Why blurring sensitive information is a bad idea (2007)
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Re: Why blurring sensitive information is a bad idea (2007)
#2A nice Gaussian blur would probably be fine, it's specifically the pixelation technique that's leaking data.
Re: Why blurring sensitive information is a bad idea (2007)
#3So if something is 1337 days old it gets autoreposted? Could live with that.
Previous discussion: https://news.ycombinator.com/item?id=1939607
A bit more precise this post is even older, and was first discussed in 2007 prominently in these two places: http://www.reddit.com/comments/xaae/how_to_extract_personal_...
https://www.schneier.com/blog/archives/2007/01/how_to_recove...
(please refrain from responding with XKCD references, I'm aware of that, just want to link to older discussions)
Re: Why blurring sensitive information is a bad idea (2007)
#4A nice Gaussian blur would probably be fine, it's specifically the pixelation technique that's leaking data.
Isn't that still forwardly deterministic i.e. you can apply the same algorithm to it but at a higher resolution?
Re: Why blurring sensitive information is a bad idea (2007)
#5A nice Gaussian blur would probably be fine, it's specifically the pixelation technique that's leaking data.
You think the technique mentioned in the article doesn't leak data? It actually leaks more data than a gaussian blur.
Gaussian blur suffers from exactly the same problem, although a different difference function is needed for it.
Re: Why blurring sensitive information is a bad idea (2007)
#6In some cases even blurring faces might be a bad idea. Just because we are unable to unblur a face today doesn't mean we are unable in 10 years or 100 years. In many cases this might not be a problem but in some cases this might lead to trouble later on which can be avoided just as easily.
Re: Why blurring sensitive information is a bad idea (2007)
#7A nice Gaussian blur would probably be fine, it's specifically the pixelation technique that's leaking data.
Isn't that still forwardly deterministic i.e. you can apply the same algorithm to it but at a higher resolution?
Yes it is reversible for practical purposes. There is some data loss on edges, which will manifest as noise on recovered image.
Re: Why blurring sensitive information is a bad idea (2007)
#8A nice Gaussian blur would probably be fine, it's specifically the pixelation technique that's leaking data.
Gaussian blur is a 100% reversible! You just sharpen using the same Gaussian settings for a Gaussian sharpen. It's only due to rounding to 8bit per colour that causes it to loose any information.
Re: Why blurring sensitive information is a bad idea (2007)
#9In some cases even blurring faces might be a bad idea. Just because we are unable to unblur a face today doesn't mean we are unable in 10 years or 100 years. In many cases this might not be a problem but in some cases this might lead to trouble later on which can be avoided just as easily.
You cannot unblur mosaic blurring. It's the equivalent of a hash. The best you can do is brute force possible input vectors. There will be many collisions. This technique only works because digits/numbers limit the input space for a credit card or bank number. For faces, the best you can do is validate if someone you already suspect or someone you have in a database, is the origin of the mosaic. If you had a picture of every person in your country, you could run them all through and find the origin - but you're not really unblurring as much as extracting information to do process of elimination on a 'image hash'
Re: Why blurring sensitive information is a bad idea (2007)
#10Their answer is to "color over it", but BE CAREFUL if you do that. I'm sure that some of us remember the US government document(s) in the late 90s/early 2000s that were released in redacted form, but the person didn't realize/understand that people with the Acrobat editor program could remove the black bars.