> They have to come from the intersection of two databases from two jurisdictions.

My message directly answered that. A state actor can modify an apparent childporn image to match an arbitrarily hash and hand that image to other agencies who will dutifully include it in their database.

> Then you’d have to match _nearly exact photos_

It's unclear what you mean here. It's easy to construct completely different images that share a neuralhash. Apple also has no access to the original "child porn" (in quotes because it may not be), as it would be unlawful to provide it to them.

> but let’s be honest about the real risks

Yes. Lets be honest: Apple has made a decision to reprogram devices owned by their customers to act against their users best interest. They assure us that they will be taking steps to mitigate harm but have used powerful cryptography to conceal their actions and most of their supposed protections are unfalsifable. You're just supposed to explicitly take the word of a party that is already admittedly acting against your best interest. Finally, at best their protections are only moderate. Almost every computer security vulnerability could be dismissed as requiring an impossible series of coincidences, at yet attacks exist.

Even if a state actor constructs an image that is an NeuralHash collision for the material they wish to find, that only gets them through one of the three barriers Apple has erected between your device and the images being reported to a third party. They also need to cause 30 image matches in order to pass threshold secret sharing, and they need to pass human review of these 30 images.

Arguably investigation by NCMEC represents a fourth barrier, but I'll ignore that because it's beyond Apple's control.

> You just have to blindly trust that Apple

This has been true of all closed source operating systems since forever. Functionally, nothing has changed. And whatever you think of the decision Apple has made, you can't argue that they tried to do it in secret.

I pointed out above that the attacker could use legal pornography images selected to make it look like child porn. This isn't hard. Doing it 30 times is no particular challenge. I didn't use pornographic images in the examples I created out of good taste, not because it would be any harder.

[1] I've made a statement that I won't be posting any more preimages for now for that reason: https://github.com/AsuharietYgvar/AppleNeuralHash2ONNX/issue...

I have some residual nitpicks, on that point: many leaked data troves are much larger than that, though it is a material restriction.

The 30 threshold isn't leakless. Say you only have one hit, it still gets reported to Apple. The software also emits a small rate of "chaff", fake hits to help obscure the sub-threshold real hits. But it could still be used to produce a list of possible matches, including anyone with targeted material plus people who emitted fake matches, producing a list of potential targets much smaller than the whole population, for enhanced surveillance.

It would be interesting to know what the "chaff" rate is and whether any intelligence agency could stomach that amount of surveillance, particularly since it's by no means certain that any of them are real. In fact it seems to me that it's very unlikely indeed, especially if the material is in any way radioactive. After all, finding a match this way requires quite a few assumptions:

1. The target owns an iPhone;

2. The target has enabled iCloud Photo Library;

3. The target has a photo library small enough, or is paying for sufficient iCloud storage space, that the flagged images are included in the (sub)set stored in the cloud;

4. The target has imported the flagged images into their photo library rather than to iCloud Drive or any third party app like SpiderOak, Mega or Tresorit.

And that whatabout argument is supposed to justify the creation of a client-side scanning system that would massively lower the bar for abuse?

So third party auditors as well?

When it comes to keeping data private we face adversaries whos only rules seem to be what they can get away with. Against that, full transparency when it comes to the construction of our security infrastructure really needs to be the starting position.

What story are you referring to here?