An image processing apparatus of one embodiment includes an image processing unit and a controller. The controller receives biometric information for a user for a logon operation and re-orders user record entries in a table when a predetermined condition occurs. Each record entry in the table includes reference biometric information in association with user information. The re-ordering of the entries is based on user information stored in the user record entries. After the re-ordering of the user record entries in the table, the controller performs an authentication operation that includes comparing the received biometric information to reference biometric information in the re-ordered user record entries of the table until a match is determined.