IEICE Transactions on Information and Systems
Online ISSN : 1745-1361
Print ISSN : 0916-8532
Volume E103.D, Issue 7
Displaying 1-31 of 31 articles from this issue
Special Section on Information and Communication System Security
• Kazuomi OISHI
2020 Volume E103.D Issue 7 Pages 1431-1432
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS
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• Kwangjo KIM
Article type: INVITED PAPER
2020 Volume E103.D Issue 7 Pages 1433-1447
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

Deep learning is gaining more and more lots of attractions and better performance in implementing the Intrusion Detection System (IDS), especially for feature learning. This paper presents the state-of-the-art advances and challenges in IDS using deep learning models, which have been achieved the big performance enhancements in the field of computer vision, natural language processing, and image/audio processing than the traditional methods. After providing a systematic and methodical description of the latest developments in deep learning from the points of the deployed architectures and techniques, we suggest the pros-and-cons of all the deep learning-based IDS, and discuss the importance of deep learning models as feature learning approach. For this, the author has suggested the concept of the Deep-Feature Extraction and Selection (D-FES). By combining the stacked feature extraction and the weighted feature selection for D-FES, our experiment was verified to get the best performance of detection rate, 99.918% and false alarm rate, 0.012% to detect the impersonation attacks in Wi-Fi network which can be achieved better than the previous publications. Summary and further challenges are suggested as a concluding remark.

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• Heung Youl YOUM
Article type: INVITED PAPER
2020 Volume E103.D Issue 7 Pages 1448-1461
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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De-identification[1]-[5], [30]-[71] is the process that organizations can use to remove personal information from data that they collect, use, archive, and share with other organizations. It is recognized as an important tool for organizations to balance requirements between the use of data and privacy protection of personal information. Its objective is to remove the association between a set of identifying attributes and the data principal where identifying attribute is attribute in a dataset that is able to contribute to uniquely identifying a data principal within a specific operational context and data principal is entity to which data relates. This paper provides an overview of de-identification techniques including the data release models. It also describes the current standardization activities by the standardization development organizations in terms of de-identification. It suggests future standardization directions including potential future work items.

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• Hiroki KUZUNO, Toshihiro YAMAUCHI
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1462-1475
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Countermeasures against attacks targeting an operating system are highly effective in preventing security compromises caused by kernel vulnerability. An adversary uses such attacks to overwrite credential information, thereby overcoming security features through arbitrary program execution. CPU features such as Supervisor Mode Access Prevention, Supervisor Mode Execution Prevention and the No eXecute bit facilitate access permission control and data execution in virtual memory. Additionally, Linux reduces actual attacks through kernel vulnerability affects via several protection methods including Kernel Address Space Layout Randomization, Control Flow Integrity, and Kernel Page Table Isolation. Although the combination of these methods can mitigate attacks as kernel vulnerability relies on the interaction between the user and the kernel modes, kernel virtual memory corruption can still occur (e.g., the eBPF vulnerability allows malicious memory overwriting only in the kernel mode). We present the Kernel Memory Observer (KMO), which has a secret observation mechanism to monitor kernel virtual memory. KMO is an alternative design for virtual memory can detect illegal data manipulation/writing in the kernel virtual memory. KMO determines kernel virtual memory corruption, inspects system call arguments, and forcibly unmaps the direct mapping area. An evaluation of KMO reveals that it can detect kernel virtual memory corruption that contains the defeating security feature through actual kernel vulnerabilities. In addition, the results indicate that the system call overhead latency ranges from 0.002 µs to 8.246 µs, and the web application benchmark ranges from 39.70 µs to 390.52 µs for each HTTP access, whereas KMO reduces these overheads by using tag-based Translation Lookaside Buffers.

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• Toshinori USUI, Tomonori IKUSE, Yuto OTSUKI, Yuhei KAWAKOYA, Makoto IW ...
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1476-1492
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Return-oriented programming (ROP) has been crucial for attackers to evade the security mechanisms of recent operating systems. Although existing ROP detection approaches mainly focus on host-based intrusion detection systems (HIDSes), network-based intrusion detection systems (NIDSes) are also desired to protect various hosts including IoT devices on the network. However, existing approaches are not enough for network-level protection due to two problems: (1) Dynamic approaches take the time with second- or minute-order on average for inspection. For applying to NIDSes, millisecond-order is required to achieve near real time detection. (2) Static approaches generate false positives because they use heuristic patterns. For applying to NIDSes, false positives should be minimized to suppress false alarms. In this paper, we propose a method for statically detecting ROP chains in malicious data by learning the target libraries (i.e., the libraries that are used for ROP gadgets). Our method accelerates its inspection by exhaustively collecting feasible ROP gadgets in the target libraries and learning them separated from the inspection step. In addition, we reduce false positives inevitable for existing static inspection by statically verifying whether a suspicious byte sequence can link properly when they are executed as a ROP chain. Experimental results showed that our method has achieved millisecond-order ROP chain detection with high precision.

