Thesis - Instituto de Telecomunicações

2.3. BEHAVIORAL BIOMETRICS 27situated in the class of soft-biometrics characteristics, since the error is near 20% EER.Advantages and Disadvantages A biometric method using the pointer, if used forauthentication in the computer or web environment, benefits from the non-intrusion giventhat it can be applied while the user is doing his normal activity at the computer. Themethod is easily adapted to continuous verification where long time acquisition improvesthe performance of the biometric technique.The drawback is that the method requires some time to get sufficient performance thatwould be unacceptable to use as a first biometric system to access physical infrastructuresor even to access the computer. We also note that the population that is able to interactwith the computer via a pointing device is relatively reduced when compared to physicalbased biometrics systems. The user behavior can be different in distinct pointing deviceinterfaces. Even in the same computer, for example a laptop, if the user interacts with thecomputer using the trackpad or a common external mouse he will present distinct behavior.2.3.6 EyeThe eye gaze has been used to find the place in the screen to where the user is directing hisattention [225], and in some implementation the eye could work as the pointer device in acomputer.We distinguish clearly that we are looking to the eye in the behavioral perspective,clearly differing from the iris or retinal pattern recognition systems that are physical basedbiometric techniques.The first known work is [174], where the authors identify characteristics that could beused to differentiate one user from another: each person looks in a different way.The eye movements, and not the position of the gaze, has been used to evaluate thecognitive performance of users in several cognitive intense tasks [209].The use of eye gaze dynamics for identity verification was introduced in [127, 128]. Theauthors study a population of 47 users while they perform a task of looking into a dot ina matrix of 3x3 dots. The users had to direct the eye gaze to the flashing dot from the 9in the screen. The user reaction time, the readjustment time and stabilization time weresome of the features extracted to perform the verification task. Preliminary results were