The Effect of Clock Resolution on Keystroke Dynamics

Abstract

Keystroke dynamics—the analysis of individuals’ distinctive typing rhythms—has been proposed as a biometric to discriminate legitimate users from impostors (whether insiders or external attackers). Anomaly detectors have reportedly performed well at this discrimination task, but there is room for improvement. Detector performance might be constrained by the widespread use of comparatively low-resolution clocks (typically 10–15 milliseconds).

This paper investigates the effect of clock resolution on detector performance. Using a high-resolution clock, we collected keystroke timestamps from 51 subjects typing 400 passwords each. We derived the timestamps that would have been generated by lower-resolution clocks. Using these data, we evaluated three types of detectors from the keystroke-dynamics literature, finding that detector performance is slightly worse at typical clock resolutions than at higher ones (e.g., a 4.2% increase in equal-error rate). None of the detectors achieved a practically useful level of performance, but we suggest opportunities for progress through additional, controlled experimentation.