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• Daiki CHIBA, Ayako AKIYAMA HASEGAWA, Takashi KOIDE, Yuta SAWABE, Shige ...
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1493-1511
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

Internationalized domain names (IDNs) are abused to create domain names that are visually similar to those of legitimate/popular brands. In this work, we systematize such domain names, which we call deceptive IDNs, and analyze the risks associated with them. In particular, we propose a new system called DomainScouter to detect various deceptive IDNs and calculate a deceptive IDN score, a new metric indicating the number of users that are likely to be misled by a deceptive IDN. We perform a comprehensive measurement study on the identified deceptive IDNs using over 4.4 million registered IDNs under 570 top-level domains (TLDs). The measurement results demonstrate that there are many previously unexplored deceptive IDNs targeting non-English brands or combining other domain squatting methods. Furthermore, we conduct online surveys to examine and highlight vulnerabilities in user perceptions when encountering such IDNs. Finally, we discuss the practical countermeasures that stakeholders can take against deceptive IDNs.

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• Fumihiro KANEI, Daiki CHIBA, Kunio HATO, Katsunari YOSHIOKA, Tsutomu M ...
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1512-1523
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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While the online advertisement is widely used on the web and on mobile applications, the monetary damages by advertising frauds (ad frauds) have become a severe problem. Countermeasures against ad frauds are evaded since they rely on noticeable features (e.g., burstiness of ad requests) that attackers can easily change. We propose an ad-fraud-detection method that leverages robust features against attacker evasion. We designed novel features on the basis of the statistics observed in an ad network calculated from a large amount of ad requests from legitimate users, such as the popularity of publisher websites and the tendencies of client environments. We assume that attackers cannot know of or manipulate these statistics and that features extracted from fraudulent ad requests tend to be outliers. These features are used to construct a machine-learning model for detecting fraudulent ad requests. We evaluated our proposed method by using ad-request logs observed within an actual ad network. The results revealed that our designed features improved the recall rate by 10% and had about 100,000-160,000 fewer false negatives per day than conventional features based on the burstiness of ad requests. In addition, by evaluating detection performance with long-term dataset, we confirmed that the proposed method is robust against performance degradation over time. Finally, we applied our proposed method to a large dataset constructed on an ad network and found several characteristics of the latest ad frauds in the wild, for example, a large amount of fraudulent ad requests is sent from cloud servers.

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• Asuka NAKAJIMA, Takuya WATANABE, Eitaro SHIOJI, Mitsuaki AKIYAMA, Mave ...
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1524-1540
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

With our ever increasing dependence on computers, many governments around the world have started to investigate strengthening the regulations on vulnerabilities and their lifecycle management. Although many previous works have studied this problem space for mainstream software packages and web applications, relatively few have studied this for consumer IoT devices. As our first step towards filling this void, this paper presents a pilot study on the vulnerability disclosures and patch releases of three prominent consumer IoT vendors in Japan and three in the United States. Our goals include (i) characterizing the trends and risks in the vulnerability lifecycle management of consumer IoT devices using accurate long-term data, and (ii) identifying problems, challenges, and potential approaches for future studies of this problem space. To this end, we collected all published vulnerabilities and patches related to the consumer IoT products by the included vendors between 2006 and 2017; then, we analyzed our dataset from multiple perspectives, such as the severity of the included vulnerabilities and the timing of the included patch releases with respect to the corresponding disclosures and exploits. Our work has uncovered several important findings that may inform future studies. These findings include (i) a stark contrast between how the vulnerabilities in our dataset were disclosed in the two markets, (ii) three alarming practices by the included vendors that may significantly increase the risk of 1-day exploits for customers, and (iii) challenges in data collection including crawling automation and long-term data availability. For each finding, we also provide discussions on its consequences and/or potential migrations or suggestions.

