This should be reason enough for you to not support the idea.
From day 1, it's matching legal images and phoning home about them. Increasing the scope of scanning is barely a slippery slope, they're already beyond the stated scope of the database.
My point is that we have no way to verify the database wouldn't be abused or mistaken and a lot of that rests on the fact that CSAM is not something people want to have to encounter, ever.
It's kind of like the PCAOB... private 501.3(c) with congressional oversight and funding.
I think the strategy is that the organization is able to do more for helping children internationally if they're not seen as part of the Justice department and the executive, which after the debacle with CBP and "kids in cages", was probably the right call.
Anyone should be able to scan their own library against the database for false positives. “But predators could do this too and then delete anything that matches!” some might say, but in a society founded on the presumption of innocence, that risk is a conscious trade-off we make.
The law requires companies like Google and Apple to report when they find CSAM and afiact they would generate hashes and add to this database if new material is found.
I don't know if there is any oversight in this. It's all done behind closed doors so you just have to trust that the people creating the hashes aren't doing anything nefarious or mistaken and that's a separate point apart from what others have said on here that you should be able to trust your devices you own to not be informants against you.
The thing I can publicly say is that the database is not strictly for illegal or even borderline imagery.
NCMEC try to keep the contents, processes and access to the database under wraps for obvious reasons.
By both a legal and moralistic standard they're not CSAM. Not even nearly.
Of course, this is a minority of the content in the database. But even 1 such image is gross neglect of stated purpose in my book.
Why would I have any content in my phone that would be in that database?
- A kitchen with nobody in frame.
- A couch with nobody in frame.
- Outdoor scenery with nobody in frame.
- A bathroom with nobody in frame.
Is it hard to believe you wouldn't download something like this without knowing where it came from?
I'm not talking about borderline stuff. I'm talking about content that has not even a hint of pornography or illegality.
Remember, these databases are essentially signature DB's, and there is no guarantee that all hashes are just doing a naive match on the entire file, or that all scans performedare fundamentally the same.
This is why I reject outright the legitimacy of any Client-based CSAM scanners. In a closed source environment, it's yet another blob, therefore an arbitrary code execution vector.
I'm sorry, but in my calculus, I'm not willing to buy into that, even for CSAM. It won't stay just filesystems. It won't stay just hash matching. The fact there's so much secrecy around ways and means implies there's likely dynamicity in what they are looking for, and with the permissions and sensors on a phone that many apps already ask for, my not one inch instincts are sadly firmly engaged with no signs of letting up.
I'm totally behind the fight. I'm not an idiot though, and I know what the road to hell is paved with. Law Enforcement and anti-CSAM agencies are cut a lot of slack, and enjoy a lot of unquestioning acceptance by the populace. In my book, this warrants more scrutiny, and caution not less. The rash of inconvenient people being rather frequently called out as having CSAM found on hard drives in media with no additional context indicates the CSAM definition is being wielded in a manner that produces a great degree of political convenience.
Again, more scrutiny, not less.
In principle, the OS environment could be made independently auditable - keeping undeleteable signed logs.
A person who creates CSAM likely doesn't just create CSAM all the time, right? Those innocuous pictures get lumped together with illegal content and make it into the database.
The database is a mess, basically. Of course it is. It's gigantic beyond your wildest estimates.
That’s not entirely true. If a police officer finds you in possession of a quantity of CP, especially of multiple different children, you’ll at least be brought in for questioning if not arrested/tried/convicted, whether the images were sexualized or not.
> nor would it ever end up in a database
That’s a bold blanket statement coming from someone who correctly argued that NCMEC’s database has issues (as in I know your previous claim is true because I’ve seen false positives for completely innocent images, both legally and morally). That said, with the amount of photos accidentally shared online (or hacked), to say that GP’s scenario can not ever end up in a database seems a bit off the mark. It’s very unlikely as sibling commenter said, but still possible.
That's why I said it's not inherently illegal. Of course, if you have a folder called "porn" that is full of naked children it modifies the context and therefore the classification. But, if it's in a folder called "Beach Holiday 2019", it's not illegal nor really morally a problem. I'm dramatically over-simplifying of course. "It depends" all the way down.
