3 ms·

Hashes might not fall under being "beyond reasonable doubt" - I'd be interested to see the legal history, if any, of them being used in convictions. There'll al

Hashes might not fall under being "beyond reasonable doubt" - I'd be interested to see the legal history, if any, of them being used in convictions. There'll always be the argument of the pigeonhole principle. On a similar note, I wonder if this will spur interest in a kind of file-doping program to confuse hashes of drive contents. A few pixels won't make a difference if you're planning on just viewing some images.

geofft 9y ago
I think they're also looking for other files, whose hashes they don't have forensic evidence of, to secure a stronger conviction (e.g., they might suspect him of producing child pornography and not just downloading it, and so they're looking for files whose hashes they don't already know).
kakarot 9y ago
I wonder if the same kind of error-tolerant fingerprinting used in technology like Shazam (recognizing songs from ambient recordings) could be generalized to combat such a doping program. You might have to do more than change a few pixels here and a unicode character or meta tag there. I even suspect things like color grading and, say, something like batching multiple images or text files together into one file, could be accounted for. Not to mention, such a doping program would preferably alter files in an imperceptible (aka, less mutated) fashion. I am a bit of an audiophile with my music and go to great lengths to rip high-quality, lossless, perfectly-encoded tracks for the sake of historical preservation. I imagine some pedophiles feel the same way about their data and the thought of tampering with the data's original state is abhorrent. Even a colorshift or one or two changed pixels might make it worthless in their eyes, much like a bad rip with barely perceptible clicks or an altered noise floor is worthless to me.
- shpx 9y ago
  https://en.wikipedia.org/wiki/PhotoDNA https://en.wikipedia.org/wiki/PhotoDNA They usually aren't using SHA (maybe they are in this specific case).
  - kakarot 9y ago
    Oh cool, I'd heard of PhotoDNA but I didn't know the details behind it. Thanks! "It works by converting the image to black and white, re-sizing it, breaking it into a grid, and looking at intensity gradients or edges." Pretty cool piece of technology. Seems like it covers the obvious bases. I imagine it also ignores meta tags as part of the hashing process, and operates directly on the pixel information. Perhaps one way to circumvent detection without making perceptual modifications (which would have to be somewhat significant to thwart the above method) could be a program that losslessly converts all of your images' pixel data to a generated file type only understandable by a program with a specific key in memory, which either directly displays the image or creates temporary files that could be used by a regular image viewer? The files could possibly be signed by more than one party for extra protection. I know it sounds just like encryption but I'm thinking of something a little different. Sort of a singular encrypted file that can be securely transferred to any file system. Sounds like a fun and challenging project but I'd hate for it to be so successful that it leads to child pornographers getting off the hook. "In December 2016, Facebook, Twitter, Google and Microsoft announced plans to use PhotoDNA to tackle extremist content such as terrorist recruitment videos or violent terrorist imagery." Dear lord, that is a stupendously slippery slope.
sjy 9y ago
Whether a person's guilt has been proven beyond reasonable doubt is a question of fact for the judge or jury deciding a particular case, and not something that can be determined by precedent. But given that people are regularly convicted of historical sex offences based solely on the credible testimony of the victim, it is difficult to imagine that a judge or jury would find a person not guilty of possessing a particular file solely on the basis of the pigeonhole principle.

geofft 9y ago

I think they're also looking for other files, whose hashes they don't have forensic evidence of, to secure a stronger conviction (e.g., they might suspect him of producing child pornography and not just downloading it, and so they're looking for files whose hashes they don't already know).

kakarot 9y ago

I wonder if the same kind of error-tolerant fingerprinting used in technology like Shazam (recognizing songs from ambient recordings) could be generalized to combat such a doping program. You might have to do more than change a few pixels here and a unicode character or meta tag there. I even suspect things like color grading and, say, something like batching multiple images or text files together into one file, could be accounted for. Not to mention, such a doping program would preferably alter files in an imperceptible (aka, less mutated) fashion. I am a bit of an audiophile with my music and go to great lengths to rip high-quality, lossless, perfectly-encoded tracks for the sake of historical preservation. I imagine some pedophiles feel the same way about their data and the thought of tampering with the data's original state is abhorrent. Even a colorshift or one or two changed pixels might make it worthless in their eyes, much like a bad rip with barely perceptible clicks or an altered noise floor is worthless to me.

shpx 9y ago
https://en.wikipedia.org/wiki/PhotoDNA https://en.wikipedia.org/wiki/PhotoDNA They usually aren't using SHA (maybe they are in this specific case).
- kakarot 9y ago
  Oh cool, I'd heard of PhotoDNA but I didn't know the details behind it. Thanks! "It works by converting the image to black and white, re-sizing it, breaking it into a grid, and looking at intensity gradients or edges." Pretty cool piece of technology. Seems like it covers the obvious bases. I imagine it also ignores meta tags as part of the hashing process, and operates directly on the pixel information. Perhaps one way to circumvent detection without making perceptual modifications (which would have to be somewhat significant to thwart the above method) could be a program that losslessly converts all of your images' pixel data to a generated file type only understandable by a program with a specific key in memory, which either directly displays the image or creates temporary files that could be used by a regular image viewer? The files could possibly be signed by more than one party for extra protection. I know it sounds just like encryption but I'm thinking of something a little different. Sort of a singular encrypted file that can be securely transferred to any file system. Sounds like a fun and challenging project but I'd hate for it to be so successful that it leads to child pornographers getting off the hook. "In December 2016, Facebook, Twitter, Google and Microsoft announced plans to use PhotoDNA to tackle extremist content such as terrorist recruitment videos or violent terrorist imagery." Dear lord, that is a stupendously slippery slope.

sjy 9y ago

Whether a person's guilt has been proven beyond reasonable doubt is a question of fact for the judge or jury deciding a particular case, and not something that can be determined by precedent. But given that people are regularly convicted of historical sex offences based solely on the credible testimony of the victim, it is difficult to imagine that a judge or jury would find a person not guilty of possessing a particular file solely on the basis of the pigeonhole principle.