As you point out, there's a right way to do fingerprints, which Apple did. Only the key pair stored in the secure enclave is tied to your online identity. Ther

As you point out, there's a right way to do fingerprints, which Apple did. Only the key pair stored in the secure enclave is tied to your online identity. There is a missing link in the trust chain though, which is attestation of that secure enclave (how do we know it is a legitimate and uncompromised one?) However, privacy preserving attestation mechanisms such as DAA [1] require somewhat expensive crypto. [1] https://en.wikipedia.org/wiki/Direct_Anonymous_Attestation https://en.wikipedia.org/wiki/Direct_Anonymous_Attestation