Methods and monitoring units for safety-relevant graphical user interfaces

A method and monitoring unit for security-relevant input on a graphical user interface are provided. A computer generates image data that are transmitted to a display via an image data line. The user interface has at least one graphical operator control element that is selectable by an input device. A monitoring unit is connected to the image data line and reads image data for a security function. The monitoring unit is supplied with input information from the input device, and is connected to a confirmation apparatus via a secure signal path for user confirmation. The monitoring unit ensures and/or checks whether a detected selection of the operator control element is represented correctly, and, in the event of a user confirmation for a represented selection of the operator control element, enables or triggers an associated security-relevant operator control command. This allows secure input even with non-security-certifiable input devices.