At a mobile device, a password is used to create a proof of knowledge (POK). The POK is stored in a controller accessible via a communication network. The POK ensures that the controller can detect an incorrect password from the mobile device, and that the mobile device cannot be subject to a brute force attack to determine the DC stored in the mobile device. After a predetermined number of unsuccessful attempts to enter the password, the controller blocks further attempts, thereby restoring protection against a brute force attack that was lost going from a standalone smart card to mobile-device-based derived credentials. A portion of Derived Credentials, needed to authenticate the user of a mobile device, is stored in the controller, further increasing the difficulty of unauthorized use.