6 ms·

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

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.

crossroadsguy 10mo ago
This is what I do while sharing such images. I crop out those parts first and then take another screenshot. I do not even risk painting over and then take another screenshot. I have been doing this forever.
userbinator 10mo ago
I'll just send an image and not bother with a PDF. (Note there's also other metadata in a PDF, which you may not want your recipient to know either.)
- PeterStuer 10mo ago
  There's also metadata in the image files. What specifically would be sensitive in the pdf with screenshots metadata that is also not present in the sceenshot image metadata?
  - userbinator 10mo ago
    PDF has something called an "info dictionary", which most mainstream PDF-writing software will fill out with various bits of info that you might not want known. Image files usually have substantially less metadata by default, unless it's one taken by a camera.
    - morshu9001 10mo ago
      Screenshots specifically tend to have very little metadata
agentifysh 10mo ago
it's absolutely bewildering how ridiculous everything has been so far in terms of competence and this really takes the cherry on the top near Christmas too. how much lower can they go ?!
- lostlogin 10mo ago
  The really interesting bit is whether they can go another term.
  - vanviegen 10mo ago
    They seem to be ahead of schedule abolishing a working democracy before the midterms.
- coldstartops 10mo ago
  Maybe it was always part of the plan. Plausible Deniability.
  - pjc50 10mo ago
    Good Soldier Svejk working at the FBI decided to follow an illegal order as badly as possible.
- yetihehe 10mo ago
  USA is still very high, so they can go much much lower, but I think they might go to some still lower places, finding them where we didn't even know such places could exist. Some ideas: - Leave NATO - Start openly supporting Russia and North Korea - Arrest whole International Criminal Court - Preventively invade China
  - baby 10mo ago
    I'm convinced slavery will be reintroduced before 2028
    - 10mo ago
reed1234 10mo ago
And even being this careful, if the opacity is slightly off it could be undone
ge96 10mo ago
The one that was crazy to me is undoing a blur effect (based on its algo), so yeah I also will layer and screenshot something
GistNoesis 10mo ago
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 https://github.com/unrealwill/jpguncrop )
- RamRodification 10mo ago
  I was thinking I understand what's going on but then I came to the image showing the diff and I don't understand at all how that diff can unredact anything.
  - OtherShrezzing 10mo ago
    It's not that you can unredact them from scratch (you could never get the blue circle back from this software). It's that you can tell which of the redacted images is which of the origin images. Investigative teams often find themselves in a situation where they have all four images, but need to work out which redacted files are which of the origins. Take for example, where headed paper is otherwise entirely redacted. So with this technique, you can definitively say "Redacted-file-A is definitely a redacted version of Origin-file-A". Super useful for identifying forgeries in a stack of otherwise legitimate files. Also good for for saying "the date on origin-file-B is 1993, and the file you've presented as evidence is provable as origin-file-b, so you definitely know of [whatever event] in 1993".
    - RamRodification 10mo ago
      Ok thanks. That sounds reasonable. >... and therefore you can unredact them from that readme is just not true then I guess?
      - user34283 10mo ago
        I mean, even the "crop" isn't used at all correctly, is it? I think the word should be "redact".
tetha 10mo ago
Personally, I only trust an image manipulation tool to put down solid colored blocks, or something that does not involve the source pixels when deciding on the redacted pixel. Formats like PDF are just so complicated to trust.
prameshbajra 10mo ago
I feel the same and do the same.
- amelius 10mo ago
  Me too.
9dev 10mo ago
In practical terms, a more convenient way to achieve this is just printing the document to a PDF, which rasterises the visible layer into what the printer would see. Most pdf tools support this.
- vanviegen 10mo ago
  That seems like a dangerous approach. Though printer drivers do often use rasterization, especially when targeting cheap printers, many printers can render vector graphics and text as well. Print-to-PDF will often use the later approach, unless of course the source program always rasterizes it's output when sending it out to the printer driver, or the used Print-to-PDF driver is particularly stupid.
- OneMorePerson 10mo ago
  You can, but I don't trust software for these types of niche but critical tasks hah. Next thing I know I'd be reading a headline about how "bug in print to PDF actually retains XYZ metadata"
TacticalCoder 10mo ago
I then convert the image to grayscale only. Then I apply a filter so that only 16 colors are used. And I then adjust brightness/contrast so that "white is really white". It's all scripted: "screenshot to PDF". One of my oldest shell script. 16 shades of grey (not 50) is plenty enough for text to still be smooth. I do it for several reasons, one of them being I often take manual notes on official documents (which infuriates my wife btw) but then sometimes I need to then scan the documents and send them (local IRS / notary / bank / whatever). So I'll just scan then I'll fill rectangle with white where I took handnotes. Another reason is when there's paper printed on two sides, at scan times sometimes if the paper is thin / ink is thick, the other side shall show. I wonder how that'd work vs adversarial inputs: never really thought about it.
- nubg 10mo ago
  care to share the script?
amelius 10mo ago
Maybe the person tasked with the redacting didn't agree so they chose the worst possible way to do it.
- noduerme 10mo ago
  Normally, I'd never attribute to intention what can be blamed on incompetence. Especially if the government is doing it. But sure, if I were the intern tasked with this job...
  - amelius 10mo ago
    > Especially if the government is doing it. Also if doing it right means more work?
    - noduerme 10mo ago
      My personal guess is that only 10% of people love their work, and don't object to doing more of it - governmental or private sector. But the efficacy of those people is amplified in the private sector and nullified in government. Source: I'm the guy everyone wanted on their group science project in high school, because I'd feel responsible for doing all the work while they smoked weed. I have brothers both in and out of government who work equally hard at similar jobs, and I see the dispatity of motivation.
jwrallie 10mo ago
I learned that a long time ago when I was a student and wanted to submit a pdf generated by a trial version of some software as an assignment and was trying to be clever and cover the watermark that said unregistered with a white box. When opening the file in my slow computer, I could see all the rendering of the watermark happening in slow motion until the white box would pop up on top of the text.
- tor825gl 10mo ago
  It's actually quite easy to open the pdf and see that there are several different elements per page to the document, eg the main text, an image, the footer, the title. Randomly removing these by trial and error will usually quite easily allow you to find the watermark and nix it, with the advantage that even a sophisticated recipient will not be able to find out from the pdf file what the watermark was.
- barrkel 10mo ago
  When I was a student, and using a shareware or trial version of some software and wanted some printed output from it without a watermark, I printed to postscript (chose a printer that supported postscript and the driver used it instead of rasterized images), but using a file instead of a printer. I could then open up the postscript, delete the commands that rendered the watermark, save it, then I converted it to PDF so it would be easy to print.
  - kccqzy 10mo ago
    You don't need PostScript for that. The PDF text commands are Tj and TJ, and rarely ' and ". They are easy to delete without going through PostScript. Tj means showing a simple text string. TJ means showing an array of strings possibly with space adjustments. ' means moving to the next line and showing a simple string. " means doing that and setting character spacing.
    - barrkel 10mo ago
      Perhaps, but it's easier to open up and edit a .ps file in a text editor than a PDF. PDF is a binary format with compressed streams, while postscript is just a stack-oriented programming language.

