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I'm really surprised to see a fellow HN poster making such a stark failure to generalize. You see that they can do this with pictures of dogs. What makes you

by nullc 5y ago

I'm really surprised to see a fellow HN poster making such a stark failure to generalize. You see that they can do this with pictures of dogs. What makes you think they can't do exactly the same with pictures of crotches? Presumably you don't believe there is some kind inherent dog-nature that makes dog images more likely to undermine the hash. :) People are using pictures of dogs because they are a tasteful safe-for-work example, not because anyone actually imagines using images of dogs. An actual attack would use ordinary nude images, probably ones selected so that if you were primed to expect child porn you'd believe it if you didn't spend a while studying the image. > where the same attack could not be performed more easily and causing more damage by actually using real CSAM images? Actual child porn images are more likely to get deleted by the target and/or reported by the target. The attacker also takes on some additional risk that their possession of the images is a strict liability crime. This means that if the planting party gets found with the real child porn they'll be in trouble vs with the hash-matching-legal-images they'll only be in trouble if they get caught planting it (and potentially only exposed to a civil lawsuit, rather than a felony, depending on how they were planting it). Personally, I agree that the second-preimage-images are not the most interesting attack! But they are a weakness that makes the system even more dangerous. We could debate how much more dangerous they make it.

hannasanarion 5y ago
What kind of non-child-porn imagery is so similar to child porn that it fools the NCMEC investigator who is looking at it side-by-side with its maliciously-collisioned hash match, but is at the same time so so dissimilar from real child porn that, as you say, the target won't report its sudden appearance on their device and the the sender won't be at legal risk? Your scenario requires the image (not the hash, but the regular human-perceptible image) to be both unremarkably innocent and incontrovertibly damning at the same time.
- nullc 5y ago
  You're assuming that there is a side-by-side comparison with a hash matching image. I think that is an extremely big assumption which assumes facts not in evidence at all. As far as what kind of image would be believed to be child porn without a side-by-side with the supposed match: ordinary porn. Without context plenty would be hard to distinguish, especially with the popularity of waxed smooth bodies and explicit close up shots. Prosecution over "child porn" that isn't is already a proved thing, with instances where the government was happily trotting out 'experts' to claim that the images were clearly a child based on physical characteristics only to be rebuffed by the actual actress taking the stand. ( https://www.crimeandfederalism.com/page/61/ https://www.crimeandfederalism.com/page/61/ )
  - hannasanarion 5y ago
    You still haven't explained how an image can be at the same time so benign that the user doesn't delete it from their phone and cloud service and the sender is in no legal danger, and yet so obviously pornographic that a jury will be convinced beyond any reasonable doubt that it's child porn. The entire point of this process is to catch only images from a known catalogue of existing images, of course there will be opportunity for side-by-side comparison. And if the side-by-side comparison can convince a jury that the images are the same, then the result is literally identical to if you had just sent the original image, the hash checking service hasn't impacted the attack whatsoever. The idea that new images of nudity could be caught in it is because of a mixup by the press after it was announced, because people confused it with a different parental control feature that detects nudity in images taken by your kids' phones. This is not the same thing.
    - nullc 5y ago
      I think I explained it adequately. An attacker gets some hashes likely to be in the database. The attacker modified legal pornography of young looking people, perhaps closeups of genitalia, to match the child porn hashes. There are plenty of examples of US persons being charged for lawful pornography which a prosecutor accused of being child porn, I linked to one such example-- where the accused was rescued only by the testimony of the actress, and where the prosecution had expert witnessess testifying that the images of an adult were images of a child. The attacker in this case would know the origin of the images and could point to them. The victim would have no idea where they came from. I have searched the case law, and can find no case where the NCMEC provided an image for comparison. Are you aware of any? You also seem to have continued to move the goalpost. Being merely accused of possessing child porn would be extremely damaging to a person. The fact that they might escape conviction by a jury after years of legal ordeal, incarceration, and having their reputation ruined, is not that much consolation. > The idea that new images of nudity could be caught in it is because This is an absurd claim. I have demonstrated (https://github.com/AsuharietYgvar/AppleNeuralHash2ONNX/issues/1#issuecomment-902977931 https://github.com/AsuharietYgvar/AppleNeuralHash2ONNX/issue...) that it is possible to alter existing images to match an arbitrary neuralhash resulting in a perfectly normal looking image. This point is not a matter for dispute, anymore. I could easily do so with a nude or pornographic image, I only chose to use SFW pictures out of good taste. My interest in apple's scheme arouse out of their malicious use of cryptography to shield their actions from accountability. I didn't even hear about the imessage nudie scanner until some time after. You can be certain no such confusion applies here.

