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Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

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Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#21
post #10
post #7

Earlier quoted context omitted.

What is the difference between CP and CSAM and why is everyone suddenly using the term CSAM instead of CP?

CSAM is not necessarily pornographic material, but merely material that becomes objectionable within context. For example, parents' photos of kids in the bath isn't CP. However _someone else_ having a _quantity_ of bath photos is CSAM, if they have no reasonable reason for possessing them.

[deleted]

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#22
post #20

Earlier quoted context omitted.

Last year Sam Harris interviewed Gabriel J.X. Dance, the deputy investigations editor at The New York Times [0]. They speak to this. It's a tough episode to listen to - they cover many uncomfortable topics along this theme. From what I recall of the episode, porn (rightly or wrongly) is seen as opt-in for the participants. But if children are involved it cannot be opt-in and is more appropriately described as rape or…

Depends on age and context doesn't it? Is a 17 year old snapchatting their private parts to her 17 year old boyfriend CSAM? Should both parties be imprisoned and go on sex offenders registries for life?

I'm not well versed enough in the topic (or the law) to have answers. I do think the podcast episode I pointed to does give a lot of food for thought. For me it was an eye opener, as a software engineer trying to build a beautiful future with strong beliefs around e2e encryption, etc.

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#23
(Context: I teach computer security at Princeton and have a paper at this week's Usenix Security Symposium describing and analyzing a protocol that is similar to Apple's: https://www.usenix.org/conference/usenixsecurity21/presentat....)

The proposed attack on Apple's protocol doesn't work. The user's device adds randomness when generating an outer encryption key for the voucher. Even if an adversary obtains both the hash set and the blinding key, they're just in the same position as Apple—only able to decrypt if there's a hash match. The paper could do a better job explaining how the ECC blinding scheme works.

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#24
Why does Apple even bother with encryption? They should just skip all of the warrant requirements etc and use their iCloud keys to unlock our content and store it unencrypted at rest.

Maybe they can also build an api so that governments can search easily for dissidents without the delays that the due process of law causes.

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#25

Why does Apple even bother with encryption? They should just skip all of the warrant requirements etc and use their iCloud keys to unlock our content and store it unencrypted at rest. Maybe they can also build an api so that governments can search easily for dissidents without the delays that the due process of law causes.

Facetious as this is, I can't imagine this is anything other than Apple's endgame here.

The best of both worlds: keep advertising their privacy chops to the masses, while also allowing any and every government agency a programmatic way to hash-verify the data passing through their systems in real-time.

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#26
Regardless of whether this attack works or not, you'd assume this scheme produces a wider attack surface against pictures in iCloud and against iCloud users. One attack I could imagine is a hacker uploading child porn to a hacked device to trigger immediate enforcement against a user (and sure, maybe there are more controls involved but would you carry around a very well-protected, well-designed hand grenade in your wallet just so you're bad, it'll explode).

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#27
For some reason, after reading the initial reporting on this system, I thought it was running against any photos on your iPhone, but now I read the actual paper, it seems like it only applies to photos destined to be uploaded to iCloud? So users can opt out by not using iCloud?

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#28
post #20

Earlier quoted context omitted.

Last year Sam Harris interviewed Gabriel J.X. Dance, the deputy investigations editor at The New York Times [0]. They speak to this. It's a tough episode to listen to - they cover many uncomfortable topics along this theme. From what I recall of the episode, porn (rightly or wrongly) is seen as opt-in for the participants. But if children are involved it cannot be opt-in and is more appropriately described as rape or…

Depends on age and context doesn't it? Is a 17 year old snapchatting their private parts to her 17 year old boyfriend CSAM? Should both parties be imprisoned and go on sex offenders registries for life?

Depends on the age of consent in both person’s jurisdiction and where they go with those pictures. My 16 year-old self got quite a lecture when my girlfriend and I took some pics of each other and my parents found them. (Age of consent was 13 where we lived, but it was 18 just up the road in another state).

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#29
post #27

For some reason, after reading the initial reporting on this system, I thought it was running against any photos on your iPhone, but now I read the actual paper, it seems like it only applies to photos destined to be uploaded to iCloud? So users can opt out by not using iCloud?

Also don’t upload to MS, Google, Dropbox as they also scan for CSAM.

Re: Apple's New CSAM Protections May Make iCloud Photos Bruteforceable

#30
post #27

For some reason, after reading the initial reporting on this system, I thought it was running against any photos on your iPhone, but now I read the actual paper, it seems like it only applies to photos destined to be uploaded to iCloud? So users can opt out by not using iCloud?

Yeah pretty much. Another way of thinking about it, is that to upload an image to iCloud, your phone must provide a cryptographic safety voucher to prove the image isn’t CSAM.
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