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Apple Reference Image: A New Approach for Verified Photography

security.apple.com

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Re: Apple Reference Image: A New Approach for Verified Photography

#351

Post by brookst »

BugsJustFindMe wrote: post #30
brookst wrote: post #27

Earlier quoted context omitted.

Thought about it and also are bright enough not to fall for the “if a single person dies wearing a seat belt, we should abandon seat belts because they do no good at all” fallacy. It’s almost certainly possible to fool v1 of this system, for some images, in some contexts. It would be shocking if the first implementation was completely perfect. But maybe it’s better than nothing?

> But maybe it’s better than nothing? I think this will depend on how it gets used. I can imagine numerous outcomes where it's in fact worse than nothing (significantly more effective blackmail, for instance).

I guess? The bailey version of that argument is that we should do away with the concept of truth altogether, because some truths are harmful.

Re: Apple Reference Image: A New Approach for Verified Photography

#352

Post by microtonal »

JumpCrisscross wrote: post #283
slester wrote: post #277

Earlier quoted context omitted.

Why would anyone be using images of government IDs when modern documents have NFC chips with the data, signed and with anti-cloning mechanisms on them? If they can verify an Apple Reference Image they can verify an NFC document.

> If they can verify an Apple Reference Image they can verify an NFC document Interfacing with images is easy. Interfacing with NFC takes work. I have experienced precisely zero identity-verification workflows which NFC'd anything, and that includes my banks, which could easily ask for my debit card's NFC but don't.

My credit card company’s app (in Europe) reads my ID through NFC when logging in for the first time (besides requiring ID photos).

Our national app for logging into government sites and confirming things also requires a step where the ID’s NFC is read to reach the highest trust level.

So it’s definitely becoming more and more common here.

Re: Apple Reference Image: A New Approach for Verified Photography

#353

Post by microtonal »

alwillis wrote: post #313
autoexec wrote: post #281

Earlier quoted context omitted.

The NSA has probably already forced Apple to hand the keys over to them.

> The NSA has probably already forced Apple to hand the keys over to them. Again, that's not how it works. There's no set of keys and certificates they could give to the NSA. Every iPhone 18 Pro and Pro Max has a unique set of cryptographic keys, most of which can't be accessed by Apple. The first thing that happens is when photo sensor is initialized at the factory, it creates its own ECDSA P-256 signing key pair; t…

They don’t need the signing keys though. Apple could roll out a separate version of sepOS to assist law enforcement that signs at they will.

Also, while the unique device ID is supposed to be burned into fuses by the SE during production, it is kinda hard to prove for anyone that is not Apple that this indeed happens in the way they state.

Personally I’m not a strong believer in such theories though. I think it’s more mundane and Apple helps law enforcement by having some weak defaults. Like how iMessage is end-to-end encrypted, but most chats are available to law enforcement because most people turn on iCloud Backups/Messages in iCloud and not ADP, resulting in chats only being encrypted at-rest in iCloud. This is only stated somewhere in a footnote in one of their security documents.

There are more weak defaults like that in various crucial apps (e.g. WhatsApp) that makes most important stuff available to law enforcement when needed.

Re: Apple Reference Image: A New Approach for Verified Photography

#354

Post by microtonal »

alwillis wrote: post #346
propaganja wrote: post #311

Earlier quoted context omitted.

Apple would be legally restricted from disclosing any government compromises, while still claiming their systems are secure and operating as intended in general. We already know it's happening right now, and they know we know, but we can't do shit about it.

> Apple would be legally restricted from disclosing any government compromises, while still claiming their systems are secure and operating as intended in general. I'm aware. The point is they can't give the NSA something they don't have. The photo sensor generates its own ECDSA P-256 signing key pair and never releases the private half. Every device has a unique key pair and the private key is unavailable… there's n…

I believe them, but the process is hard to check. How do we verify that they don’t have the sensor burn in a private key generated by them?

(Similar to how many PGP hardware keys allow generating a private key on-device or writing your own provided key.)

Re: Apple Reference Image: A New Approach for Verified Photography

#355

Post by microtonal »

alwillis wrote: post #320
cobbzilla wrote: post #275

Earlier quoted context omitted.

Apple gets the device-signed image and replaces with a PCC signature to preserve anonymity. > The final reference image is instead signed by Apple’s signing service, after validation by PCC. So, if compelled, Apple could theoretically tell someone if two images came from the same camera.

