Mitigating attacks based on knowing the length of a Windows Hello PIN - The Old New Thing
Mitigating attacks based on knowing the length of a Windows Hello PIN - The Old New Thing
Balancing convenience against security, and how you can tune the knobs toward more security.
Describes considerations of convenience and security of auto-confirmation while entering a numeric PIN - which leads to information disclosure considerations.
An attacker can use this behavior to discover the length of the PIN: Try to sign in once with some initial guess like “all ones” and see how many ones can be entered before the system starts validating the PIN.
Is this a problem?
Knowing the length of a random pin/password is roughly as valuable as knowing one of the characters, if it's a concern just make it two longer and you have just improved security.
I don't know how that applies to non-random pins/password.