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Comment by filleokus | Hacker News Reader

In Sweden (and probably other places), a service called URKUND[0] ("deed" in Swedish) is used for automatic detection of plagiarism for school work.

I have always wondered to what extent they identify stuff like this, and other potential trickery with UTF-8 or removing text layers from PDF files.

0: http://www.urkund.com/en/

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Students in PL used invisible whitespace characters to avoid detection.

A neat trick would be to render the PDF into an image file, and then OCR that image file, and do the detection using the text file generated by the OCR process.

Just like VW's defeat device, the cheater would then need to create software that outputs something different when they see they are being rendered not to display, but to an image file...

So, one needs to use a font that OCR finds hard to avoid detection. Would rubbish keming do the trick, you could abide by imposed don't requirements but change kerning/leading?

At the point where you're doing this, it's better to reword the source. (It's what I did.)

You'd probably draw more attention to your paper if OCR fails to read it!

Presumably if you have the original file, you could reset the formatting to known-readable state before the OCR step.

Edit: You could also just use the text, but red-flag submissions where X% of the words used fall outside of the submitted language.

Would it not be easier to just have a lookup table which maps unicode points to visually equivalent glyphs?

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