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Comment by jakob223 | Hacker News Reader

What's to stop apple from registering another device on your account, which will get the shared keys?

color me skeptical.

I stopped using iPhone. However, I believe they did at least ostensibly fix that problem by not trusting new devices added until you trust it on at least one other device that already has the keys.

I think the last remaining piece of trust is trusting that Apple's servers are correctly advertising your iMessage public keys, at least if I'm understanding how it works correctly.

After all, if you lose access to all devices you can still reset from scratch and get back on iMessage and at least receive messages. Your recipients won't know this happened. How would anyone know if Apple is performing a MITM using this mechanism?

If it's like how iCloud Keychain works now, you have to approve the new device on every existing device, and I believe each device pair generates keys known only to them.

Apple can't simply register devices into your account, they would have to have access to your iCloud account, which they can only get using one of those keys.

I guess if the devices are only willing to share keys with other devices which can individually prove they have the iCloud password. I wonder if it's an online procedure or if they just upload the keys to iCloud, encrypted with the user's iCloud password.

When registering a new device you have to authorise it using one of your existing devices.

This can be fixed by asking for confirmation on every device in the same ring when a new device is added. Only after confirmation the keys get shared.

That's not really feasible if the loss of one key means all data is kaput

Don't you need to access the secure enclave on an existing device to do that now?

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