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David Kriesel: Traue keinem Scan, den du nicht selbst gefälscht hast

media.ccc.de4 HN recommenders · 2019–2025
7M views · talk · evergreen · Uploaded 2015-01-01

David Kriesel's 31C3 talk, in German, on the discovery that Xerox scanner-copiers silently replace digits and letters in scanned documents. He explains how the bug stayed unnoticed in the wild for years.

Called a classic CCC talk, and the Xerox bug is cited as a cautionary tale about trusting scans and digitized archives.

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9 comments from Hacker News

@masswerk2019 · in “DARPA Is Building a $10M, Open-Source, Secure Voting System”

Thanks for the complementary links! Regarding Xerox scanner compression issues, compare this great CCC-talk by David Kriesel, "Traue keinem Scan, den du nicht selbst gefälscht hast" [0] – Sorry, German only. [0] [VIDEO] [1] [LINK] (Didn't MS's PDF-viewer have similar issues?)

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@snicksnak2020 · in “RC3 talk: How to survive in spacecraft [video]”

I would also highly recommend "Traue keinem Scan, den du nicht selbst gefälscht hast" [0] but I just noticed that there are no english subtitles available. [0] [VIDEO] (2015)

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@sdoering2021 · in “Contract by Email”

This reminded me of a great talk (in German) by David Kriesel about scanners not scanning correctly but replacing letters and numbers because of pattern matching (if I remember correctly). It was a really great talk. Not sure if there is an English version somewhere: [VIDEO]

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@a13692099932021 · in “Contract by Email”

> Not sure if there is an English version somewhere: [VIDEO] Seems to be: [LINK] Direct: [LINK] Which has german/english dual audio, but defaults to german (so presumably google ruined the english track on upload). If your video player doesn't support picking audio, you can probably fiddle with ffmpeg to strip out the german track.

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@solarkraft2021 · in “Confused Xerox copiers rewrite scanned documents, expert finds (2013)”

(2013). The whole ordeal lead to a quite legendary presentation by David at CCC (german, no captions, live translation available but pretty bad): [VIDEO] If you speak german and haven’t seen this yet, watch it, this is a classic. His talks are all entertaining and interesting.

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@winReInstall2022 · in “Archiving official documents as an act of radical journalism”

Related: [VIDEO] guy discovered that xerox workstations (like the ones to scan in government archives) corrupted numbers. Thus falsifying documents on a massive scale. Obamas "birth certificate" went through this document shredder. So distributing, non digital copies. Thats were the lasting value is.

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@masswerk2022 · in “Enhance Speech from Adobe – Free AI filter for cleaning up spoken audio”

Epic talk (in German, David Kriesel, "Traue keinem Scan, den du nicht selbst gefälscht hast"): [VIDEO]

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@Log_out_2023 · in “UK plan to digitise wills and destroy paper originals "insane" say experts”

Germany scanned its national archives in with xerox stations. We will never know what numbers might have been scrambled. [VIDEO] So similar projects existed and were so disastrous that they were quietly buried. To this day if a document was xerox scanned before the Bugfix it might be nil and void in court.

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@matrss2025 · in “iPhone 16 cameras vs. traditional digital cameras”

Worse, Xerox scanners specifically meant for digitizing documents have changed text for a long time. The compression algorithm they used (I think even in the default settings) sometimes replaced e.g. 6 with 8, and similar things. See: [VIDEO] (german, but there should be news articles from back then in english as well, somewhere)

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