Feat/add biometric gating

[sbycrosz]

Short description

Add options to add biometric gate before generating signature so that authentication is cryptographically tied to the key use rather than being an application level check

This follows the OWASP best practices regarding local authentication

The tester should be aware that local authentication should always be enforced at a remote endpoint or based on a cryptographic primitive. Attackers can easily bypass local authentication if no data returns from the authentication process.

Changes

• New requireAuthentication option. When set, signing only works after a successful biometric prompt
• New invalidateOnEnrollmentChange option. Invalidate the key when new fingerprint/face is added

How to test

Needs a real iOS/Android device, probably won't work on simulator.

1. Run the example app
2. Old keys should keep working, nothing changes for them
3. Keys made with requireAuthentication: false should sign without any prompt
4. Keys made with requireAuthentication: true should only sign after the biometric prompt passes