> I didn't use any specialized software; it was just Mathematica with its built-in ImageDeconvolve function with guessed parameters for the Gaussian kernel.
is one of the most HN comments I've come across recently :)
>"Well, it should be obvious to even the most dimwitted individual, who holds an advanced degree in hyperbolic topology..."
Now show me the thread where Steve Jobs gave a shoutout to CmdrTaco :)
That gave me a laugh. I don't have any experience with Mathematica, but everytime I see it mentioned (usually on HN) I'm amazed at the sheer breadth the system is capable of. The amount of use cases and possibilities blows my mind.
Use ImageInstanceQ[image, object], where image is the image and object is "caprine animal". [0] [1]
[0] https://reference.wolfram.com/language/ref/ImageInstanceQ.ht...
[1] https://codegolf.stackexchange.com/questions/71631/upgoat-or...
On the one hand, it's perfectly built to spec and satisfied all requirements given by the customer.
On the other hand, you know it's incredibly fragile, and that the customer actually wants something different.
We had a similar issue in Australia as well.
Politicians phone bills are published on the government website in summary form.
Someone in 2017 decided to blank out their phone numbers by changing the phone number text colour to white (same as background).
End result - hundreds of politicians and former prime ministers had their phone numbers leaked.
https://www.abc.net.au/news/2017-03-20/phone-numbers-of-fede...
People used to be able to get the personal information of police officers if they were involved, intentionally or not, in a traffic accident with a police car. They would request for the traffic accident report, and that included the personal information (including home address) of the police officers in the car. I was in QA and I tested the change when it was fixed. It now includes the address of Police HQ when a police officer is involved in a traffic incident.
You can dictionary attack pixelated photos.
With Gaussian kernels, besides deconvolution you can sometimes also dictionary attack them if you have the original font and if the kernel is properly normalized kernel (i.e. most gaussian blurs).
Although I haven't tried, I think there may even be neural network based techniques that can perform even more effectively than a dictionary attack.
Separately, if the image editing tools added sufficient random noise to their mosaic filters they might be able to thwart most of these attacks, or at least make them significantly harder.
It's a total cheat but it is funny how close that can get you to something that might be actually useful.
[0]: https://pdfs.semanticscholar.org/20c2/b82eef0809df80a402f125...
Mind blown. Wow, that is very impressive.
You'd be surprised at how many times this happens on Government documents with redaction.
:S
Both MS Word and PDF have leaked redacted/removed information in the past. Wasting paper given the severity of some of these leaks is minimal cost.
With software you either need vetted and approved, very expensive software, or you have to accept a much higher error rate, because the operator cannot verify the results of the process with certainty.
An election doesn't need to be tamper-proof we just need to be able to detect tampering well enough to make tampering a loser's game.
The problem with randomly hand-counting a few boxes of ballots is that you then need to convince people that the random selection was uniform and fair and actually random.
There are methods to do that, but there are at least as complicated and full of cryptographic finesse, that they ain't simpler than vetting an electronic voting system in the first place.
Having said that: human counting isn't fool proof and is still open to abuse and tampering.
It's mainly that any village idiot can in-theory audit the human-run system, and that it would take a conspiracy with lots of people to engage in wide spread tampering.
The more people involved, the harder it is to prevent leaks.
What they can't trivially do with any system including paper ballots is remove ballots, compared to digital voting machines where you can add e.g. -100 votes to candidtate A, 100 votes to candidate B, thus ensuring that the total-votes field is correct while advantaging candidate B -- this was actually demonstrated by a security researcher on a Diebold touch-screen machine.
[0] https://www.atlasobscura.com/articles/pointing-and-calling-j...
https://www.theglobeandmail.com/canada/toronto/article-autom...
So, not only do you have the energy-investment thing noted in the/a sibling comment, you have the issue that there's no giant "THIS IS AN IMAGE" or "THIS HAS TEXT IN IT" that you can just Look At and know that yeah the document is okay. There's no lowest-common-denominator provability thing. You have to hyperspecifically know what to look for (render to image) then know how to verify whether it's an image or not.
And... how do you verify if it's an image? I don't have any PDF authoring/editing software on this machine, so the only thing I can think of is checking the Undo menu for "convert to image" or similar.
Under the hood, you created a new document, rasterize the original document page by page as JPEG, and insert the JPEGs back to the new document.
