4 ms·

That image planting virus concept is the scariest thing. Could you trigger this system and get the police alerted with spam mms with images or spam email with i

by Rd6n6 5y ago

That image planting virus concept is the scariest thing. Could you trigger this system and get the police alerted with spam mms with images or spam email with images, or targeted ads that get the gray blob images into your tmp files? Or does it have to be an actual script downloading images, say, one per week in secret until it triggers?

robertoandred 5y ago
No, you couldn't. This is only checking images you upload to your iCloud photo library. Why would you save tons of gray blobs to your photo library? Why would gray blobs look like child porn? Why would Apple reviewers think gray blobs are child porn? Why would the NCMEC think gray blobs are child porn? Why would law enforcement spend time arresting someone for gray blobs?
- deleted 5y ago
  [deleted]
- nullc 5y ago
  The grey blob is a proof of concept. The existence of the original image is proof that not all images which produce the target hash are grey blobs. Since the grey blob exists, I believe it is fully possible to construct natural(-ish) images that have a selected hash. So, you should perhaps instead imagine attackers that modify lawful nude images to have matching hashes with child porn images. With that in mind, most of your questions are answered, except perhaps for "Why would the NCMEC think"-- and the answer would be "because its porn and the computer says its child porn". Of course, an attacker could just as well use REAL child porn. But there are logistic advantages in having to do less handling of unlawful material, and it's less likely that the target will notice. Imagine: if the target already has nude images on their host the attacker might use those as the templates. I doubt most people would notice if their nude image collection was replaced with noisier versions of the same stuff. And even if they did notice, "someone is trying to frame me for child porn" wouldn't be their first guess. :)
  - robertoandred 5y ago
    And where would they get the CSAM hash they need to match?
    - nullc 5y ago
      The bulk of the CSAM hash database comes widely circulated images, available on sleeze dark web websites (and historically on sketchy porn sites just on the web). So someone need only find a collection of likely included images and compute their hashes and publish it. The attack works just as well even if the attacker isn't sure that every hash is in the database, they just need to know enough likely-matches such that they get enough hits. Consider it this way, some attacker spends a couple hours searching for child porn and finds some stuff. ... what kind of failure would the NCMEC database be if it didn't include that material?
  - fouric 5y ago
    > Since the grey blob exists, I believe it is fully possible to construct natural(-ish) images that have a selected hash. At the very least, there are large classes of images that, while not realistic photographs, people will willingly download, that should be very easy to craft collisions for: Memes. In particular, given the distortions of surreal and deep-fried memes, it should be pretty easy to craft collisions there.
  - hannasanarion 5y ago
    The other thread demonstrates a similar attack with pictures of dogs. The same questions still apply. Why would you save tons of pictures of dogs to your photo library? Why would pictures of dogs look like child porn? Why would Apple reviewers think pictures of dogs are child porn? Why would the NCMEC think pictures of dogs are child porn? Why would law enforcement spend time arresting someone for pictures of dogs? What is the scenario where someone can be harmed reputationally or criminally because of a hash collision attack, where the same attack could not be performed more easily and causing more damage by actually using real CSAM images?
    - nullc 5y ago

by Rd6n6 5y ago

robertoandred 5y ago

No, you couldn't. This is only checking images you upload to your iCloud photo library. Why would you save tons of gray blobs to your photo library? Why would gray blobs look like child porn? Why would Apple reviewers think gray blobs are child porn? Why would the NCMEC think gray blobs are child porn? Why would law enforcement spend time arresting someone for gray blobs?

deleted 5y ago
[deleted]
nullc 5y ago
The grey blob is a proof of concept. The existence of the original image is proof that not all images which produce the target hash are grey blobs. Since the grey blob exists, I believe it is fully possible to construct natural(-ish) images that have a selected hash. So, you should perhaps instead imagine attackers that modify lawful nude images to have matching hashes with child porn images. With that in mind, most of your questions are answered, except perhaps for "Why would the NCMEC think"-- and the answer would be "because its porn and the computer says its child porn". Of course, an attacker could just as well use REAL child porn. But there are logistic advantages in having to do less handling of unlawful material, and it's less likely that the target will notice. Imagine: if the target already has nude images on their host the attacker might use those as the templates. I doubt most people would notice if their nude image collection was replaced with noisier versions of the same stuff. And even if they did notice, "someone is trying to frame me for child porn" wouldn't be their first guess. :)
- robertoandred 5y ago
  And where would they get the CSAM hash they need to match?
  - nullc 5y ago
    The bulk of the CSAM hash database comes widely circulated images, available on sleeze dark web websites (and historically on sketchy porn sites just on the web). So someone need only find a collection of likely included images and compute their hashes and publish it. The attack works just as well even if the attacker isn't sure that every hash is in the database, they just need to know enough likely-matches such that they get enough hits. Consider it this way, some attacker spends a couple hours searching for child porn and finds some stuff. ... what kind of failure would the NCMEC database be if it didn't include that material?
- fouric 5y ago
  > Since the grey blob exists, I believe it is fully possible to construct natural(-ish) images that have a selected hash. At the very least, there are large classes of images that, while not realistic photographs, people will willingly download, that should be very easy to craft collisions for: Memes. In particular, given the distortions of surreal and deep-fried memes, it should be pretty easy to craft collisions there.
- hannasanarion 5y ago
  The other thread demonstrates a similar attack with pictures of dogs. The same questions still apply. Why would you save tons of pictures of dogs to your photo library? Why would pictures of dogs look like child porn? Why would Apple reviewers think pictures of dogs are child porn? Why would the NCMEC think pictures of dogs are child porn? Why would law enforcement spend time arresting someone for pictures of dogs? What is the scenario where someone can be harmed reputationally or criminally because of a hash collision attack, where the same attack could not be performed more easily and causing more damage by actually using real CSAM images?
  - nullc 5y ago