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Comment by willis936 | Hacker News Reader

2 collisions out of a million images. I'm not sure how big the CSAM database is but if it's a tens of thousands and there are millions of photos uploaded a day then Apple could have a problem on their hands. This is all extrapolating from a study that doesn't use photos representative of what people actually upload. I would suspect when most photos being uploaded are of humans the actual collision rate will be much higher.

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This blogpost [1] by security researcher Sarah Jamie Lewis suggests that the false positive rate could be very high:

[1] https://pseudorandom.resistant.tech/obfuscated_apples.html

In their own testing they got 3 false positives out of 100 million.

They don’t take any action unless you have 30 matches in the database, which will not happen by chance.

I would agree if we assume that this very deterministic system behaved randomly.

It could happen on purpose if I intentionally send you 30 colliding images. I don’t know how iMessage handles images, but WhatsApp for example will put them directly into your photo library (and from there directly into iCloud if you’ve got syncing enabled).

Perhaps I could even do that without revealing my motives to you.

It would STILL just mildly inconvenience the Apple wageslave tasked with checking the notifications.

If you send actual CP, then that's a wholly different matter.

I mean, you could send them actual illegal content too.

And human reviewers are in the process. If you've got 30 matches and they are all pictures of bridges or whatever do you think the FBI is going to show up at your house?

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