Apple can synchronize the passkey between devices. As far as I understand I cannot. So I don't really understand how this can be said to be a hardware security token. It seems pretty clear that it is as far as I am concerned, but that Apple has nothing constraining them from copying my passkeys. Which seems like the worst of both worlds.

>So I don't really understand how this can be said to be a hardware security token.

No one claimed it's a hardware security token, but the private keys are stored in iCloud Keychain, which is end-to-end encrypted. Apple cannot access your private keys even if iCloud is compromised by an external attacker or employee.

If you're curious about the security engineering, you should watch the "Synchronizing secrets" part of this Black Hat talk from 2016: https://youtu.be/BLGFriOKz6U?t=1353 or you should read the "Synchronization security" section of the "About the security of passkeys" support doc: https://support.apple.com/en-us/HT213305

But Appel could deactivate E2E encryption without your knowledge to get all your keys. For instance on request of government agencies.

This is indistinguishable from the "I don't trust my computer" threat model. Apple could also surreptitiously scrape your screen or copy your processes' memory.

It’s not, because law enforcement considers your computer as private property, while anything you upload on the cloud is seizable without warrant. I’m not joking, it was rapported on HN at the time of the Snowden leaks that NSA can legally monitor your data as long as you transmit it over the wire.

The difference is the effort it takes. Deactivating E2E is just a flag.

There is no need to mess with the E2E, the client installed on your machine is downloaded form their servers, they can just copy the data when it is decrypted locally.

I does not make sense to use a proprietary internet connected application on your machine and worry that that the servers might be nefarious.

If your threat model includes getting hacked by the government, then your only choice of OS would be some hardened open source OS with fully reproducible builds and no proprietary driver blobs installed.

And in which you have personally audited every line of code for extra confidence. /s

You can use 3rd party password managers to sync your passkeys however you please.

Apple has no access to keychain data: https://support.apple.com/en-us/HT213305

Could you give an example? That support article doesn't mention anything about it. I do recall reading something about that recently, but I read the article and it it made no mention of what syncing passkeys actually means. It sounds like theoretically I could write an app that uses the same APIs Apple uses to sync encrypted credentials between TPMs. But "however you please" sounds suspiciously like "however you please, as long as you don't sync it to anywhere Apple can't vouch for the safety of the keys."

Which again, seems like the worst of both worlds.

It has been a while since I have dug into it, but from what I remember it works roughly like this:

You login to iCloud which gives your device write access to iCloud storage. The device creates a private key inside the TPM, and uploads the public key. When you add a new device, one of your existing devices has to use its hardware key to sign your new devices key. It also must be signed by a second key derived from your iCloud password (so you). Apple doesn't go into the details on this, but I believe the originating TPM also signs the key with a chain of trust that goes back to Apple itself.

The keychain is encrypted locally and exported to iCloud. The key used to encrypt the keychain is also encrypted using the public keys of all trusted device keys in iCloud that have both a signature from another trusted device and from you.

As a user you can also just open up Keychain Access on a Mac and ask it to generate a CSV export of your entire iCloud keychain - which is how you would go about migrating to another password manager.

I'm sure that works for passwords. I am skeptical that it works with passkeys. It's unclear to me if the CSV will include passkeys. It's additionally unclear to me if I enroll in some website with a passkey stored in my Keychain, and then export and import that password into some other password manager, if the website will accept a login from the exported passkey. Definitely, there's the "attestation" piece and services might choose not to accept the passkey if the attestation has changed. You can blame the service - but it seems like an intentional design goal here. And it has been said that Apple didn't want attestation, maybe it will be removed, but it's there and it seems likely to be used.

Except that passkeys are treated as both a password and token at the same time. They are the sole thing needed to access a website, so you are absolutely storing your credentials with a large tech company.