Ken Horii

Evaluation on a keystroke authentication system by keying force incorporated with temporal characteristics of keystroke dynamics

This paper presents the study to develop and evaluate techniques to authenticate valid users, using the keystroke dynamics of a users PIN number entry on a numerical keypad, with force sensing resistors. Added with two conventional parameter lists of elements, i.e. digraph latency times and key hold times, keying force was chosen as a third element. Two experiments were conducted. The first experiment was to evaluate whether the three types of elements derived from keystrokes have a significant effect for subjects and to examine how trials and session effects generated the variation of the three elements. The second experiment was to demonstrate the system performance by calculating the False Rejection Rate (FRR) and the False Acceptance Rate (FAR) of the system. In the second experiment, a total of 20 keystrokes were recorded from each subject one week after the memorizing session, in order to evaluate the FRR of the system. To evaluate the FAR of the system, the subjects pretended to be impostors, and therefore they repeatedly watched videotaped pass trials made by a valid user as many times as they desired, and tried to imitate the keystroke dynamics of the valid users. The subjects keystrokes were then evaluated on whether they could fool the system. The first experiment, ANOVA revealed that a significant effect of subject was found on each of all three elements. Trial was not significantly affected to digraph latency times and peak force; however, it was significantly affected to key hold times. There was a trend that keystroke dynamics characterized by each element showed reformation of their patterns and reached a steady state over the 10 weeks of experimental sessions. The results of the second experiment showed the average equal error rate to be 2.4%. The results of system performance were compared with those of other studies and concluded that it was difficult to obtain enough information to behave as a perfect impostor by monitoring the videotaped keystrokes.

Design of Eye-Typing Interface Using Saccadic Latency of Eye Movement

The objective of this study was to construct and empirically evaluate an improved, online eye-typing interface with respect to its practical usability. The system used the concept of saccadic latency, a silent period of 200 to 250 msec precedes the initiation of a saccade, for identifying the users intentional text entry. Ten individuals participated in the experiment that was conducted on 2 consecutive days, with three blocks of trials conducted on each day. A block included five trials, each of which involved completing the text entry of a short sentence using this eye-typing interface. The proposed interface was evaluated by the users performance based on indices including typing speed and an error index. For defining the error index, the overproduction rates (ORs) were used. The results showed an average OR of 0.032 and average typing speed of 27.1 characters typed per minute. The result revealed that the typing speed changed as an effect of participant, day, and block. The characteristics of the proposed interface with the related characteristics of an eye-typing interface were summarized to discuss a further study for the eye-typing interface.

Hands-free data manipulation for visual inspection system by using temporal characteristics of saccades

In some industrial inspection processes, multi-process, handling workers are required for entering the results of visual inspection tests without using their hands, for efficiency or hygiene reasons. We developed a hands-free visual inspection system by using temporal characteristics of saccadic eye movements. The proposed system is free from the Midas touch problem, i.e., the difficulty in developing an eye-typing interface owing to the difficulty in differentiating between intentional blinks and gazes and natural ones. For verifying the system, an experiment was conducted where five subjects performed a visual inspection task. The average defect detection rates were 85.8%, and no Midas-touch-related errors were observed. Results of error analysis showed that redesigning of the system interface would lead to an enhancement of the system performance.

A Study on Fundamental Information Transmission Characteristics of an Air-Jet Driven Tactile Display

There are many people with impaired vision as well as hearing. Tactile displays can be useful to such people for communicating by means of characters and shapes. Many devices for tactile displays such as oscillators and electrocutaneous stimulators have been developed. However oscillators have two drawbacks: physical stress tends to build up in actuators because of long term exposure to oscillations, and they may transmit erroneous information because of unstable contacts between magnetic pins and the skin. Moreover, electrocutaneous stimulators cause discomfort to the user. In this study, we have developed a tactile information presentation technique that uses air jet stimulations and tactile phantom sensations induced by a complex combination of tactile perceptions. The tactile display can transmit information to the skin without physical contact and is free from the restriction of pitch size. In this paper, we have examined its fundamental information transmission characteristics.