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• Keika MORI, Takuya WATANABE, Yunao ZHOU, Ayako AKIYAMA HASEGAWA, Mitsu ...
Article type: PAPER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1541-1555
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

This work aims to determine the propensity of password creation through the lens of language spheres. To this end, we consider four different countries, each with a different culture/language: China/Chinese, United Kingdom (UK) and India/English, and Japan/Japanese. We first employ a user study to verify whether language and culture are reflected in password creation. We found that users in India, Japan, and the UK prefer to create their passwords from base words, and the kinds of words they are incorporated into passwords vary between countries. We then test whether the findings obtained through the user study are reflected in a corpus of leaked passwords. We found that users in China and Japan prefer dates, while users in India, Japan, and the UK prefer names. We also found that cultural words (e.g., “sakura” in Japan and “football” in the UK) are frequently used to create passwords. Finally, we demonstrate that the knowledge on the linguistic background of targeted users can be exploited to increase the speed of the password guessing process.

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• Pratish DATTA, Tatsuaki OKAMOTO, Katsuyuki TAKASHIMA
Article type: PAPER
Subject area: Cryptographic Techniques
2020 Volume E103.D Issue 7 Pages 1556-1597
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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This paper demonstrates how to achieve simulation-based strong attribute hiding against adaptive adversaries for predicate encryption (PE) schemes supporting expressive predicate families under standard computational assumptions in bilinear groups. Our main result is a simulation-based adaptively strongly partially-hiding PE (PHPE) scheme for predicates computing arithmetic branching programs (ABP) on public attributes, followed by an inner-product predicate on private attributes. This simultaneously generalizes attribute-based encryption (ABE) for boolean formulas and ABP's as well as strongly attribute-hiding PE schemes for inner products. The proposed scheme is proven secure for any a priori bounded number of ciphertexts and an unbounded (polynomial) number of decryption keys, which is the best possible in the simulation-based adaptive security framework. This directly implies that our construction also achieves indistinguishability-based strongly partially-hiding security against adversaries requesting an unbounded (polynomial) number of ciphertexts and decryption keys. The security of the proposed scheme is derived under (asymmetric version of) the well-studied decisional linear (DLIN) assumption. Our work resolves an open problem posed by Wee in TCC 2017, where his result was limited to the semi-adaptive setting. Moreover, our result advances the current state of the art in both the fields of simulation-based and indistinguishability-based strongly attribute-hiding PE schemes. Our main technical contribution lies in extending the strong attribute hiding methodology of Okamoto and Takashima [EUROCRYPT 2012, ASIACRYPT 2012] to the framework of simulation-based security and beyond inner products.

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• Katsunari SHISHIDO, Atsuko MIYAJI
Article type: PAPER
Subject area: Cryptographic Techniques
2020 Volume E103.D Issue 7 Pages 1598-1607
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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In the age of information and communications technology (ICT), not only collecting data but also using such data is provided in various services. It is necessary to ensure data privacy in such services while providing efficient computation and communication complexity. In this paper, we propose the first interval test designed according to the notion of online and offline phases by executing our new empty-set check. Our protocol is proved to ensure both server and client privacy. Furthermore, neither the computational complexity of a client in the online phase nor the communicational complexity from a server to a client depends on the size of the set. As a result, even in a practical situation in which one server receives requests from numerous clients, the waiting time for a client to obtain the result of an interval test can be minimized.

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• Han-Yan WU, Ling-Hwei CHEN, Yu-Tai CHING
Article type: PAPER
Subject area: Cryptographic Techniques
2020 Volume E103.D Issue 7 Pages 1608-1617
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Embedding efficiency is an important issue in steganography methods. Matrix embedding (1, n, h) steganography was proposed by Crandall to achieve high embedding efficiency for palette images. This paper proposes a steganography method based on multilayer matrix embedding for palette images. First, a parity assignment is provided to increase the image quality. Then, a multilayer matrix embedding (k, 1, n, h) is presented to achieve high embedding efficiency and capacity. Without modifying the color palette, hk secret bits can be embedded into n pixels by changing at most k pixels. Under the same capacity, the embedding efficiency of the proposed method is compared with that of pixel-based steganography methods. The comparison indicates that the proposed method has higher embedding efficiency than pixel-based steganography methods. The experimental results also suggest that the proposed method provides higher image quality than some existing methods under the same embedding efficiency and capacity.