by nullc 5y ago

hannasanarion 5y ago

What kind of non-child-porn imagery is so similar to child porn that it fools the NCMEC investigator who is looking at it side-by-side with its maliciously-collisioned hash match, but is at the same time so so dissimilar from real child porn that, as you say, the target won't report its sudden appearance on their device and the the sender won't be at legal risk? Your scenario requires the image (not the hash, but the regular human-perceptible image) to be both unremarkably innocent and incontrovertibly damning at the same time.

nullc 5y ago
You're assuming that there is a side-by-side comparison with a hash matching image. I think that is an extremely big assumption which assumes facts not in evidence at all. As far as what kind of image would be believed to be child porn without a side-by-side with the supposed match: ordinary porn. Without context plenty would be hard to distinguish, especially with the popularity of waxed smooth bodies and explicit close up shots. Prosecution over "child porn" that isn't is already a proved thing, with instances where the government was happily trotting out 'experts' to claim that the images were clearly a child based on physical characteristics only to be rebuffed by the actual actress taking the stand. ( https://www.crimeandfederalism.com/page/61/ https://www.crimeandfederalism.com/page/61/ )
- hannasanarion 5y ago
  You still haven't explained how an image can be at the same time so benign that the user doesn't delete it from their phone and cloud service and the sender is in no legal danger, and yet so obviously pornographic that a jury will be convinced beyond any reasonable doubt that it's child porn. The entire point of this process is to catch only images from a known catalogue of existing images, of course there will be opportunity for side-by-side comparison. And if the side-by-side comparison can convince a jury that the images are the same, then the result is literally identical to if you had just sent the original image, the hash checking service hasn't impacted the attack whatsoever. The idea that new images of nudity could be caught in it is because of a mixup by the press after it was announced, because people confused it with a different parental control feature that detects nudity in images taken by your kids' phones. This is not the same thing.
  - nullc 5y ago
    I think I explained it adequately. An attacker gets some hashes likely to be in the database. The attacker modified legal pornography of young looking people, perhaps closeups of genitalia, to match the child porn hashes. There are plenty of examples of US persons being charged for lawful pornography which a prosecutor accused of being child porn, I linked to one such example-- where the accused was rescued only by the testimony of the actress, and where the prosecution had expert witnessess testifying that the images of an adult were images of a child. The attacker in this case would know the origin of the images and could point to them. The victim would have no idea where they came from. I have searched the case law, and can find no case where the NCMEC provided an image for comparison. Are you aware of any? You also seem to have continued to move the goalpost. Being merely accused of possessing child porn would be extremely damaging to a person. The fact that they might escape conviction by a jury after years of legal ordeal, incarceration, and having their reputation ruined, is not that much consolation. > The idea that new images of nudity could be caught in it is because This is an absurd claim. I have demonstrated (https://github.com/AsuharietYgvar/AppleNeuralHash2ONNX/issues/1#issuecomment-902977931 https://github.com/AsuharietYgvar/AppleNeuralHash2ONNX/issue...) that it is possible to alter existing images to match an arbitrary neuralhash resulting in a perfectly normal looking image. This point is not a matter for dispute, anymore. I could easily do so with a nude or pornographic image, I only chose to use SFW pictures out of good taste. My interest in apple's scheme arouse out of their malicious use of cryptography to shield their actions from accountability. I didn't even hear about the imessage nudie scanner until some time after. You can be certain no such confusion applies here.