You can even create a fake "printer", that outputs a PDF with rasterized images as pages, so you don't have to teach the office clerks to anything extra.
To me, it seems to be indistinguishable from printing and scanning.
PS: It's pretty easy to verify if the page contains nothing but an image, programmically, especially if you also wrote the software that rasterize it in the first place.
It's pretty easy for a computer to verify any of this, the point is making it idiot proof. You don't have to be much of an idiot, if you process hundreds of documents a year where there's no way to visually verify the difference between a badly redacted document and a well redacted document, to screw up once. Especially when the difference between them is that you remembered to push the "redact correctly button", and if you forgot that, remembered to push the "verify if is redacted correctly programmatically" button before hitting send.
What you do is create a ritual where you have to walk across the room and use a physical machine. You'll remember doing that. And if you don't, since the output will look a bit crap, you can confirm it trivially.
Creating a process that has to be done perfectly every time or it fails catastrophically, and has few indications of failure during the process, is worse than having no process at all.
Document history was turned on and anyone who hit ctrl+z got the full class marks.
(The same lecturer initially failed me because they forgot to add my final exam score to my assignments score, and then took four months to fix it. They weren't very competent.)
Firstly because it's a nice mix of analog and digital, and secondly because it's short enough to fit in a tweet - yet extremely secure.
Ministry of Defence redaction policy, https://assets.publishing.service.gov.uk/government/uploads/...
I've seen people use image editors on mobile and they'll "scribble" out sensitive information, but one of the problems is that if you pick the wrong pen it'll blend your strokes so it's not 100% opacity (but on a casual glance it's close enough). You can zoom in and change the contrast of a photo that has been redacted this way and recover information.
Real life document workflows can be really tricky. What if one is required to print or photocopy the obscured document? Devastating for printer's toner or cartridge lifetime... In some cases opaque grayish rectangle does the job.
Which could result in thousands of dollars of loss over decades. Is that really a significant concern? Charge the client for it.
However, I agree that it requires some quick hand in image manipulation software.
That's the most surprising thing I've read today. I assumed it was destructive.
Eg knowing that the input was black text on white background or a natural image (instead of eg white noise) helps a lot.
Machine learning can also do a surprising good job of it, especially if you know what the target is (e.g. a face) https://www.vox.com/future-perfect/2019/9/4/20848008/ai-mach...
Sample code: https://gist.github.com/JonathanFly/80b669a72bf624d17b56a1cf...
Yes. Though that's just a corollary of doing better when you know something about the probability distribution of inputs.
(But a very useful and practical corollary. My formulation didn't give any hint how you might make use of that knowledge of the distribution.)
Black/delete (and flatten/rebroadcast) is the only way.
I have this at work, with engineering drawings. With mobile equipment often were not dealing with engineering companies per se, and they won't or don't know how to get us CAD models of their equipment. And we often don't have the equipment on have at the time we need to make drawings.
But if you have a PDF with vector drawings, often a manual, and one or two good dimensions you can make a reasonably accurate model. AutoCAD even makes this easy with the PDFIMPORT function.
More often than I would expect, there's a whole other drawing view either covered by a white box or off-page. Once it looked like it had been drawn over with a white paintbrush tool, and if course the path of that too was also visible.
There was a scandal around 2003 when a TV host took a topless photo, cropped it and shared the cropped photo online. Unfortunately, the software (Photoshop—I think CS3) she used to crop the photo stored the original photo as metadata if you didn't change the original filename. The original (uncropped) photo could be seen in the "Open File" preview dialog when opening the cropped version.
Not cutting it so that it becomes transparent since this may still preserve the color component of the RGBA-pixels, even if it is invisible and blended with a black background.
A friend of mine posted on Instagram a picture of a U.S. visa (or something similar; it was probably five years ago) to announce her trip to the U.S., and she took care to blur out sensitive information such as her passport number. But a Gaussian blur is easy to reverse and I successfully unblurred it and told her my discovery. I didn't use any specialized software; it was just Mathematica with its built-in ImageDeconvolve function with guessed parameters for the Gaussian kernel.
I personally recommend blacking out (add a black rectangle) instead of blurring, and if it is a PDF, convert to an image afterwards because too many PDF editors use non-destructive operations to add a new object instead of changing what's underneath.