Thread

1. tgsovlerkhgsel · 1789535685 · focus · HN ↗

   This is really clever from Apple. The journalist use case is just the PR story. This will be really useful for identity verification and insurance apps, and has the potential to shift from "you need a smartphone to be able to live normally" to "you need an iPhone to be able to live normally".

   There are already plenty of insurances that require you to submit claims through a smartphone app that tries to essentially do this by capturing sensor metadata etc. - those don't need to be nation-state resilient, just Joe the Crackhead Insurance Scammer resilient, so this works. Likewise, more and more things online require identity verification (either officially or disguised as age verification).

   Edit: And while "a nation state actor can spoof this" is a problem for the journalism use case, the insurance/ID verification use cases are perfectly fine with anything that raises the bar but could be bypassed with enough effort. Also, the journalism use case suffers from the same fundamental issue all of these use cases suffer from: People will "verify" the picture by looking at the repost of a screenshot of the verification UI, not by verifying the original themselves.

   1. alwillis · 1789551144 · focus · HN ↗

      > This is really clever from Apple. The journalist use case is just the PR story. This will be really useful for identity verification and insurance apps, and has the potential to shift from "you need a smartphone to be able to live normally" to "you need an iPhone to be able to live normally".

      You have it all wrong.

      Apple Reference Image is not an id system; it's primarily a way to attest that the pixels recorded by the camera sensor have not been altered in any way; the pixels, metadata and timestamp are all cryptographically signed.

      There's no way to link a reference image to a person; it's also not possible to determine if a pair of images came from the same device.

      > And while "a nation state actor can spoof this" is a problem for the journalism use case

      This is incorrect:

          When the image sensor is first initialized in the factory, it creates a
          cryptographic signing identity, sharing only the public key with the
          factory. The SEP similarly creates a separately-attested signing
          identity. These identities are bound together into the device manifest,
          allowing us to later check whether a particular sensor and SEP are from
          the same device.
      
          The final signature on a reference image is a composite post-quantum
          signature combining RSA-3072 and ML-DSA-87. To our knowledge, Apple
          Reference Image is the only image provenance system that provides
          quantum-secure defenses.
      

      So… a nation-state can't really do anything here unless they acquire alien technology. If something crazy happens (solar flare or EMP?), a fraudulent reference image can be revoked.

      > Also, the journalism use case suffers from the same fundamental issue all of these use cases suffer from: People will "verify" the picture by looking at the repost of a screenshot of the verification UI, not by verifying the original themselves.

      I would imagine there will be a way to confirm an Apple Reference Image on the web. Pretty soon, 3rd parties will be able to verify the image themselves:

          Reference images can be viewed in the Photos app alongside the main
          image, like a digital negative, to visually compare the two assets and
          determine if any edits were made. APIs are available in iOS, iPadOS, and
          macOS 27 for third-party apps to enable viewing of these reference images.

      1. coldtea · 1789559032 · focus · HN ↗

         >There's no way to link a reference image to a person; it's also not possible to determine if a pair of images came from the same device.

         Apple knows the iphone the reference image was uploaded from, so, yes, there is.

         1. jclardy · 1789561873 · focus · HN ↗

            It doesn't, as it is run through an Oblivious HTTP relay run by a third party before getting to Apple's servers. So it has no IP information, and the requests use anonymous access tokens.

            It is probably possible for an entity to break it, but it would require live access to both Apple and the third party (Likely Cloudflare) servers. And that is assuming there is only one third party routing OHTTP requests, otherwise you would need to monitor all of them, in real time, since the requests are transient.

            1. cobbzilla · 1789575786 · focus · HN ↗

               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.

               1. alwillis · 1789583350 · focus · HN ↗

                  > 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 takes place on PCC are all device-agnostic.

                  The reference image is processed and eventually signed by Private Cloud Compute's post-quantum signature using a hybrid MLDSA87-RSA-3072-PSS-SHA512 scheme.

                  So… it's not possible for Apple to know if two images came from the same iPhone.

                  1. microtonal · 1789630715 · focus · HN ↗

                     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).

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