Papers - USUZAKI SHOTARO
-
Shotaro Usuzaki, Kentaro Aburada, Hisaaki Yamaba, Mirang Park, Naonobu Okazaki
67 ( 3 ) 588 - 604 2026.3
Language：Japanese Publishing type：Research paper (scientific journal)
DOI： 10.20729/0002008648
-
Takatsuka Kayoko, Usuzaki Shotaro, Yamaba Hisaaki, Aburata Kentaro, Okazaki Naonobu
KAGAKU KOGAKU RONBUNSHU 52 ( 1 ) 15 - 20 2026.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Society of Chemical Engineers, Japan
The spread of infectious diseases in the livestock industry results in severe economic losses and social disruption. This study focuses on the 2010 outbreak of foot-and-mouth disease (FMD) in Miyazaki Prefecture, Japan, and proposes a framework for quantitatively assessing farm-level susceptibility to infection through the construction of a Potential Infection Risk Index (λ). This index integrates multiple factors, including spatial proximity between farms, herd size, and livestock species. Statistical analysis reveals that λ values significantly differ between infected and uninfected farms, with the disparity widening as distance from the infection source decreases. These findings indicate that the spread of infection is strongly influenced by both geographic proximity and structural characteristics of farms. Furthermore, λ enables objective and quantitative identification of high-risk farms, supporting practical responses such as the prioritized allocation of limited disease control resources and the flexible application of hygiene management standards. A case study simulating farm relocation demonstrates that λ-based site selection effectively reduces infection risk, thereby validating the index as a practical and economically rational decision-support indicator. This approach also suggests the potential application of λ in long-term farm siting and structural planning. Additionally, the study envisions a comprehensive disease control support system centered on λ and its adjusted form (λ′), incorporating features such as risk visualization, hygiene-related corrections, tailored alerts and recommendations, and integration with administrative decision-making processes. Future work will focus on the development and implementation of such decision-support tools, with the ultimate goal of enhancing disease control efforts and contributing to the sustainable development of the livestock industry.
-
Shotaro Usuzaki, Kosei Iwasa, Nobuya Takahashi, Kentaro Aburada, Hisaaki Yamaba, Mirang Park, Naonobu Okazaki
2025 9th International Conference on Information Technology (InCIT) 545 - 552 2025.11
Publishing type：Research paper (international conference proceedings) Publisher：IEEE
-
Conjugate Gradient Based Multiplicative Update Rules for Nonnegative Matrix Factorization Reviewed
Nobuya Takahashi, Shotaro Usuzaki, Tetsuro Katayama, Masahiro Yokomichi, Kentaro Aburada, Naonobu Okazaki
2025 9th International Conference on Information Technology (InCIT) 639 - 644 2025.11
Publishing type：Research paper (international conference proceedings) Publisher：IEEE
-
Evaluating the usability and security of the text-based CAPTCHA that asks to recognize hidden text with the help of human visual completion function Reviewed
Shotaro Usuzaki, Nobuya Takahashi, Taiki Kamada, Kentaro Aburada, Hisaaki Yamaba, Mirang Park, Naonobu Okazaki
IEICE COMMUNICATIONS EXPRESS 14 ( 12 ) 441 - 444 2025
Language：English Publishing type：Research paper (scientific journal)
-
Yamaba H., Komori N., Usuzaki S., Aburada K., Katayama T., Okazaki N.
Icce Taiwan 2025 12th IEEE International Conference on Consumer Electronics Taiwan Generative AI in Innovative Consumer Technology Proceedings 111 - 112 2025
Publishing type：Research paper (scientific journal) Publisher：Icce Taiwan 2025 12th IEEE International Conference on Consumer Electronics Taiwan Generative AI in Innovative Consumer Technology Proceedings
Mobile devices such as smartphones and tablets are now deeply integrated into daily life. To prevent shoulder surfing attacks, we propose a user authentication method for mobile devices based on surface electromyogram (s-EMG) signals. The method uses a “pass-gesture,” a sequence of hand gestures that can be changed like a password. Fingerspelling was adopted as the source of gesture candidates. Previous studies confirmed high accuracy in identifying gestures performed by the same subject. This paper focuses on evaluating subject specificity-specifically, confirming that a model trained on one user fails to recognize gestures performed by another. Experimental results show that the system does not generalize across users, indicating robustness against impersonation.
