## 3 Design and Implementation
### Classification Algorithm
[26], an ideal authentication system needs to provide features such as no unauthorized access, universal use, limited scale, minimal training, rapid setup, rapid authentication, low error rates, and high memorability. The proposed haptic authentication meets many of these requirements, particularly security, universal use, limited scale, minimal training, low error rates, and high memorability. The proposed system, however, could not meet an important requirement in terms of rapid authentication, and needs to be improved. The suggested system was made to be simple, using a personal ID tag as a portable accessory that is omnipresent in today's corporate environment, so that the actions of manipulating the device make the recognition and classification processes easier and seamless. Therefore, inconvenient authentication processes of explicitly scanning a personal object or typing in a personal password can be removed [27]. In addition, since the accelerator sensor is relatively cheap, although it requires additional battery

Figure 5: Success rates for copying haptic passcodes of various digit lengths. support, the cost to set up the required infrastructure to support an authentication system can be minimized using the suggested authentication system. ### Mobile Application

The same haptic authentication algorithm can be applied to personal devices such as smartphones which are equipped with a built-in acceleration sensor. With the widespread use of acceleration sensors these days, a mobile phone may be a good alternative to a traditional ID tag in terms of security [27]. We briefly tested the same authentication system on a mobile phone (Galaxy Note 8 model by Samsung (Seoul, Korea) with 6.3 inch display, 2960 \(\times\) 1440 resolution) to test system validity with the same participants who engaged in the copying attack experiment. Just like in the ID tag cases, the haptic manipulation for the VF180 (vertical flip of 180 degrees) gesture was difficult to make with a mobile phone. Manipulation of a mobile phone with the required haptic movement needs one hand to firmly grab the phone, not like when an ID tag is hung on the neck, with the other hand to tap, flip, and shake. Since manipulation of a mobile phone was much more difficult to do than that of an ID tag, VF90 and VF180 needed to be replaced with VF45 (for 45 degrees) and VF90, respectively, to enhance the accuracy. Even though the signals were different from those from an ID tag in form and duration, the same algorithm could still be applied to classify the haptic gestures. Many smartphones today are embedded with an acceleration sensor and durable battery for a variety of functions. Smartphones seem to be a good candidate for a functional device to be used as a personal tool for authentication process. It has been proved that discrete gesture patterns are hard for users to retain [12], and attackers would have a hard time distinguishing and memorizing another user's haptic manipulations of their phone. Since the haptic manipulations of a phone look very similar to each other, they are difficult for attackers to figure out and to reconstruct. People with physical disabilities who cannot make precise manual inputs into mobile phones due to the small keypad can take advantage of the simple haptic manipulations to enter a personal passcode with the proposed system, even though they may need much longer to make a passcode. ### Future Studies

We previously demonstrated the possibility and usability of ID tags in interaction with computerized systems [27; 28; 29]. The following problems for the proposed authentication scheme using an ID tag need to be solved in order for it to be an effective and efficient authentication system in real practices. First, controlling the battery power more efficiently for the ID tag needs to be resolved since the system cannot be powered on all the time. It would be a much more efficient system if the power turns on only when the authentication process is to be started [28; 29].