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Comment by RenThraysk | Hacker News Reader

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RenThraysk

Would just upload the keys

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Presumably these keys live in a hardware security module on your phone called “secure enclave” and cannot be extracted

Ah yes, good point.

Is this module auditable though, or is "just trust us", like everything in the Apple world?

It’s auditable in the sense that there is a very high potential for reward (both reputationally and financially) for security researchers to break it.

The same reward exists with FLOSS, but it's much easier to audit, making findings more likely. Also, security through obscurity doesn't work.

If someone has a reliable and workable secure enclave hack they can become a multi-millionaire for selling to state actors or become one of the most famous hackers in the world overnight (and possibly get a life changing amount of bounty from Apple)

Basically it's not a hack someone just throws on the internet for everyone to use, it's WAY too valuable to burn like that.

An HSM bypass (extracting keys, performing unauthenticated crypto ops) on any recent iOS device is worth 10s of millions, easily. Especially if combined with a one-click/no click. In that sense, it’s auditable, because it’s one of the biggest targets for any colour hat, and the people smart enough to find a bug/backdoor would only be slightly aided by a spec/firmware source, and a bit more by the verilog.

This is true for pretty much every “real” hsm on the planet btw. No one is sharing cutting edge enclave details, Apple isn’t unique in this regard.

From the Advanced Data Protection whitepaper [0], it appears the keys are stored in the iCloud Keychain domain, so not the Secure Enclave:

> Conceptually, Advanced Data Protection is simple: All CloudKit Service keys that were generated on device and later uploaded to the available-after-authentication iCloud Hardware Security Modules (HSMs) in Apple data centers are deleted from those HSMs and instead kept entirely within the account’s iCloud Keychain protection domain. They are handled like the existing end-to-end encrypted service keys, which means Apple can no longer read or access these keys.

[0]: https://support.apple.com/guide/security/advanced-data-prote...

wrapped by a key hierarchy ultimately rooted by a key stored in the secure enclave.

Well yes, the entire storage is. I was trying to explain how it's extractable.

fair!

Apple can push firmware updates to the HSM just like the device. So if they really wanted they could add an operation that extracted the keys (likely by encrypting them to a key that lives in Apple's cloud).

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