Bionetrics are never going to be able to be used to directly produce a strong key, so it always reduces to a question of how secure is the enclave, and bugs in

Bionetrics are never going to be able to be used to directly produce a strong key, so it always reduces to a question of how secure is the enclave, and bugs in the pattern recognition. In this case there was no Secure Enclave at all. If you do have a enclave you trust to keep a private key safe, my preference would always be to use a simple (not trivial) password/passcode and depend on strict rate limiting. The only way to avoid a private key being stored in an enclave is to derive the key from a strong password. This avoids the whole class of key extraction attacks but, now there is a password that can be attacked offline. If you combine a decent password with an online hardening / rate limiting system then I think you have something which stands a chance. But I’m building a commercial product in exactly this space, so I’m not entirely unbiased.