Computer task-based evaluation technique for measuring everyday risk-taking behavior

Human risk-taking behavior is a major factor for accidents. Several techniques for quantifying human risk-taking tendency include questionnaire and observation methods. These techniques, however, have been questioned their validity and reliability. Our objective was to propose and evaluate a computer task-based evaluation technique for measuring everyday risk-taking tendency. In this technique, the users perform tracing a certain length of pathway, from start to goal, shown on the display by mouse. The system monitors the trajectory of the mouse cursor and detects the point of decision-making when users change their strategy from steering motion to ballistic motion as the mouse cursor approaches to the goal, yielding the level of risk-taking behavior represented by the Index of Difficulty (ID) at the location of strategy change. The results of experiment showed that IDs were highly correlated with probabilities of risk-taking behaviors obtained from 16 question items.

Influence of Reaching Actions on Driving Performance

Drivers have various additional actions while driving, which do not belong to operations of a vehicle, for example, eating, drinking, pressing some buttons, and exchanging compact discs in a car audio system. These actions cause traffic accidents, because they used to distract driver’s vision and decision making. Moreover posture of the driver during the actions influences driving operation seriously. Therefore, we focused on reaching actions while driving. In this paper, we investigated driving performance with reaching tasks using a simplified driving simulator. Furthermore, we examined influences of the additional actions on the driving performance with parameters of a driver-vehicle model.

Representation of Velocity Information by Using Tactile Apparent Motion

The objective of the study is to evaluate whether use of apparent motion can be an effective presentation method for velocity information. Ten subjects participated in the experiment where they perceived apparent motion generated by air-jet and they controlled the speed of the moving object on the PC screen to express their perceived velocity. As a result, perceived velocity decreased significantly as the ISOI was increased. Perceived velocity changed with the duration when the ISOI was between 30---70 ms and when apparent motion was provided. Duration only affected perceived velocity when apparent motion is provided to the subjects. In conclusion, apparent motion generated by stimuli can be effectively used to transmit precise velocity information tactually.

Accuracy of Velocity Perception Generated by Tactile Apparent Motion

The objective of this study is to empirically compare the accuracy of velocity perception generated by visual apparent motion with that generated by tactile apparent motion. From the results, the subjects were able to perceive velocity information through tactile stimulus presentation more accurately than through visual stimulus presentation. When tactile stimuli were presented, the effect of apparent motion enhanced the accuracy of velocity perception; however, this was not the case when the stimulus sets were visually presented.

Relationship between Pinch Width and Secure Force Exertion during Holding Objects

In this study, whether or not the pinch width affects the pinch force to be securely exerted was investigated. We focused especially on individual pinch width when the muscle are relaxed, which is defined as Natural Opposition Distance, rather than the span determined by the object in the conventional approach. A total of 10 subjects participated in the experiment where their individual NODs were measured with the CyberGlove system. Objects with different pinch width including individual NODs were used for measuring secure force of 1-point pinch grip. The results of ANOVA showed that the difference in pinch width did not influence secure force. All in all, results of our experiment implied that the difference in grip span has less influence on force exertion when the exertion is submaximal.

Three-element schema technique in schema-based user interface design

Abstract TeST, or ‘the Three-Element Schema Technique’, is a new method for user-interface designing for software applications. This technique employs a cognitive viewpoint utilizing three different elements, namely, Object-schema, Attribute-schema and Method-schema. These comprise what has been traditionally known as commands that a user issues in order to perform his/her work on the computer. Three concepts are introduced in the technique, ‘Cells’, ‘Units’, and ‘Cores’. The first two concepts are used in determining the application structure and the third logically deduces four types of user interface. The authors studied the structure of commercial applications and found that they were designed using at least two of these user interface types.