New generation devices are pervasive in nature and provide anumber of security sensitive functionalities, which might expose the userprivate information to serious security and privacy threats. The maincountermeasure used to prevent unauthorized access is the user authen-tication. Most of these devices are still protected by traditional authen-tication mechanisms (PIN, password), which are exposed to well knownsecurity limitations. These issues are mitigated by the introduction ofnew physical biometric authentication mechanisms. Biometric authenti-cation, basing on user physical traits and requiring the user presence atthe authentication time, makes the system more secure. Despite the newmechanisms overcome some data security issues, they still suffer fromother usability problems. In this paper we explore a new unobtrusiveauthentication mechanism based on human behavior.