-
Okazaki N., Usuzaki S., Waki T., Kawagoe H., Park M., Yamaba H., Aburada K.
Future Internet 16 ( 8 ) 2024.8
Publishing type：Research paper (scientific journal) Publisher：Future Internet
We propose a detection system incorporating a weighted voting mechanism that reflects the vote’s reliability based on the accuracy of each detector’s examination, which overcomes the problem of cooperative detection. Collaborative malware detection is an effective strategy against zero-day attacks compared to one using only a single detector because the strategy might pick up attacks that a single detector overlooked. However, cooperative detection is still ineffective if most anti-virus engines lack sufficient intelligence to detect zero-day malware. Most collaborative methods rely on majority voting, which prioritizes the quantity of votes rather than the quality of those votes. Therefore, our study investigated the zero-day malware detection accuracy of the collaborative system that optimally rates their weight of votes based on their malware categories of expertise of each anti-virus engine. We implemented the prototype system with the VirusTotal API and evaluated the system using real malware registered in MalwareBazaar. To evaluate the effectiveness of zero-day malware detection, we measured recall using the inspection results on the same day the malware was registered in the MalwareBazaar repository. Through experiments, we confirmed that the proposed system can suppress the false negatives of uniformly weighted voting and improve detection accuracy against new types of malware.
DOI： 10.3390/fi16080259
-
Usability improvement in color constancy CAPTCHA Reviewed
Usuzaki, Shotaro, Yihan, Wang, Aburada, Kentaro, Yamaba, Hisaaki, Takatsuka, Kayoko, Katayama, Tetsuro, Park, Mirang, Okazaki, Naonobu
IEICE Communications Express 2024
Publishing type：Research paper (scientific journal)
-
Proposal of Fill in the Missing Letters CAPTCHA Using Associations from Images Reviewed
Yamaba H., Mustaza M.N.F.B., Usuzaki S., Aburada K., Mukunoki M., Park M., Okazaki N.
Lecture Notes in Electrical Engineering 1114 LNEE 206 - 217 2024
Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Electrical Engineering
This paper proposes a new fill in the missing letters type CAPTCHA using associations from images. Many web sites have adopted CAPTCHA to prevent bots and other automated programs from malicious activities such as posting comment spam. Text-based CAPTCHA is the most common and earliest CAPTCHA. But as optical character recognition (OCR) technology has improved, the intensity of distortions that must be applied to a CAPTCHA for it to remain unrecognizable by OCR has increased. This has reached a point where humans are having difficulty recognizing CAPTCHA text. The idea of the proposed CAPTCHA asks users to spell a word by filling some blanks. Since the number of shown letters are few, it is difficult to answer the correct word. But one or more images that can be used as hints to guess what is the answer word are also shown to the users. A series of experiments was carried out to evaluated the performance of the proposed CAPTCHA. First, a computer program was developed with various software languages for the usability evaluation. The system was used for the experiments to find the suitable parameters of the CAPTCHA such as numbers of letters that will be disclosed, position of disclosed letters. Next, security evaluation experiments were carried out using the system under the obtained parameters. The results of the experiments showed that the performance and limitation of the proposed CAPTCHA.
-
Study of an Image-Based CAPTCHA that is Resistant to Attacks Using Image Recognition Systems Reviewed
Nishikawa S., Usuzaki S., Aburada K., Yamaba H., Katayama T., Park M., Okazaki N.
Lecture Notes in Electrical Engineering 1114 LNEE 175 - 184 2024
Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Electrical Engineering
In today’s digital age, image-based CAPTCHAs are increasingly vulnerable to attacks using annotation services, which tag images and classify images according to their contents, or reverse image search services. To prevent such attacks, an image-based CAPTCHA was proposed that takes advantage of the fact that humans can correctly recognize images containing many discontinuous points, while existing image recognition systems misrecognize them. However, this CAPTCHA proved susceptible to attacks using noise reduction filters. The objective of the present study is to create a CAPTCHA using images that are resistant to such filters. Images used in the new CAPTCHA were realized by increasing the proportion of lines forming discontinuous surfaces in images. Experimental results demonstrated a human recognition rate of 95.8%, with the image recognition systems successfully identifying only one image overall. Moreover, when a noise reduction filter was applied, the recognition rate was lower than those reported in previous studies.
