Per this: https://www.slashid.dev/blog/passkeys-deepdive/

The private key is both kept in your phone’s Secure Enclave and stored in iCloud, so strictly speaking the implementation isn’t hardware-bound in that case.

But I think the intended point is something more practical: can you, as a user, export the passkey to be shared on your non-Apple laptop, phone, etc? And maybe I’m mistaken, but I’ve been under the impression that you cannot.

Given it sync from iCloud, you probably could export with enough prying at the MacOS Keychain app, but exporting them out is not a supported use case yet.

If macOS can download it from iCloud, with enough reverse engineering you should be able to use the same APIs.

Unless iCloud only lets you download it in a form only the secure enclave can decrypt.

I'm pretty sure my 2017 Macbook Pro (Intel, no Touch Bar) doesn't have a Secure Enclave chip, yet it supports Passkeys.

Hi,

I'm the author of the SlashID blogpost. You are right, the WebAuthn standard doesn't provide any guarantees on the authenticator storage security hence passkeys (and WebAuthn creds) can be stored in anything that speaks CTAP2.

We wrote a follow-up blogpost talking about the threat model in which we touch on the above: https://www.slashid.dev/blog/passkeys-security-implementatio...

Hi,

I'm the author of the blogpost. You are spot on, Passkeys are exportable so the private key ends up both on iCloud and the Enclave/authenticator.

My understanding is that there's chatter about cross-vendor synchronization of passkeys but nothing concrete yet.

Meanwhile Apple allows people to share Passkeys via AirDrop (Settings > Passwords - select the passkey you want and click the "Share" icon to send it over Airdrop) so it should be possible with some effort to obtain the private key with something like this: https://github.com/seemoo-lab/opendrop. Haven't done extensive testing yet though, so I can't confirm.

Would love to hear if anybody knows more about how the sharing via AirDrop is implemented/protected.

Generally, the idea is that the private keys are stored on a TPM chip so they cannot be exported for security reasons, similar to a YubiKey or a crypto wallet. I know Apple and Google are looking into trying to allow users to somehow export these keys elsewhere, but I'm uncertain how easy that will be or what tradeoffs there will be. I'm skeptical that Apple and Google will try to make it too easy since they benefit from user lock-in, but I would be happy to be proven wrong.

As far as I can tell both Google and Apple have a mechanism to export the key so you can replicate the same key to another device. I run into this same situation with "HSM clusters" sold in enterprises where I don't really understand how people can claim with a straight face that you can't export the key to another device when they just explained to me that they export the key to another device.

That is not Apple’s stated design at all. If you read Apple’s passkeys security document, it claims that the private keys are synchronized with iCloud and are recoverable following the loss of all devices. Non-exportable passkeys using the TPM is an HN myth.

> I'm skeptical that Apple and Google will try to make it too easy since they benefit from user lock-in, but I would be happy to be proven wrong.

https://hachyderm.io/@rmondello/110329118270492669

Apple's existing password manager (which is what surfaces passkey management) lets you export and import the database as a CSV file, same as Google and many others. I suspect the biggest missing piece is an agreement on an interoperable format - likely one that would also be interoperable for password and TOTP exchange as well.