A method can include receiving user input values via a plurality of inputs of a motor vehicle and determining if each received user input value corresponds to an authenticated user value in a secure memory of the motor vehicle. For each received user input value corresponding to an authenticated user value, a certainty factor corresponding to the authenticated user value can be accessed from a secure memory. A certainty score can be generated from all accessed certainty factors. Each of a plurality of permissions for operating or accessing the motor vehicle can be enabled in response to a comparison between the certainty score and a certainty threshold assigned to each permission. Corresponding devices and systems are also disclosed.