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Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

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Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#201

Post by simondotau »

beachy wrote: post #195
simondotau wrote: post #164

Earlier quoted context omitted.

The fog of war is largely in the realm of post-puberty minors, photos of which are not being included in Apple's corpus of hashes. I find it difficult to believe that anyone could mistake or otherwise "fog of war" a photograph of an adult and a prepubescent minor. And that's assuming someone develops a hash collision which doesn't substantially mangle the photograph like the example offered on Github. Specifically, o…

I don't really want to do the research, so I'll take your word for it. But by fog of war I was thinking more like the victim already has some sleazy (though marginally legal) stuff on their computer, or a search led to a find of pot in their house, or they lied to try and get out of the rap, or perhaps the FBI offered them a deal and they took it because they saw no way out, or perhaps they were simply an unlikable i…

Even if I grant all of the above, I don't see how any of that is impacted by the distinction between on-cloud scanning and on-device scanning of photos which are being uploaded to the cloud.

Surveillance is surveillance. It's a bit more obnoxious that a CPU which I paid money for is being used to compute the hashes instead of some CPU in a server farm somewhere (which I indirectly paid for) but the outcome is the same. The risk of being SWAT-ed is the same.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#202

Post by simondotau »

Syonyk wrote: post #181
simondotau wrote: post #164

Earlier quoted context omitted.

The fog of war is largely in the realm of post-puberty minors, photos of which are not being included in Apple's corpus of hashes. I find it difficult to believe that anyone could mistake or otherwise "fog of war" a photograph of an adult and a prepubescent minor. And that's assuming someone develops a hash collision which doesn't substantially mangle the photograph like the example offered on Github. Specifically, o…

> Specifically, only images categorised as "A1" are being included in the hash set on iOS. Do we know that for sure? Apple has changed their mind enough times in the last week and a half that I'm convinced they're in full on defensive "wing it and say whatever will get people off our backs!" mode. You can't read the threat modeling PDF and conclude that it was run through the normal Apple document review process. It…

That document is over six years old. It has nothing to do with Apple.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#203

Post by copperx »

EGreg wrote: post #65
dannyw wrote: post #30

Earlier quoted context omitted.

The "send known CSAM" attack has existed for a while but never made sense. However, this technology enables a new class of attacks: "send legal porn, collided to match CSAM perceptual hashes". With the previous status quo: 1. The attacker faces charges of possessing and distributing child pornography 2. The victim may be investigated and charged with child pornography if LEO is somehow alerted (which requires work, a…

So, everyone is going to turn off their iCloud sync and they won’t be a target anymore?

Yes, until they add local scanning to macOS / iOS / iPad OS.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#204

Post by ehsankia »

sigmar wrote: post #151
fay59 wrote: post #123

Earlier quoted context omitted.

Before they make it to human review, photos in decrypted vouchers have to pass the CSAM match against a second classifier that Apple keeps to itself. Presumably, if it doesn’t match the same asset, it won’t be passed along. This is explained towards the end of the threat model document that Apple posted to its website. https://www.apple.com/child-safety/pdf/Security_Threat_Model...

What happens if someone leaks or guesses the weights on that "secret" classifier? The whole system is so ridiculous even before considering the amount of shenanigans the FBI could pull by putting in non-CSAM hashes.

Can't they just make a new one and recompute the 2nd secret hash on the whole data set fairly easily?

Also, the whole point is that it's fairly easy to create a fake image that collides with one hash, but doing it for 2 is exponentially harder. It's hard to see how you could have an image that collides with both hashes (of the same image mind you).

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#205

Post by simondotau »

Alupis wrote: post #198
simondotau wrote: post #196

Earlier quoted context omitted.

> It's it though? Yes. Your phone is your private property, just like your house or your car. Searching your private property requires a warrant or reasonable suspicion, otherwise it's a 4th Amendment violation. This twitter thread is worth a read. https://twitter.com/pwnallthethings/status/14248736290037022...

So, what does a person do if they do not consent to this search? Tough? You can't realistically avoid the iOS update. Apple has effectively given consent on your behalf... How will that fly?