-
Proposal of a DDoS Attack Detection Method Using the Communication Interval Reviewed
Iwasa K., Usuzaki S., Aburada K., Yamaba H., Katayama T., Park M., Okazaki N.
Lecture Notes in Electrical Engineering 1114 LNEE 165 - 174 2024
Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Electrical Engineering
As the scale of Distributed Denial of Service (DDoS) attacks has been escalating in recent years, the need for real-time detection of attacks has increased. Existing intrusion detection systems (IDSs) perform detection with a fixed window size (assumed to be in hours). In previous research, attack detection was performed by preparing windows of multiple sizes, selecting the appropriate window based on the state of the data, and using features learned in advance for that window size. Although this method yielded a high DDoS attack detection rate of 98.30%, it exhibited a considerable false-positive rate of 7.37%. The proposed method measures the communication intervals of identical packets within the window, identified as attack-related in the previous survey, and classifies those packets with an average communication interval below a set threshold as attacks. The experiment resulted in a 50.2% decrease in the false-positive rate.
-
An Architecture of Network Intrusion Detection and Prevention Systems for More Seamless Deployments Reviewed
Usuzaki S., Saito R.
GCCE 2024 - 2024 IEEE 13th Global Conference on Consumer Electronics 396 - 397 2024
Publishing type：Research paper (scientific journal) Publisher：GCCE 2024 - 2024 IEEE 13th Global Conference on Consumer Electronics
Network intrusion detection and prevention systems (NIDPS) are vital in defending against malicious network traffic. However, NIDPS has drawbacks in inspecting the traffic. While our previous paper addressed the issue by real-time switching the traffic path to direct the traffic to NIDPS with ARP spoofing, this approach resulted in unreliable traffic capturing for inspecting it. Therefore, we propose a new NIDS deployment mechanism based on the client-server model instead of using the ARP protocol. In this architecture, the monitored hosts (clients) request NIDPS controllers (servers) to modify the ARP entry to direct the traffic path to NIDPS. We verified the proposed method's performance in a virtual network environment through an evaluation experiment and showed that it could switch traffic in real time, just like the ARP Spoofing-based method.
-
Tsunami evacuation simulation considering road width in Aoshima district Reviewed
Nabeyama K., Usuzaki S., Aburada K., Yamaba H., Katayama T., Okazaki N.
Artificial Life and Robotics 28 ( 4 ) 779 - 788 2023.11
Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
Japan is one of the countries in the world where natural disasters occur most frequently. Typhoons, earthquakes, tsunamis, volcanic eruptions, and many other natural disasters occur in Japan every year, and the risks are immeasurable. Japan is especially prone to earthquakes because of its location on the North American Plate, Eurasian Plate, Pacific Plate, and Philippine Sea Plate. Preparation for a Nankai Trough earthquake is one of the most important issues. A Nankai trough earthquake is predicted to occur with a probability of 70–80% within 30 years. Accordingly, a tsunami of more than 10 ms is expected to hit a wide area along the Pacific coast from the Kanto region to the Kyushu region, and the impact is expected to be significant. When a tsunami warning is issued, an evacuation support system that provides information on evacuation sites and routes enables faster and safer evacuation actions. In a previous study conducted in our laboratory, we proposed an evacuation support system using Low-Power Wide-Area communications and conducted a simulation to find ways to improve the evacuation support system. However, the simulation was insufficient in that it did not consider delays in evacuation completion time due to road congestion caused by limited road width, which can be expected in an actual disaster. In our current research, as an improvement to make the simulation more realistic for further developing our evacuation support system, we propose a simulation that considers road width. We examined how adoption of this simulation methodology would affect the simulation results by comparing simulations that did and did not consider road width. As a result, the proposed method showed a lower percentage of completed evacuations than the previous simulation, especially for children and the elderly. The reason for this result is that when evacuations begin simultaneously, crowding occurs as people all rush to evacuation centers. This congestion on the roads near evacuation centers prevents people from completing their evacuations. Such a phenomenon is expected to occur not only in simulations but also on actual roads. For this reason, our proposed simulation method that considers road width is a more realistic simulation. Since evacuations by car in the event of a disaster also occur, a future issue is to simulate car congestion as well. Furthermore, simulating what would happen if a disaster made a road impassable is also important.