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• Kento HASEGAWA, Masao YANAGISAWA, Nozomu TOGAWA
Article type: LETTER
Subject area: Network and System Security
2020 Volume E103.D Issue 7 Pages 1618-1622
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Cybersecurity has become a serious concern in our daily lives. The malicious functions inserted into hardware devices have been well known as hardware Trojans. In this letter, we propose a hardware-Trojan classification method at gate-level netlists utilizing boundary net structures. We first use a machine-learning-based hardware-Trojan detection method and classify the nets in a given netlist into a set of normal nets and a set of Trojan nets. Based on the classification results, we investigate the net structures around the boundary between normal nets and Trojan nets, and extract the features of the nets mistakenly identified to be normal nets or Trojan nets. Finally, based on the extracted features of the boundary nets, we again classify the nets in a given netlist into a set of normal nets and a set of Trojan nets. The experimental results demonstrate that our proposed method outperforms an existing machine-learning-based hardware-Trojan detection method in terms of its true positive rate.

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Regular Section
• Kokoro KOBAYASHI, Tsuyoshi OGUNI, Masaki NAKAGAWA
Article type: PAPER
Subject area: Computer System
2020 Volume E103.D Issue 7 Pages 1623-1632
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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This paper presents a series of secure PIN/password input methods resilient to shoulder hacking. When a person inputs a PIN or password to a smartphone, tablet, banking terminal, etc., there is a risk of shoulder hacking of the PIN or the password being stolen. To decrease the risk, we propose a method that erases key-top labels, moves them smoothly and simultaneously, and lets the user touch the target key after they stopped. The user only needs to trace a single key, but peepers have to trace the movements of all the keys at the same time. We extend the method by assigning different colors, shapes, and/or sizes to keys for enhancing distinguishability, which allows all the keys to be moved instantaneously after key-top labels are erased and the user to touch the target key. We also introduce a “move backward/forward” function that allows the user to play back the movements. This series of methods does not have the highest security, but it is easy to use and does not require any changes to the server side. Results of a performance evaluation demonstrate that this method has high resistance to shoulder hacking while providing satisfactory usability without large input errors.

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• Takafumi KUBOTA, Naohiro AOTA, Kenji KONO
Article type: PAPER
Subject area: Software System
2020 Volume E103.D Issue 7 Pages 1633-1646
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Logging is a practical and useful way of diagnosing failures in software systems. The logged events are crucially important to learning what happened during a failure. If key events are not logged, it is almost impossible to track error propagations in the diagnosis. Tracking an error propagation becomes utterly complicated if inter-thread data dependency is involved. An inter-thread data dependency arises when one thread accesses to share data corrupted by another thread. Since the erroneous state propagates from a buggy thread to a failing thread through the corrupt shared data, the root cause cannot be tracked back solely by investigating the failing thread. This paper presents the design and implementation of K9, a tool that inserts logging code automatically to trace inter-thread data dependencies. K9 is designed to be “practical”; it scales to one million lines of code in C, causes negligible runtime overheads, and provides clues to tracking inter-thread dependencies in real-world bugs. To scale to one million lines of code, K9 ditches rigorous static analysis of pointers to detect code locations where inter-thread data dependency can occur. Instead, K9 takes the best-effort approach and finds out “most” of those code locations by making use of coding conventions. This paper demonstrates that K9 is applicable to Linux and captures relevant code locations, in spite of the best-effort approach, enough to provide useful clues to root causes in real-world bugs, including a previously unknown bug in Linux. The paper also shows K9 runtime overhead is negligible. K9 incurs 1.25% throughput degradation and 0.18% CPU usage increase, on average, in our evaluation.

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• Sanghun CHOI, Shuichiro HARUTA, Yichen AN, Iwao SASASE
Article type: PAPER
Subject area: Data Engineering, Web Information Systems
2020 Volume E103.D Issue 7 Pages 1647-1659
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Since the owner's data might be leaked from the centralized server storage, the distributed storage schemes with the server storage have been investigated. To ensure the owner's data in those schemes, they use Reed Solomon code. However, those schemes occur the burden of data capacity since the parity data are increased by how much the disconnected data can be restored. Moreover, the calculation time for the restoration will be higher since many parity data are needed to restore the disconnected data. In order to reduce the burden of data capacity and the calculation time, we proposed the server-based distributed storage using Secret Sharing with AES-256 for lightweight safety restoration. Although we use Secret Sharing, the owner's data will be safely kept in the distributed storage since all of the divided data are divided into two pieces with the AES-256 and stored in the peer storage and the server storage. Even though the server storage keeps the divided data, the server and the peer storages might know the pair of divided data via Secret Sharing, the owner's data are secure in the proposed scheme from the inner attack of Secret Sharing. Furthermore, the owner's data can be restored by a few parity data. The evaluations show that our proposed scheme is improved for lightweight, stability, and safety.

