User authentication device and image forming device

A user authentication device comprising:

• a user authentication setter that enables or disables a predetermined plurality of authentication methods;
• a user authenticator that accepts user authentication by an authentication method that the user authentication setter enables;
• a display that displays various information to a user;
• a processor;
• and
• a computer-readable medium storing instructions that, when executed by the processor, cause the processor to control the user authentication setter, the user authenticator, and the display,
• wherein, when the user authentication setter accepts a setting that enables a single authentication method among the plurality of authentication methods, the processor controls the user authentication setter to disable all authentication methods other than the single authentication method, and the user authenticator accepts only user authentication by the single authentication method, and
• wherein a degree of a security level of each of the plurality of authentication methods is predetermined, and when an input portion accepts an input to enable an authentication method with a security level lower than a security level of a currently enabled authentication method, the processor controls the display to display a notification that a switch is made to an authentication method with a low security level and then the input portion accepts an input to enable the switch of the authentication method, and the processor controls the user authentication setter to enable the authentication method, and
• when the input portion accepts an input to enable an authentication method with a security level not lower than the security level of the currently enabled authentication method, the processor controls the user authentication setter to enable the authentication method without any notification to the user and without requiring any input to enable the switch of the authentication method.