Users of portable computing devices, such as laptops, tablets, smartphones, and gaming systems routinely employ owner authentications on their devices to protect personal data and prevent unauthorized access. To meet the growing security and privacy needs of the users, owner authentication of an electronic device may be carried out through one or multiple forms of biometric identifiers, which can be used in addition to conventional password authentication methods. A popular form of biometric identifiers is a person's fingerprint pattern. A fingerprint sensor can be built into the electronic device to read a person's fingerprint pattern so that the device can only be unlocked by the device owner through authentication of an authorized person's fingerprint pattern. Notably, a fingerprint sensor can be built into a smartphone with a touch screen so that a screen-locked smartphone can be unlocked by simply touching a button with a finger without entering a passcode.