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trailofbits / SecureEnclaveCrypto

Demonstration library for using the Secure Enclave on iOS
Apache License 2.0
279 stars 41 forks source link

Clarify TouchID vs. device passcode use cases #1

Closed suzukieng closed 7 years ago

suzukieng commented 8 years ago

The sample code currently shows only the TouchID use case, even though in the implementation of KeyInterface there is a generatePasscodeKeyPair method, but it is not exposed publicly.

As far as I understand it (correct me if I'm wrong), you can also use the passcode as authentication to protect the private key. The private key will still be non-extractable and stored in the secure enclave. The main drawback I see here is that by using the device passcode instead of TouchID is that the passcode is entered by the user through a UI and thus passes through the user space and kernel space, whereas the TouchID interaction will remain completely in the secure enclave.

I think you should either mention this as a (less secure) option or drop the generatePasscodeKeyPair method in the implementation altogether.

hfossli commented 7 years ago

I think the new api I've provided in swift adresses this in a good way. Let me know what you think.

hfossli commented 7 years ago

Feel free to reopen if you feel this isn't addressed in the swift api.