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Pet peeve: similar thing goes for QR-code redaction. People nearly always block out the middle part of the QR-code. However, actual information, the zigzag pat
by Phemist 3y ago
Pet peeve: similar thing goes for QR-code redaction. People nearly always block out the middle part of the QR-code.
However, actual information, the zigzag pattern, starts from the bottom-right. For many QR-code versions, the middle part encode _mostly_ ECC blocks, which are by definition redundant.
The fact that a QR-code doesn't decode in the regular scanning apps does not mean you cannot read any information from it.
- tgsovlerkhgsel 3y agoAlso, redacting text by blurring doesn't work well. If it's a screenshot (i.e. an exact representation, not something like a photo), you can usually try various combinations of characters and see what creates the same blurring pattern. If you know (or correctly guess) the exact parameters of the blur, this works far beyond what most people would consider recoverable by looking at it.
- schoen 3y agoI think I've seen both CTF levels and puzzlehunt puzzles based on partially obscuring a QR code, precisely so that it "doesn't decode in the regular scanning apps", and then challenging people to read it anyway.