If you do not consent to having your photos scanned for CSAM, turn off iCloud Photo Library. Same as how you opt out of CSAM scanning of your photo library on Android.

If you're concerned about other forms of scanning compelled by the Government, you never consented to the search. So even if Apple complied, the search is invalid and cannot be used to prosecute you.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#206

Post by copperx »

simondotau wrote: post #192
Syonyk wrote: post #179

Earlier quoted context omitted.

Attacks never get worse over time. It was quite literally less than 24h from "Oh, hey, I can collide this grey blob with a dog!" to "Hey, this thing that looks like cat hashes to the same thing as this dog!" You really think this is going to end at this proof of concept stage?

Of course it will get better. But it's not going to end at "Hey, this photograph of a sunset is visually unchanged" while now matching CSAM. That's just not plausible. It's not how these classifiers work. Regardless, this whole thing is moot because there are two classifiers, only one of which has been made public. Before any matches can make it to human review, photos in decrypted vouchers have to pass the CSAM matc…

Match the first classifier, and your file gets uploaded unencrypted to Apple. Which is fine if it's probable CSAM. But what if they switch efforts to combat, say, piracy?

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#207

Post by mukesh610 »

netr0ute wrote: post #72
robertoandred wrote: post #55

Earlier quoted context omitted.

The parent was proposing to “just send known CSAM”. But OK, say someone sends you a sunset that fools the hasher. Then what? Of course one match won’t do anything, so you’d need to download however many matching sunsets. Then what? The Apple reviewer would see they’re sunsets and you’d challenge the flag saying they’re sunsets. And if somehow NCMEC got involved, they’d see they’re just sunsets. And if law enforcement…

The point isn't to trick NCMEC, but rather create a DoS attack so no actual triggers can get through the noise.

As I've commented elsewhere, DoS can be easily mitigated by implementing another layer with basic object recognition to filter out false positive collisions.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#208

Post by Alupis »

simondotau wrote: post #205
Alupis wrote: post #198

Earlier quoted context omitted.

So, what does a person do if they do not consent to this search? Tough? You can't realistically avoid the iOS update. Apple has effectively given consent on your behalf... How will that fly?

If you do not consent to having your photos scanned for CSAM, turn off iCloud Photo Library. Same as how you opt out of CSAM scanning of your photo library on Android. If you're concerned about other forms of scanning compelled by the Government, you never consented to the search. So even if Apple complied, the search is invalid and cannot be used to prosecute you.

It does not appear one can opt out certain folders from this scan. If you enable iCloud backups, it's scans the entire shebang.

As previously mentioned, Android doesn't scan all photos on your device... Google scans content uploaded to their servers. Which is reasonable... It's their servers, they can host what they want. Your iPhone is your iPhone.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#209

Post by torstenvl »

simondotau wrote: post #205
Alupis wrote: post #198

Earlier quoted context omitted.

So, what does a person do if they do not consent to this search? Tough? You can't realistically avoid the iOS update. Apple has effectively given consent on your behalf... How will that fly?

If you do not consent to having your photos scanned for CSAM, turn off iCloud Photo Library. Same as how you opt out of CSAM scanning of your photo library on Android. If you're concerned about other forms of scanning compelled by the Government, you never consented to the search. So even if Apple complied, the search is invalid and cannot be used to prosecute you.

> If you're concerned about other forms of scanning, you didn't consent—so even if Apple complied, the search is invalid and cannot be used to prosecute you.

This is a dangerously false understanding of the law. Stop giving legal advice. You are not a lawyer.

Re: Show HN: Neural-hash-collider – Find target hash collisions for NeuralHash

#210

Post by gtm1260 »

Alupis wrote: post #35

So, what does Apple get out of all this, except negative attention, erosion of their image, possible privacy lawsuits, etc? I just don't understand what Apple's motivation would have been here. Surely this fallout could have been anticipated?

My guess is that internally, they've realized they have a big CP problem on iCloud. That's a huge liability.
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