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Hash collision in Apple NeuralHash model

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Re: Hash collision in Apple NeuralHash model

#161

Post by coldtea »

_jal wrote: post #153
coldtea wrote: post #135

Earlier quoted context omitted.

Accusations must be proven true, not untrue by the accused. And besides the "victim" in the latter case there was a whole lot of diplomatic pressure and political commotion to set him up, with carrots and sticks and the aid of friendly satellite states.

They must be proven true beyond a reasonable doubt to get a person in a funny robe to put them in jail. Normal humans are not required to prove anything in order to think them.

>Normal humans are not required to prove anything in order to think them.

No, but decent human beings are required to not think them true just because they're out there...

Re: Hash collision in Apple NeuralHash model

#162

Post by notRobot »

shapefrog wrote: post #122
icelancer wrote: post #59

Earlier quoted context omitted.

> Of course, grey noise will never pass for CSAM and will fail that step. Never? You sure that one or more human operators will never make this mistake, dooming someone's life / causing them immense pain?

I can guarantee nobody will see the inside of a courtroom, on charges of possession and distribution of child porn for possessing multiple images of grey noise (unless there is some steganography going on).

Many people never see the inside of a courtroom when false or unproven rape accusations are made against them, but their lives still get ruined because of the negative publicity.

Re: Hash collision in Apple NeuralHash model

#163

Post by Koffiepoeder »

magpi3 wrote: post #155
bo1024 wrote: post #152

Earlier quoted context omitted.

Not complete answers but background: apple’s system works by having your device create a hash of each image you have. The hash (a short hexadecimal string) is compared to a list of known CP image hashes, and if it matches, then your image is uploaded to Apple for further investigation. A devastating scenario for such a system is if an attacker knows how to look at a hash and generate some image that matches the hash,…

But how would the attacker get the generated image on a person's phone?

E.g. send them a whatsapp message that looks innocent

Re: Hash collision in Apple NeuralHash model

#164

Post by Majromax »

halflings wrote: post #8

Apple's scheme includes operators manually verifying a low-res version of each image matching CSAM databases before any intervention. Of course, grey noise will never pass for CSAM and will fail that step. The fact that you can randomly manipulate random noise until it matches the hash of an arbitrary image is not surprising. The real challenge is generating a real image that could be mistaken for CSAM at low res + i…

> The fact that you can randomly manipulate random noise until it matches the hash of an arbitrary image is not surprising.

It is, actually. Remember that hashes are supposed to be many-bit digests of the original; it should take O(2^256) work to find a message with a chosen 256-bit hash and O(2^128) work to find a "birthday attack" collision. Finding any collision at all with NeuralHash so soon after its release is very surprising, suggesting the algorithm is not very strong.

SHAttered is a big deal because it is a fully working attack model, but the writing was on the wall for SHA-1 after the collisions were found in reduced-round variations of the hash. Attacks against an algorithm only get better with time, never worse.

Moreover, the break of NeuralHash may be even stronger than the SHAttered attack. The latter modifies two documents to produce a collision, but the NeuralHash collision here may be a preimage attack. It's not clear if the attacker crafted both images to produce the collision or just the second one.

Re: Hash collision in Apple NeuralHash model

#165

Post by raxxorrax »

deadalus wrote: post #3

Expectation : Political rivals and enemies of powerful people will be taken out because c-ild pornography will be found in their phone. Pegasus can already monitor and exfiltrate every ounce of data right now, it won't be that hard to insert compromising images on the infected device. Any news about "c-ild porn" being found on someone's phone is suspect now. This has been done before : 1) https://www.deccanchronicle.…

That you felt the need to kill the 'h' in child is telling enough. Let's face it, security policy from the last 20 years was created by idiots. Plain borderline mentally inhibited idiots. All the surviellance introduced so much mistrust in some states that no terrorist could have ever dreamed of. There is no rational cost-benefit analysis, only propaganda about some Ivan being allegedly worse. Yes, great metric...

Sorry for the rant.

Re: Hash collision in Apple NeuralHash model

#166

Post by Ensorceled »

skhr0680 wrote: post #146
Ensorceled wrote: post #130

Earlier quoted context omitted.

> All criminal accusations, including true ones, should be treated as false until the accused is proven guilty. No, they need to be treated as unproven, a very critical difference. Just to be clear, witness testimony, including testimony FROM THE VICTIM, is evidence of the crime. Just for some reason, in rape cases, we go all wonky with this principle.

> including testimony FROM THE VICTIM, is evidence of the crime. Just for some reason, in rape cases, we go all wonky with this principle. In a criminal trial: Victim: This person did it Defendant: No I didn't Not guilty

That is not how it works, a large number of people are convicted on eye witness testimony from a single accuser.

Re: Hash collision in Apple NeuralHash model

#167

Post by Ensorceled »

ziml77 wrote: post #158
Ensorceled wrote: post #140

Earlier quoted context omitted.

Yes, rape is more difficult to prove than a number of other crimes. That is no reason to jump to a default "assume the accusation is false".

The reason to default to that is because a principle of our legal system is that people are innocent until proven guilty. On top of that proving someone guilty requires going beyond reasonable doubt.

The principle is the defendant is innocent until proven guilty, NOT that the accuser is making a false accusation.

There is a reason the verdict is "not guilty" instead of "innocent". After a not guilty verdict the legal system still does not assume the accuser was making a false accusation.

Re: Hash collision in Apple NeuralHash model

#168

Post by apetrovic »

reuben_scratton wrote: post #15
user-the-name wrote: post #9

Earlier quoted context omitted.

It can't. No actions are taken on hashes alone. The procedure is, if an account uploads some number of images with matching hashes, those images are verified by a human. This can attack that system itself, though, by overloading those humans with too much work looking at random noise, but that requires quite a large organised effort. It also requires getting a hold of actual blacklisted hashes, which I doubt anyone h…

"Verified by a human" - and that human will be an overworked, underpaid, overseas subcontractor who may well have an incentive to mash the "Confirm match" button from time to time to improve his performance.

I find it very hard to believe that Apple will put literal future of iPhone (just imagine the amount of bad press if one false negative comes out of review process and is reported to the authorities) to "overworked, underpaid overseas subcontractor".

Apple is greedy, ruthless, tone-deaf machine, but I don't think they're stupid.

Re: Hash collision in Apple NeuralHash model

#169

Post by deelowe »

Ensorceled wrote: post #140
Sebb767 wrote: post #137

Earlier quoted context omitted.

Testimony is seen as wonky in all kinds of cases. The problem with testimony about rape, however, is that, in those cases, supporting evidence is rarer than usual and even when it exists, proving it was non-consensual at the time is even harder (especially when relationships or affairs are involved).

Yes, rape is more difficult to prove than a number of other crimes. That is no reason to jump to a default "assume the accusation is false".

Depends. Are certain groups disproportionally more likely to benefit from said accusations?

Sorry, it needs to be said. It's easier to take one side of an argument when it's less likely to affect you personally.

Re: Hash collision in Apple NeuralHash model

#170

Post by [deleted] »

deadalus wrote: post #3

Expectation : Political rivals and enemies of powerful people will be taken out because c-ild pornography will be found in their phone. Pegasus can already monitor and exfiltrate every ounce of data right now, it won't be that hard to insert compromising images on the infected device. Any news about "c-ild porn" being found on someone's phone is suspect now. This has been done before : 1) https://www.deccanchronicle.…

[deleted]
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