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Comment by dsign | Hacker News Reader

So, these adversarial collisions are the images that I need to send to my enemies so that they go to prison when they upload those images to iCloud? It seems trivially easy to exploit.

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You can technically hide an adversarial collision inside a complete legit normal image. It won’t be seen by human eyes but it will trigger a detection. In addition, you can do the complete opposite by perturbing a CSAM to output complete different hash to circumvent the detection. All of these vulnerabilities are well known for perceptual hash.

So right there seems to be an issue to me. It seems like if you were trading in CSAM, you would run CLEANER -all on anything and everything. Because you know someone has already written that as proof of concept here.

You can also just send your enemies CSAM, it is more effective at imprisoning them.

They probably would not hold onto them and also now you have a paper trail of sending CSAM to people. But if you were to alter some innocent looking photos and send them to someone, they might store those.

Yes, but that won’t work since innocent looking photos won’t match the visual derivative.

That sounds like a good reason not to create a virtual SWATing vector then.

No. Because, as documented in the published material, hits are also reviewed by humans.

Downscaled derivative images are what are checked, and if the reviewer even suspects that the downscaled image contains sexual content of a minor, they're required to report it. At that point, it is the authorities who decide whether or not to continue to investigate and determine if the user possesses CSAM. That investigation alone can ruin lives.

The "downscaled" image 360x360. It's pretty easy to compare two images at that size to determine if they are the same. You're not going to end up investigated unless you actually have actual picture of child pornography. Also, not just one, the process doesn't even start until you have a fairly large number.

It's highly unlikely that the apple reviewer will have access to the actual image in the database, instead they will assess whether the blurry,b/w,etc modified thumbnail could possibly be illegal. Given the level of secrecy surrounding the contents of the DB, even the normal NCMEC reviewers may not have access to those for comparison. There are plenty of CG images, small legal models, or even images of erotic toys which could be used as the base image which would look very suspicious as a low quality thumbnail.

There will be someone along the line who will check that the image is, in fact, the actual listed image. Otherwise, there is no legal case to be made.

> There will be someone along the line who will check that the image is, in fact, the actual listed image.

That someone will be law enforcement, and they will get a warrant for all of your electronic devices in order to determine if you actually have CSAM or not. It's literally their job to investigate whether crimes were committed or not. Those investigations alone can ruin lives, even more so if arrests are made based on the tips or suspicions.

I wonder what scenarios are facilitated by sending adversarial collisions over simply sending over CSAM.

The images are sent for manual verification before you're turned in, so no.

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