Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

github.com

Post reply on HN
Print view View original

81–90 of 363 posts

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

#81

Post by copperx »

Matheus28 wrote: post #44
vermilingua wrote: post #37

The integrity of this entire system now relies on the security of the CSAM hash database, which has just dramatically increased in value to potential attackers. All it would take now, is for one CSAM hash to be known to the public, then uploading collided iPhone wallpapers to wallpaper download sites. That many false positives will overload whatever administrative capacity there is to review reports in a matter of da…

There's no need for someone to get the entire CSAM database. If they go on the darknet and just find enough images (or hashes) that would trip Apple's system, that would be enough. I'd assume any publicly available image on the darknet would likely also be on CSAM.

Exactly. It would be trivial for anyone to compile a list of possible known CSAM hashes. It would be illegal to do so, but only one person has to do it, and then the list of probably positive hashes can be distributed legally around the web.

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

#82

Post by iaw »

Really naive question. What's to stop apple from using two distinct and separate visual hashing algorithms? Wouldn't the collision likelihood decrease drastically in that scenario?

Again, really naive but it seems like if you have two distinct multi-dimensional hashes it would be much harder to solve the gradient descent problem.

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

#83

Post by shuckles »

onepunchedman wrote: post #76
shuckles wrote: post #73

Earlier quoted context omitted.

Why wait? Just send them the pictures on Facebook Messenger or Gmail or Dropbox today.

Nah that's so 2020, 2021 is all about low resolution legitimate porn being transformed to match CSAM. Get with the times!

Those will trip up 2020’s systems as well!

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

#84

Post by croutonwagon »

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?

Well according to reports that are generally the source of these collisions, the hashing code has been on the device since around December 2020 (14.3)

https://old.reddit.com/r/MachineLearning/comments/p6hsoh/p_a...

If Apple hasn't been honest about WHEN it was built into and added to their code base, why would anyone take their word for HOW its being used, or many of the other statements they are putting in their documents as of yet, at least until they are verified

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

#85

Post by heavyset_go »

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?

It doesn't necessarily mean that it will stop them from being a target, because Apple says this[1]:

> This program is ambitious, and protecting children is an important responsibility. These efforts will evolve and expand over time.

[1] https://www.apple.com/child-safety/

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

#86

Post by riffraff »

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.

But who would want that?

We all want privacy but it seems odd to try to DoS this, with high risk for yourself and very little to gain.

Might be useful when the system turns into mass political surveillance tho.

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

#87

Post by Dylan16807 »

ncw96 wrote: post #60
only_as_i_fall wrote: post #24

Earlier quoted context omitted.

Does it matter? Unless they're going to totally change the technology I don't see how they can do anything but buy time until it's reverse engineered. After all, the code runs locally. If Apple wants to defend this they should try to explain how the system will work even if generating adversarial images is trivial.

Apple has outlined[1] multiple levels of protection in place for this: 1. You have to reach a threshold of matches before your account is flagged. 2. Once the threshold is reached, the matched images are checked against a different perceptual hash algorithm on Apple servers. This means an adversarial image would have to trigger a collision on two distinct hashing algorithms. 3. If both hash algorithms show a match, t…

I do want to note that decrypting the low-res images would have to happen before step 2.

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

#88

Post by copperx »

ncw96 wrote: post #60
only_as_i_fall wrote: post #24

Earlier quoted context omitted.

Does it matter? Unless they're going to totally change the technology I don't see how they can do anything but buy time until it's reverse engineered. After all, the code runs locally. If Apple wants to defend this they should try to explain how the system will work even if generating adversarial images is trivial.

Apple has outlined[1] multiple levels of protection in place for this: 1. You have to reach a threshold of matches before your account is flagged. 2. Once the threshold is reached, the matched images are checked against a different perceptual hash algorithm on Apple servers. This means an adversarial image would have to trigger a collision on two distinct hashing algorithms. 3. If both hash algorithms show a match, t…

Will the high-resolution images be collected and used as evidence? Or just the visual derivatives? That's not clear.

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

#89

Post by onepunchedman »

copperx wrote: post #68
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…

It seems like I'm not going to sleep tonight. Sure, there is hyperbole in OP's comment (CSAM ransomware and automated law enforcement aren't a thing yet), but we're a few steps from that reality. Even worse, how long will it take until other cloud storage services such as Dropbox, Amazon S3, Google Drive et al implement the same features? Or worse, required by law to do so? This sounds like the start of an exodus fro…

Yeh I was talking in hyperbole, but the possible attack vectors this system enables are so powerful I felt it warranted. Under this system you are able to artificially ddos organizations that verify if CP is sent by sending legitimate, low-res porn whose hash has been modified. You can trigger legitimate investigations by sending CSAM through WhatsApp or through social engineering. You can also fuck with Apple by sending obvious spam.

* With regard to the legislative branch, they can even mandate changes to this system they aren't allowed to disclose. Once this system is in place, what is stopping governments from forcing other sets of hashes for matching.

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

#90

Post by heavyset_go »

robertoandred wrote: post #58
onepunchedman wrote: post #52

Earlier quoted context omitted.

I meant * could *. My point is that social engineering is a clear weak link in this system. They can also be sent regular photos whose hash matches the database, or use this repo to transform a regular pornographic photo's hash, making it hard for manual confirmation on Apple's part.

What kind of social engineering would lead an innocent person to save known CSAM to their photo library?

What kind of social engineering would lead an innocent person to install malware on their devices? Or do you think people like that want to take part in an illegal DDoS botnet?
Post reply on HN