crossroadsguy 10mo ago

This is what I do while sharing such images. I crop out those parts first and then take another screenshot. I do not even risk painting over and then take another screenshot. I have been doing this forever.

userbinator 10mo ago

I'll just send an image and not bother with a PDF. (Note there's also other metadata in a PDF, which you may not want your recipient to know either.)

PeterStuer 10mo ago
There's also metadata in the image files. What specifically would be sensitive in the pdf with screenshots metadata that is also not present in the sceenshot image metadata?
- userbinator 10mo ago
  PDF has something called an "info dictionary", which most mainstream PDF-writing software will fill out with various bits of info that you might not want known. Image files usually have substantially less metadata by default, unless it's one taken by a camera.
  - morshu9001 10mo ago
    Screenshots specifically tend to have very little metadata

agentifysh 10mo ago

it's absolutely bewildering how ridiculous everything has been so far in terms of competence and this really takes the cherry on the top near Christmas too. how much lower can they go ?!

lostlogin 10mo ago
The really interesting bit is whether they can go another term.
- vanviegen 10mo ago
  They seem to be ahead of schedule abolishing a working democracy before the midterms.
coldstartops 10mo ago
Maybe it was always part of the plan. Plausible Deniability.
- pjc50 10mo ago
  Good Soldier Svejk working at the FBI decided to follow an illegal order as badly as possible.
yetihehe 10mo ago
USA is still very high, so they can go much much lower, but I think they might go to some still lower places, finding them where we didn't even know such places could exist. Some ideas: - Leave NATO - Start openly supporting Russia and North Korea - Arrest whole International Criminal Court - Preventively invade China
- baby 10mo ago
  I'm convinced slavery will be reintroduced before 2028
  - 10mo ago

reed1234 10mo ago

And even being this careful, if the opacity is slightly off it could be undone

ge96 10mo ago

The one that was crazy to me is undoing a blur effect (based on its algo), so yeah I also will layer and screenshot something

GistNoesis 10mo ago

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 https://github.com/unrealwill/jpguncrop )

