More Entropy for Login Keys

Problem:

Generally, neither the username nor the password provides good entropy. The only rule imposed on the password is that it should have a minimum length of 8 characters. Therefore, weak passwords such as password are accepted.

Consequences:

We use Scrypt(password, username + InstanceSalt) to generate the login keys (master keys). Since these master keys are not generated from a good source of randomness, attackers can gain access to all documents of users with weak passwords.

A side consequence is that the probability to register a new account with the same username and password combination is not negligible. If this happens, then users without bad intentions get access to a third person's drive.

Suggestions:

Use password strength estimation such as zxvbn-ts ^[1] which rates the password strength on a score from 0 to 4 and provides, guessing times, indicators what makes the password weak and how it can be improved. We may display the password strength estimation and/or require a minimum score.

Drawbacks:

Users are annoyed by password requirements.