-
Proposal and evaluation for color constancy CAPTCHA Reviewed
Usuzaki S., Aburada K., Yamaba H., Katayama T., Mukunoki M., Park M., Okazaki N.
Artificial Life and Robotics 26 ( 3 ) 291 - 296 2021.8
Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
CAPTCHAs are technologies that distinguish humans and bot to prevent illegal access. Unfortunately, current CAPTCHAs, even the latest Google reCAPTCHA, have already broken with high accuracy. Although the devices, including emphasizing the distortion of the text and adding noise to the image, improve the machine resistance, they may decrease the accessibility of the web page. The purpose of this study is to propose a new CAPTCHA that can decrease the machine resistance while keeping usability. To achieve this purpose, we focused on color constancy. Color constancy is a human’s characteristic that enables humans to recognize the original color of the object by ignoring the effects of illumination light. Color constancy has not been fully reproduced by the program yet. We proposed color constancy CAPTCHA that the user is required to answer an original color of the object in a specified area on the CAPTCHA image with a color filter. In this paper, we created a prototype of CAPTCHA, applied two kinds of color filters, and then evaluated each case for the human success rate, machine success rate, and usability.
-
Proposal of Jawi CAPTCHA Using Digraphia Feature of the Malay Language Reviewed
Yamaba H., Sohaimi A.S.A.B.A., Usuzaki S., Aburada K., Mukunoki M., Park M., Okazaki N.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 12835 LNCS 119 - 133 2021
Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
This paper proposes a new text-based CAPTCHA using Jawi script and Latin script, which are both used in the Malay language writing system. Many web sites have adopted CAPTCHA to prevent bots and other automated programs from malicious activities such as posting comment spam. Text-based CAPTCHA is the most common and earliest CAPTCHA. But as optical character recognition (OCR) technology has improved, the intensity of distortions that must be applied to a CAPTCHA for it to remain unrecognizable by OCR has increased. This has reached a point where humans are having difficulty recognizing CAPTCHA text. The idea of the proposed CAPTCHA is to generate two identical character strings, one written in Latin script and the other in Jawi script. Because some of the strings characters are hidden by obstacles, users need to combine both strings to solve this CAPTCHA. This idea uses the fact that most Jawi characters have one-to-one correspondence with Latin characters. A series of experiments was carried out to evaluated the performance of the proposed CAPTCHA. First, a computer program was developed with various software languages for the usability evaluation. The results showed that the average time to solve the CAPTCHA and the accuracy rates were acceptable compared with the indices reported in existing research. Next, two OCR programs were applied to the Jawi CAPTCHA, and it was demonstrated that they could not read the partially hidden Latin and Jawi strings. Lastly, we discussed the effectiveness of the proposed CAPTCHA by relating to the priming effect.
-
Proposal and Evaluation of the Interactive Video CAPTCHA for Resistant to both Relay Attack and Automated Attack Reviewed
油田健太郎, 臼崎翔太郎, 山場久昭, 片山徹郎, 椋木雅之, PARK Mirang, 岡崎直宣
情報処理学会論文誌ジャーナル(Web) 62 ( 12 ) 2021
Publishing type：Research paper (scientific journal)
-
Blockchain-based malware detection method using shared signatures of suspected malware files Reviewed
Fuji R., Usuzaki S., Aburada K., Yamaba H., Katayama T., Park M., Shiratori N., Okazaki N.
