14.13 m². Mr Kriesel found the copier would often change the number 6 into the number 8, and vice versa. He said the issue arose through an “image compression” fault, linked to how the scanners shrink the file size of scans.
Xerox aware of problem
Xerox said: “The problem stems from a combination of compression level and resolution setting. We do not normally see a character substitution issue... However, the defect may be seen at lower quality and resolution settings.”
