Comment by OneMorePerson
Comment by OneMorePerson 7 hours ago
It's funny seeing this play out because in my personal life anytime I'm sharing a sensitive document where someone needs to see part of it but I don't want them to see the rest that's not relevant, I'll first block out/redact the text I don't want them to see (covering it, using a redacting highlighter thing, etc.), and then I'll screenshot the page and make that image a PDF.
I always felt paranoid (without any real evidence, just a guess) that there would always be a chance that anything done in software could be reversed somehow.
If it's not done properly, and you happen at any point in the chain to put black blocks on a compressed image (and PDF do compress internal images), you are leaking some bits of information in the shadow casted by the compression algorithm : (Self-plug : https://github.com/unrealwill/jpguncrop )