Advances in Intelligent Systems and Computing 1036 305 - 316 2020
Publishing type：Research paper (scientific journal) Publisher：Advances in Intelligent Systems and Computing
Although rapid malware detection is very important, the detection is difficult due to the increase of new malware. In recent years, blockchain technology has attracted the attention of many people due to its four main characteristics of decentralization, persistency, anonymity, and auditability. In this paper, we propose a blockchain-based malware detection method that uses shared signatures of suspected malware files. The proposed method can share the signatures of suspected files between users, allowing them to rapidly respond to increasing malware threats. Further, it can improve the malware detection by utilizing signatures on the blockchain. In the evaluation experiment, we perform a more real simulation compared with our previous work to evaluate the detection accuracy. Compared with heuristic methods or behavior-based methods only, the proposed system which uses these methods plus signature-based method using shared signatures on the blockchain improved the false negative rate and the false positive rate.
-
On a user authentication method to realise an authentication system using s-EMG Reviewed
Yamaba H., Usuzaki S., Takatsuka K., Aburada K., Katayama T., Park M., Okazaki N.
International Journal of Grid and Utility Computing 11 ( 5 ) 725 - 734 2020
Publishing type：Research paper (scientific journal) Publisher：International Journal of Grid and Utility Computing
To prevent shoulder-surfing attacks, we proposed a user authentication method using surface electromyogram (s-EMG) signals, which can be used to identify who generated the signals and which gestures were made. Our method uses a technique called 'pass-gesture', which refers to a series of hand gestures, to achieve s-EMG-based authentication. However, it is necessary to introduce computer programs that can recognise gestures from the s-EMG signals. In this paper, we propose two methods that can be used to compare s-EMG signals and determine whether they were made by the same gesture. One uses support vector machines (SVMs), and the other uses dynamic time warping. We also introduced an appropriate method for selecting the validation data used to train SVMs using correlation coefficients and cross-correlation functions. A series of experiments was carried out to confirm the performance of those proposed methods, and the effectiveness of the two methods was confirmed.
-
Evaluation of Yubimoji Based Gestures for Realizing User Authentication Method Using s-EMG Reviewed
Yamaba H., Nagatomo Y., Usuzaki S., Takatsuka K., Aburada K., Katayama T., Park M., Okazaki N.
Advances in Intelligent Systems and Computing 1150 AISC 834 - 844 2020
Publishing type：Research paper (scientific journal) Publisher：Advances in Intelligent Systems and Computing
At the present time, since mobile devices such as tablet-type PCs and smart phones have penetrated deeply into our daily lives, an authentication method that prevents shoulder surfing attacks comes to be important. We are investigating a new user authentication method for mobile devices that uses surface electromyogram (s-EMG) signals, not screen touching. The s-EMG signals, which are generated by the electrical activity of muscle fibers during contraction, can be detected over the skin surface, and muscle movement can be differentiated by analyzing the s-EMG signals. Taking advantage of the characteristics, we proposed a method that uses a list of gestures as a password in the previous study. In order to realize this method, we have to prepare a sufficient number of gestures that are used to compose passwords. In this paper, we adopted fingerspelling as candidates of such gestures. We introduced manual kana of the Japanese Sign Language syllabary and selected the candidate gestures based on them. Their performances were evaluated by constructing their identifier using support vector machines.
-
Evaluation of manual alphabets based gestures for a user authentication method using s-emg Reviewed
Yamaba H., Usuzaki S., Takatsuka K., Aburada K., Katayama T., Park M., Okazaki N.
Advances in Intelligent Systems and Computing 1036 570 - 580 2020
Publishing type：Research paper (scientific journal) Publisher：Advances in Intelligent Systems and Computing
At the present time, since mobile devices such as tablet-type PCs and smart phones have widely penetrated into our daily lives, an authentication method that prevents shoulder surfing attacks comes to be important. We are investigating a new user authentication method for mobile devices that uses surface electromyogram (s-EMG) signals, not screen touching. The s-EMG signals, which are generated by the electrical activity of muscle fibers during contraction, can be detected over the skin surface, and muscle movement can be differentiated by analyzing the s-EMG signals. Taking advantage of the characteristics, we proposed a method that uses a list of gestures as a password in the previous study. In order to realize this method, we have to prepare a sufficient number of gestures that are used to compose passwords. In this paper, we adopted fingerspelling as candidates of such gestures. We measured s-EMG signals of manual kana of The Japanese Sign Language syllabary and evaluated their potential as the important element of the user authentication method.