There was a programming competition, can't remember which, similar to IOCCC but more about problematic software? where the redaction was reversible despite being pure black, due to the format chosen allowing for left over information in the image (vastly reduced quality but it was enough to allow text to be recovered!) [edit: see replies!]
There was also the Android (and iOS?) truncation issue where parts of the original image were preserved if the edited image took up less space. [edit: also see replies!]
Knowing some formats have such flaws (and I'm too lazy to learn which), I think the best option I think is to replace step 6 with "screenshot the redacted image", so in effect its a completely new image based on what the redacted image looks like, not on any potential intricacies of the format et al.
Maybe you're referring to "aCropalypse". Also there was an issue once where sections with overpainted solid black color still retained the information in the alpha channel.
I also recall at one point some image file format that ended up leaking sensitive info, because it had a embedded preview or compressed image, and the editing program failed to regenerate the preview after a censor attempt.
Was a loooong time ago, so I don’t remember the details.
AT&T leaked information, as did the US Attorney's Office, when they released PDFs with redacted information. To redact, they changed the background of the text to match the color of the text. You could still copy and paste the text block to reveal the original contents.
Wow, it took me a minute to figure out how his entry works. You really could read that code and assume it was correct. The resulting image is perfectly redacted visually, and the missing data is not appended or hidden elsewhere in the file. You would only discover it by inspecting the PPM image in a text editor. Very sneaky!
screenshot - im not convinced apple does not use invisible watermark to add info into image data. but for fact every photo you take with iphone, contains invisible watermark with your "phone serial number". to remove such watermarks, facebook is converting every picture you post for last 10 years... just weird extra con to using modern technology.
try to copy banknote on your printer, it will not print anything, just says error.
+ every page of text printed contains barely visible yellow marks containing again serial number of printer.
> can you even install MS-Paint anymore? Or is it Paint3D now?
Paint3D, the successor to MSPaint, is now discontinued in favor of MSPaint, which doesn't support 3d but it now has Microsoft account sign-in and AI image generation that runs locally on your Snapdragon laptop's NPU but still requires you to be signed in and connected to the internet to generate images. Hope that clears things up
> AI hasn't figured out a way to de-censor solid black yet.
I did though, under certain circumstances. Microsoft's Snipping Tool was vulnerable to the "acropalypse" vulnerability - which mostly affected the cropping functionality, but could plausibly affect images with blacked-out regions too, if the redacted region was a large enough fraction of the overall image.
The issue was that if your edited image had a smaller file size than the original, only the first portion of the file was overwritten, leaving "stale" data in the remainder, which could be used to reconstruct a portion of the unedited image.
To mitigate this in a more paranoid way (aside from just using software that isn't broken) you could re-screenshot your edited version.
It’s possible, depending upon the circumstances. If you are censoring a particular extract of text and it uses a proportional font, then only certain combinations of characters will fit in a given space. Most of those combinations will be gibberish, leaving few combinations – perhaps only one – that has both matching metrics and meaning.
What I love about this method is that it so closely matches what actual US govt censors do with documents pending release: take a copy, black it out with solid black ink, then _take a photocopy of that_ and use the photocopy for distribution.
This is similar to how I censor images on a cellphone. I use an editor to cover what I want to censor with a black spot, then take a screenshot of that edited image and delete the original.
Make sure your editor uses real pure black to cover the region. Chances are, if you use a general image editing app and if you deal with concepts like "brushes" you are not using pure black; it's mostly likely black with varying alpha channel.
News publications are also encouraged to do the same or even re-type the raw document. There was a story about how they shared raw scans of the leaked documents such that the yellow printer id dots were visible. That might have been for C. Manning?
Solid color would convey far less information, but it would still convey a minimum length of the secret text. If you can assume the font rendering parameters, this helps a ton.
As a simple scenario with monospace font rendering, say you know someone is censoring a Windows password that is (at most) 16 characters long. This significantly narrows the search space!
That sort of makes me wonder if the best form of censoring would be solid black shape, THEN passing it through some diffusion image generation step to infill the black square. It will be obvious that it's fake, but it'll make determining the "edges" of the censored area a lot harder. (Might also be a bit less distracting than a big black shape, for your actual non-advisarial viewers!)
I think the edges would still be evident, and this would just waste time and energy. I think a black square is just fine, so long as you can leak some information on the length of the secret. I would make it larger than it needs to be.
Back in the TechTV days one of the hosts used Photoshop to crop a photo of herself before posting it online. One would think a crop, completely removing the part of the image would be even better than solid black. However, with the way Photoshop worked in 2003, it didn't crop the embedded Exif thumbnail, which people were able to use to get the uncropped image.
Wow glad to see there were other fans of MSPaint, can't believe I built my open source version with wxWidgets 16 years ago https://github.com/murdockq/OpenPaint
This is odd because when I follow your steps up to Step 5, the rectangle that gets cut out from the screenshot is white. I did remember to follow steps 2 and 3.
this method looks worse than pixelation/blurry style, those "just" need to be updated to destroy info first instead of faithfully using the original text
If you REALLY care then replace the real information with fake information and pixelate that.
But most people don’t care enough.
Or I guess you could make a little video of pixelation that you just paste on top so it looks like you pixelated the thing but in reality there’s no correspondence between the original image and what’s on screen.
Testing that it doesn’t have text doesn’t help if the text was a bitmap in the first place.
Normally the use case is that you still want to distribute it as a PDF, usually consisting of many pages, and without loss of quality, so the printing/scanning/screenshotting option may not be very practical.
No, the real solution is to use an editor that allows you to remove text (and/or cut out bitmaps), before you add black rectangles for clarity.
1) Open screenshot in MS-Paint (can you even install MS-Paint anymore? Or is it Paint3D now?)
2) Select Color 1: Black
3) Select Color 2: Black
4) Use rectangular selection tool to select piece of text I want to censor.
5) Click the DEL key. The rectangle should now be solid black.
6) Save the screenshot.
As far as I know, AI hasn't figured out a way to de-censor solid black yet.