RamRodification 10mo ago
I was thinking I understand what's going on but then I came to the image showing the diff and I don't understand at all how that diff can unredact anything.
- OtherShrezzing 10mo ago
  It's not that you can unredact them from scratch (you could never get the blue circle back from this software). It's that you can tell which of the redacted images is which of the origin images. Investigative teams often find themselves in a situation where they have all four images, but need to work out which redacted files are which of the origins. Take for example, where headed paper is otherwise entirely redacted. So with this technique, you can definitively say "Redacted-file-A is definitely a redacted version of Origin-file-A". Super useful for identifying forgeries in a stack of otherwise legitimate files. Also good for for saying "the date on origin-file-B is 1993, and the file you've presented as evidence is provable as origin-file-b, so you definitely know of [whatever event] in 1993".
  - RamRodification 10mo ago
    Ok thanks. That sounds reasonable. >... and therefore you can unredact them from that readme is just not true then I guess?
    - user34283 10mo ago
      I mean, even the "crop" isn't used at all correctly, is it? I think the word should be "redact".

tetha 10mo ago

Personally, I only trust an image manipulation tool to put down solid colored blocks, or something that does not involve the source pixels when deciding on the redacted pixel. Formats like PDF are just so complicated to trust.

prameshbajra 10mo ago

I feel the same and do the same.

amelius 10mo ago
Me too.

9dev 10mo ago

In practical terms, a more convenient way to achieve this is just printing the document to a PDF, which rasterises the visible layer into what the printer would see. Most pdf tools support this.

vanviegen 10mo ago
That seems like a dangerous approach. Though printer drivers do often use rasterization, especially when targeting cheap printers, many printers can render vector graphics and text as well. Print-to-PDF will often use the later approach, unless of course the source program always rasterizes it's output when sending it out to the printer driver, or the used Print-to-PDF driver is particularly stupid.
OneMorePerson 10mo ago
You can, but I don't trust software for these types of niche but critical tasks hah. Next thing I know I'd be reading a headline about how "bug in print to PDF actually retains XYZ metadata"

TacticalCoder 10mo ago

I then convert the image to grayscale only. Then I apply a filter so that only 16 colors are used. And I then adjust brightness/contrast so that "white is really white". It's all scripted: "screenshot to PDF". One of my oldest shell script. 16 shades of grey (not 50) is plenty enough for text to still be smooth. I do it for several reasons, one of them being I often take manual notes on official documents (which infuriates my wife btw) but then sometimes I need to then scan the documents and send them (local IRS / notary / bank / whatever). So I'll just scan then I'll fill rectangle with white where I took handnotes. Another reason is when there's paper printed on two sides, at scan times sometimes if the paper is thin / ink is thick, the other side shall show. I wonder how that'd work vs adversarial inputs: never really thought about it.

nubg 10mo ago
care to share the script?

amelius 10mo ago

Maybe the person tasked with the redacting didn't agree so they chose the worst possible way to do it.

noduerme 10mo ago
Normally, I'd never attribute to intention what can be blamed on incompetence. Especially if the government is doing it. But sure, if I were the intern tasked with this job...
- amelius 10mo ago
  > Especially if the government is doing it. Also if doing it right means more work?
  - noduerme 10mo ago
    My personal guess is that only 10% of people love their work, and don't object to doing more of it - governmental or private sector. But the efficacy of those people is amplified in the private sector and nullified in government. Source: I'm the guy everyone wanted on their group science project in high school, because I'd feel responsible for doing all the work while they smoked weed. I have brothers both in and out of government who work equally hard at similar jobs, and I see the dispatity of motivation.

jwrallie 10mo ago

I learned that a long time ago when I was a student and wanted to submit a pdf generated by a trial version of some software as an assignment and was trying to be clever and cover the watermark that said unregistered with a white box. When opening the file in my slow computer, I could see all the rendering of the watermark happening in slow motion until the white box would pop up on top of the text.

tor825gl 10mo ago
It's actually quite easy to open the pdf and see that there are several different elements per page to the document, eg the main text, an image, the footer, the title. Randomly removing these by trial and error will usually quite easily allow you to find the watermark and nix it, with the advantage that even a sophisticated recipient will not be able to find out from the pdf file what the watermark was.
barrkel 10mo ago
When I was a student, and using a shareware or trial version of some software and wanted some printed output from it without a watermark, I printed to postscript (chose a printer that supported postscript and the driver used it instead of rasterized images), but using a file instead of a printer. I could then open up the postscript, delete the commands that rendered the watermark, save it, then I converted it to PDF so it would be easy to print.
- kccqzy 10mo ago
  You don't need PostScript for that. The PDF text commands are Tj and TJ, and rarely ' and ". They are easy to delete without going through PostScript. Tj means showing a simple text string. TJ means showing an array of strings possibly with space adjustments. ' means moving to the next line and showing a simple string. " means doing that and setting character spacing.
  - barrkel 10mo ago
    Perhaps, but it's easier to open up and edit a .ps file in a text editor than a PDF. PDF is a binary format with compressed streams, while postscript is just a stack-oriented programming language.