German researchers defeat printers' doc-tracking dots

Found on The register on Wednesday, 27 June 2018
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Beating the unique identifiers that printers can add to documents for security purposes is possible: you just need to add extra dots beyond those that security tools already add. The trick is knowing where to add them.

Anybody can take a scan of the document, and clear “empty” areas in an image editor, but the group's second technique is more sophisticated. After their algorithm identifies the pattern in use, it takes a mask of all possible dot locations in that pattern, and adds extra dots that conform to the layout, but render the code meaningless.

If you think about it, the idea is pretty simple but clearly very efficient.