>That’s a bold blanket statement
You're right, I shouldn't have been so broad. It's possible but unlikely, especially if it's not shared on social media.
It reinforces my original point however, because I can easily see a case where there's a totally voluntary nudist family who posts to social media getting caught up in a damaging investigation because of this. If their pictures end up in the possession of unsavory people and gets lumped into NCMEC's database then it's entirely possible they get flagged dozens or hundreds of times and get referred to police. Edge case, but a family is still destroyed over it. Some wrongfully accused people have their names tarnished permanently.
This kind of policy will lead to innocent people getting dragged through the mud. For that reason alone, this is a bad idea.
With all due respect, please please stop making broad blanket statements like this. I'm far from a LEO/lawyer, yet I can think of at least a dozen ways a folder named that could be illegal and/or immoral.
> This kind of policy will lead to innocent people getting dragged through the mud. For that reason alone, this is a bad idea.
Completely agree.
It's very concerning if the fuzzy hash is too fuzzy, but I'm curious to know just how fuzzy it is.
So, it's theoretical, it's a different algorithm, and it's a case where someone is specifically trying to find collisions via machine learning. (Perhaps by "reversing" the hash back to something similar to the original content.)
The two above posters claim that they saw cases where there was a false positive match from the actual official CSAM hash algorithm on some benign files that happened to be on a hard drive; not something deliberately crafted to collide with any hashes.
I understand it seems like they don't want to give examples, perhaps due to professional or legal reasons, and I can respect that. But I also think that information is very important if they're trying to argue a side of the debate.
I gave that above in a sibling thread.
> I understand it seems like they don't want to give examples, perhaps due to professional or legal reasons, and I can respect that.
In my case, it’s been 7 years so I’m not confident enough of my memory to give a detail description of each false positive. All I can say is that the photos that were false positive that included people were either very obviously fully clothed and doing something normal, or the photo was of something completely innocuous all together (I seem to remember an example of the latter was the Windows XP green field stock desktop wallpaper, but I’m not positive on that).
Some of the false positives were of people, others weren’t. It’s not that the hashing function itself was problematic, but that the database of hashes had hashes which weren’t of CP content, as the chance of a collision was way lower than the false positive rate (my guess is it was “data entry” type mistakes by NCMEC, but I have no proof to back up that theory). I made it a point to never personally see any content which matched against NCMEC’s database until it was deemed “safe” as I didn’t want anything to do with it (both from a disgusted perspective and also from a legal risk perspective), but I had coworkers who had to investigate every match and I felt so bad for them.
In the case of PhotoDNA, the hash is conceptually similar to an MD5 or a SHA1 hash of the file. The difference between PhotoDNA and your normal hash functions is that it’s not an exact hash of the raw bytes, but rather more like the “visual representation” of the image. When we were doing the initial implementation / rollout (I think late 2013ish), I did a bunch of testing to see how much I could vary a test image and have the hash be the same as I was curious. Resizes or crops (unless drastic) would almost always come back within the fuzziness window we were using. Overlaying some text or a basic shape (like a frame) would also often match. I then used photoshop to tweak color/contrast/white balance/brightness/etc and that’s where it started getting hit or miss.
This has me pretty worried - once someone has been tarred with this particular brush, it sticks.
But image hashes are “perceptual” in the sense that the hash changes proportionally with the image. This is how reverse image searching works, and why it works so well.
It is claimed that the chance of being a false-positive for a positive match is one out of a trillion.
> Apple says this process is more privacy mindful than scanning files in the cloud as NeuralHash only searches for known and not new child abuse imagery. Apple said that there is a one in one trillion chance of a false positive.
https://techcrunch.com/2021/08/05/apple-icloud-photos-scanni...
I don't know what the cutoff is, but it doesn't sound like they believe that possession of a single photo in the database is inherently illegal. That doesn't mean this is overall a good idea. It simply weakens your specific argument about occasional false positives.