Nation states almost certainly have the ability to extract the private keys out of an image sensor and SEP. Outside of superpowers even if you're willing to do it destructively.
They can then sign their own fraudulent images.
They can then sign their own fraudulent images.
That's not how this works.
Let's pretend they're able to extract the sensor key and the SEP key. Then what?
An attacker won't have the ECDSA P-256 over SHA-256 signed timestamp token from the Apple Push Notification Service.
When Reference mode starts, the operating system supplies a SHA-256 digest to be embedded at a fixed location in the captured frame’s metadata. The digest is computed from the most recent secure timestamp, the device manifest, and the device's secure boot manifest.
More encryption and checking happens until the secure digital negative is sent 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. Only if all these
checks pass does processing continue.
Sure they can, they have everything needed to prove to Apple's servers that they're a real iPhone since pulling the keys means they have the cryptographic root of trust, and Apple's servers will happily be a signature oracle for them in that case.
> When Reference mode starts, the operating system supplies a SHA-256 digest to be embedded at a fixed location in the captured frame’s metadata. The digest is computed from the most recent secure timestamp, the device manifest, and the device's secure boot manifest.
And when you know what is measured into those manifests and the keys at the root of trust you can manufacture those too.
The entire scheme is dependent on not being able to extract device specific keys. At the end of the day, those are almost certainly efuses burnt based on a on-chip HRNG as a manufacturing step which is intended to never leave the device, but instead only signatures and associated public keys.
But when you have chip development hardware of the kind you'd have at a decent fabless semiconductor company, you can very clearly see burnt efuses.
[1]: "How pixels become an Apple Reference Image" - https://news.ycombinator.com/item?id=49735284
We already know it's happening right now, and they know we know, but we can't do shit about it.
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 not a way to give the NSA that would help them. The system is setup so that the image data, meta data, etc can't be accessed by anyone including Apple.
(Similar to how many PGP hardware keys allow generating a private key on-device or writing your own provided key.)
- 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.
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; the private key is never disclosed. The public key is signed by the factory's certificate authority.
This ain't X.509 where VeriSign's key pair is sitting in a HSM at their HQ and in theory could be forced to sign a fraudulent certificate or revoke someone's valid website certificate.
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.