> So, if compelled, Apple could theoretically tell someone if two images came from the same camera. No they couldn't. If you generate two SSH key pairs on your laptop, there's no way to confirm they were created on the same machine. There's no device identifying data in a reference image, which is the point. The factory signature, the image sensor key, the Secure Enclave Processor key and all of the signing that take…

I am not sure I follow. The private keys in the image sensor and the SEP are static, so you can see that two images are signed with the same private key. Apple 'decorrelates' this by letting PCC verify the signature and then replacing it by their own signature:

When the user initiates developing a reference image, the device uploads the secure digital negative to Private Cloud Compute. PCC recomputes the digest embedded in the frame and verifies the sensor's signature over the pixels and that digest, verifying the certificate chain back to the sensor CA. PCC also verifies the SEP signature and chains it to the BAA CA, and it verifies the signature on the device manifest and chains it to the CA that signs device manifests at the factory. It then confirms that the sensor and SEP named in those chains belong to the same device. [...] If these checks pass, PCC then submits the commitment to our signing service, which signs it with a composite post-quantum signature using a hybrid MLDSA87-RSA-3072-PSS-SHA512 scheme. The signature is embedded in the JPEG, and the reference image is returned to the device, which associates it with the main photo from the original capture.

After the secure digital negative is successfully developed, it's automatically moved to the deleted photos folder."

So in the end it all depends on how much you trust Apple's cloud and PCC nodes. If there is a weakness in their services, Apple could record both the original signatures and their signature, and could prove whether two photos were made using the same lens/device and they could even trace it back to a specific device (by looking up the original signature + signing identity given their signature).

Re: Apple Reference Image: A New Approach for Verified Photography

#356

Post by microtonal »

alwillis wrote: post #315
mitxela wrote: post #178

Earlier quoted context omitted.

You'll still need an iPhone, the verification is linked to the specific iPhone, and the specific iPhone is linked to you.

The reference image isn't linked to any particular iPhone or person: We built Apple Reference Image to avoid using an explicit, public credential for photographers, and to avoid even implicit public association between different photos taken by the same sensor. The final reference image is instead signed by Apple’s signing service, after validation by PCC. That signature is backed by Apple’s strongest technical guara…

The reference image isn't linked to any particular iPhone or person

It is for Apple, to the extend that if there are backdoors and weaknesses in their PCC, they could register a device signing identity to Apple signature mapping.

I think the line of reasoning is that you have to trust Apple anyway, since they could also roll out a malicious image to your particular phone, but I still feel like PCC is much harder to verify/audit than an iPhone already is.

Re: Apple Reference Image: A New Approach for Verified Photography

#357

Post by microtonal »

alwillis wrote: post #348
propaganja wrote: post #311

Earlier quoted context omitted.

Apple would be legally restricted from disclosing any government compromises, while still claiming their systems are secure and operating as intended in general. We already know it's happening right now, and they know we know, but we can't do shit about it.

Here's a flow chart; tell us at what point there's something Apple can be compelled by a 3-letter organization to produce: https://news.ycombinator.com/item?id=49735284

I think the chart exactly shows the weakness that some people have pointed out. Apple's PCC servers at some point in time know the signing identity for a photo and Apple's generated replacement signature. The relevant steps from your chart:

- verifies each link and its certificate chain, sensor signature over pixels, SEP signature, device manifest signature

- PCC Submits the commitment (the JPEG hash) to Apple's signing service.

So, at some point in time, Apple's servers have both the original certificate chain and the new replacement signature. If this is recorded, Apple can deanonimize photos and check whether two photos were from the same device/sensor.

Apple's system protects against most state actors, except Apple and the US, unless you fully trust that their PCC is watertight.

(Remember that Apple was part of PRISM and probably also its successor.)

I don't think law enforcement needs it, because when sending/posting a picture, people leak so much metadata anyway.

But people outside the US should certainly distrust these systems.

Re: Apple Reference Image: A New Approach for Verified Photography

#358

Post by microtonal »

ozlikethewizard wrote: post #122

Somewhat tangential but is "most secure consumer mobile device" actually correct? Does an iPhone beat out a grapheneOS android, or would that not be considered consumer because of aftermarket changes? Seems like a pretty bold claim but I know apple is pretty damn good with security (as long as you dont count Apple as a security risk themselves)

From leaked Cellebrite presentations, it seems GrapheneOS is more secure. But it's easy for Apple marketing to move the goal posts by adding words like 'consumer'. They do this all the time in their marketing, like:

Force sensor with volume swipe arrives on AirPods 5, a first for the open-ear form factor, adding the ability to quickly adjust volume by swiping up or down on the stem.

Add some qualifiers so that you can call yourself 'first'.

Re: Apple Reference Image: A New Approach for Verified Photography

#359

Post by albert_e »

mayhemducks wrote: post #332
albert_e wrote: post #256

Thinking aloud about failure modes / edge cases: If i create a high quality deepfake image, project it on a large screen and take a photo of that image with an iPhone (+apple verified image secure tag) ... would that resulting image be considered "authentic" by default? Would digital forensics accessible to lay people still be able to fact-check and call out misuse / fakery of the new secure tag.

The system is not for detecting deepfakes. It is for proving that the data captured by an apple camera's sensor was not altered by some 3rd party hardware or software chain.

Fair enough.

So the chain of trust is ...

Personal credibility of the person taking the photo with iPhone (till the moment picture is taken) + tamper-evident protection against unauthorized or anonymous edits and manipulation (after the iphone photo is published and circulated)

Apple cannot (of course) vouch for the former.

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