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Black bars alone may still leak info. First, if you add black bars on your own and don't use professional redaction features of software, you might miss the OC
by est31 6y ago
Black bars alone may still leak info.
First, if you add black bars on your own and don't use professional redaction features of software, you might miss the OCR text layer of the PDF, or the bar might be added as a separate object entirely which means it can also be removed later on.
Second, if you don't use monospace text, the width of the text you are redacting will reveal information about it. That's why monospace fonts are so commonly used in the intelligence community for example.
Third, if you just add a black bar to a screenshot, there might be residual values of the text left in adjacent seemingly white portions of the image, but they might not be entirely white due to compression effects. Better you run it through a filter before publishing.
- davchana 6y agoYes, in pdf, add bars, & then print it again as pdf, but as image.
- jbverschoor 6y agoEven black bars all leak the face that there’s something hidden
- davchana 6y agoDo you mean the typeface/font? If it is just a word we are hiding in a sentence/paragraph; it would be like fill in a blank task for reader; much more chance to guess from context. There, the leaking length will not matter.
- davchana 6y agoOh sorry, my bad, you mean fact, not face. Yes, I agree.
- jbverschoor 6y agoah. yeah fact :-)
- antegamisou 6y ago> First, if you add black bars on your own and don't use professional redaction features of software, you might miss the OCR text layer of the PDF, or the bar might be added as a separate object entirely which means it can also be removed later on. Looking at you, Preview on macOS.
- dragonwriter 6y ago> Second, if you don't use monospace text, the width of the text you are redacting will reveal information about it. If you do use monospace text, width reveals the exact redacted character count. If you don't use monospace text, it constrains the possible contents in a more complicated way, but it leaks information either way.
- spoonjim 6y agoIt leaks much less information when monospaced, although that information is easier to retrieve. Anyone can just visually inspect and see exactly how many monospaced characters were removed, but someone with the right tools and skills can narrow down the potential characters quite a bit if it's a short piece of non monospaced text.
- spoonjim 6y agoThis is why the real professionals use the same mechanism they always have: cut the offending text out of the paper with an x-Acto knife and make a photocopy.
- deleted 6y ago[deleted]
- Scoundreller 6y agoAlso helps prevent any issues related to double sided printing and bleedthrough.