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Why blurring sensitive information is a bad idea (2007)

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Re: Why blurring sensitive information is a bad idea (2007)

#61

Post by chimeracoder »

frogpelt wrote: post #54
danepowell wrote: post #27

Earlier quoted context omitted.

He wasn't just a pedophile, he was a child molester.

"just a pedophile" A phrase I never thought I'd see.

A pedophile is someone who is sexually attracted to children, whether on not he/she acts on that desire in any way.

A child molester is someone who actually engages in inappropriate sexual activity with a child.

A child molester may or may not be a pedophile, for what it's worth (one may molest a child for reasons other than sexual attraction - even when you look at rape of adults, in many/most cases sexual attraction is not the primary motivation of the rapist[0]).

[0] https://en.wikipedia.org/wiki/Motivation_for_rape

Re: Why blurring sensitive information is a bad idea (2007)

#62

Post by bluedino »

robin_reala wrote: post #40
shinigami wrote: post #36

Earlier quoted context omitted.

Also, image formats like JPEG have a thumbnail stored in them, which may not be updated when you edit the image.

Do they? First I’ve heard of that…

There was a trend for a while of people posting images to imgur that had a totally different thumbnail. A rickroll of sorts.

Re: Why blurring sensitive information is a bad idea (2007)

#63

Post by cruise02 »

bryondowd wrote: post #52
userbinator wrote: post #38

Earlier quoted context omitted.

Actually, using fixed-width would be even easier since it reveals the length.

I'd be curious to see some numbers backing one or the other, but I suspect proportional would be better. Fixed width narrows to a number of characters. So it depends how many possible values have x characters. Proportional narrows to a particular width, which could be more granular than character count. So it depends how many possible values turn out to be exactly x pixels across given the type settings.

It doesn't really matter how many values turn out to be exactly x pixels across given the type settings, you still have to do an exhaustive search on different numbers of characters to find them. That problem is simplified by a fixed width font.

Re: Why blurring sensitive information is a bad idea (2007)

#64

Post by izzydata »

frogpelt wrote: post #54
danepowell wrote: post #27

Earlier quoted context omitted.

He wasn't just a pedophile, he was a child molester.

"just a pedophile" A phrase I never thought I'd see.

Someone who is homosexual isn't any more inclined to molest or rape someone of their own sex than a pedophile is to molest or rape a child.

More on topic about censoring important information. I'm not entirely sure about this, but I feel like I've seen images where the thumbnail was retained from a previous version. Even at 32x32 there might be some way to expand it and gather some kind of information from its pixelated form even after the actual image was censored.

Re: Why blurring sensitive information is a bad idea (2007)

#65

Post by tetrep »

ColinDabritz wrote: post #51
nathell wrote: post #30

In some cases, coloring over parts of the image might still not be enough. Specifically, when all of the following are true: (i) the domain of possible entries is reasonably small (e.g., a number or a name and surname), (ii) the text is printed in a proportional (not fixed-width) typeface, and (iii) enough of the rest of the line is visible to infer the font size and kerning settings.

I think this form of analysis is amazing. It breaks the "The best solution was to actually cut out the parts of the page you don't want seen and then scan in the result." approach from elsewhere in this thread as well. Even cutting out each portion of each line isn't enough because you can reconstruct line sizes. You could cut out each individual word and string them together, with a single size "redaction" block per…

>You could cut out each individual word and string them together, with a single size "redaction" block perhaps, but that's a lot of work.

Not really. OCR is plenty good enough to scan a document and then you can just replace anything you wanted redacted with a common string: [REDACTED]

Even if OCR wasn't an option, it would still (probably) be easier to type up the document than it would be to physically cut out all the things you want to redact.

Re: Why blurring sensitive information is a bad idea (2007)

#66

Post by tormeh »

Houshalter wrote: post #43
MichaelApproved wrote: post #31

Earlier quoted context omitted.

You don't have to go all the way back to the early 2000s to find poorly redacted federal documents. Rachel Maddow had a great segment on botched redactions, like removing the black lines from a PDF. The best solution was to actually cut out the parts of the page you don't want seen and then scan in the result. All other methods are prone to mistakes. Edit: corrected link to segment http://www.msnbc.com/rachel-maddow-…

Would a screenshot work?

Exactly my thought. A BMP is too simple to go wrong. There's so many pitfalls with digital files, because they can have much more information than the viewer will show you in an obvious manner or at all. Not only layers, but metadata (EXIF) and whatnot.

Re: Why blurring sensitive information is a bad idea (2007)

#67

Post by mokus »

cruise02 wrote: post #63
bryondowd wrote: post #52

Earlier quoted context omitted.

I'd be curious to see some numbers backing one or the other, but I suspect proportional would be better. Fixed width narrows to a number of characters. So it depends how many possible values have x characters. Proportional narrows to a particular width, which could be more granular than character count. So it depends how many possible values turn out to be exactly x pixels across given the type settings.

It doesn't really matter how many values turn out to be exactly x pixels across given the type settings, you still have to do an exhaustive search on different numbers of characters to find them. That problem is simplified by a fixed width font.

In general, though, a proportional face will give a larger number of possible widths, meaning more information to work with (fewer possible strings will map to any particular width).

Additionally, depending on the type of information you are trying to recover, you may already know the number of characters (for example, a US SSN), in which case fixed-width typefaces mean you get no information you didn't already have, whereas a proportional one would at least give you a little bit of info. But on the other hard I would also guess fixed-length strings such as an SSN are more likely to appear in a more "table"-like part of a document than in the middle of a paragraph of text.

I suspect it'd still be a bloody hard analysis either way, but at least according to this back-of-the-envelope theory a proportional typeface should preserve more information.

Re: Why blurring sensitive information is a bad idea (2007)

#68

Post by cruise02 »

mokus wrote: post #67
cruise02 wrote: post #63

Earlier quoted context omitted.

It doesn't really matter how many values turn out to be exactly x pixels across given the type settings, you still have to do an exhaustive search on different numbers of characters to find them. That problem is simplified by a fixed width font.

In general, though, a proportional face will give a larger number of possible widths, meaning more information to work with (fewer possible strings will map to any particular width). Additionally, depending on the type of information you are trying to recover, you may already know the number of characters (for example, a US SSN), in which case fixed-width typefaces mean you get no information you didn't already have,…

Oh yeah, in the case where you already know the number of characters, a proportional case font definitely gives you more information. That's a good point. I was thinking more of the general case where any number of characters might be redacted from a document.

Re: Why blurring sensitive information is a bad idea (2007)

#69

Post by im3w1l »

freehunter wrote: post #55
Houshalter wrote: post #43

Earlier quoted context omitted.

Would a screenshot work?

I've always drawn over sensitive parts in Paint or something, then taken a screenshot of it. It makes sure that everything is compressed to a single layer and can't be undone.

Just be sure to get all of it. It's pretty common that people leave a few pixels. How not to do it: https://imgur.com/ZaCIY5P

Re: Why blurring sensitive information is a bad idea (2007)

#70

Post by [deleted] »

izzydata wrote: post #64
frogpelt wrote: post #54

Earlier quoted context omitted.

"just a pedophile" A phrase I never thought I'd see.

Someone who is homosexual isn't any more inclined to molest or rape someone of their own sex than a pedophile is to molest or rape a child. More on topic about censoring important information. I'm not entirely sure about this, but I feel like I've seen images where the thumbnail was retained from a previous version. Even at 32x32 there might be some way to expand it and gather some kind of information from its pixela…

[deleted]
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