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• Kenta ISHIGURO, Kenji KONO
Article type: PAPER
Subject area: Dependable Computing
2020 Volume E103.D Issue 7 Pages 1660-1671
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Vulnerabilities in hypervisors are crucial in multi-tenant clouds and attractive for attackers because a vulnerability in the hypervisor can undermine all the virtual machine (VM) security. This paper focuses on vulnerabilities in instruction emulators inside hypervisors. Vulnerabilities in instruction emulators are not rare; CVE-2017-2583, CVE-2016-9756, CVE-2015-0239, CVE-2014-3647, to name a few. For backward compatibility with legacy x86 CPUs, conventional hypervisors emulate arbitrary instructions at any time if requested. This design leads to a large attack surface, making it hard to get rid of vulnerabilities in the emulator.

This paper proposes FWinst that narrows the attack surface against vulnerabilities in the emulator. The key insight behind FWinst is that the emulator should emulate only a small subset of instructions, depending on the underlying CPU micro-architecture and the hypervisor configuration. FWinst recognizes emulation contexts in which the instruction emulator is invoked, and identifies a legitimate subset of instructions that are allowed to be emulated in the current context. By filtering out illegitimate instructions, FWinst narrows the attack surface. In particular, FWinst is effective on recent x86 micro-architectures because the legitimate subset becomes very small. Our experimental results demonstrate FWinst prevents existing vulnerabilities in the emulator from being exploited on Westmere and Skylake micro-architectures, and the runtime overhead is negligible.

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• Masashi TSUCHIDA, Fukuhito OOSHITA, Michiko INOUE
Article type: PAPER
Subject area: Dependable Computing
2020 Volume E103.D Issue 7 Pages 1672-1682
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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We propose two algorithms for the gathering of k mobile agents in asynchronous Byzantine environments. For both algorithms, we assume that graph topology is arbitrary, each node is equipped with an authenticated whiteboard, agents have unique IDs, and at most f weakly Byzantine agents exist. Here, a weakly Byzantine agent can make arbitrary behavior except falsifying its ID. Under these assumptions, the first algorithm achieves a gathering without termination detection in O(m+fn) moves per agent (m is the number of edges and n is the number of nodes). The second algorithm achieves a gathering with termination detection in O(m+fn) moves per agent by additionally assuming that agents on the same node are synchronized, $f<\lceil \frac{1}{3} k \rceil$ holds, and agents know k. To the best of our knowledge, this is the first work to address the gathering problem of mobile agents for arbitrary topology networks in asynchronous Byzantine environments.

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• Taewhan KIM, Kangsoo JUNG, Seog PARK
Article type: PAPER
Subject area: Artificial Intelligence, Data Mining
2020 Volume E103.D Issue 7 Pages 1683-1692
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Web service users are overwhelmed by the amount of information presented to them and have difficulties in finding the information that they need. Therefore, a recommendation system that predicts users' taste is an essential factor for the success of businesses. However, recommendation systems require users' personal information and can thus lead to serious privacy violations. To solve this problem, many research has been conducted about protecting personal information in recommendation systems and implementing differential privacy, a privacy protection technique that inserts noise into the original data. However, previous studies did not examine the following factors in applying differential privacy to recommendation systems. First, they did not consider the sparsity of user rating information. The total number of items is much more than the number of user-rated items. Therefore, a rating matrix created for users and items will be very sparse. This characteristic renders the identification of user patterns in rating matrixes difficult. Therefore, the sparsity issue should be considered in the application of differential privacy to recommendation systems. Second, previous studies focused on protecting user rating information but did not aim to protect the lists of user-rated items. Recommendation systems should protect these item lists because they also disclose user preferences. In this study, we propose a differentially private recommendation scheme that bases on a grouping method to solve the sparsity issue and to protect user-rated item lists and user rating information. The proposed technique shows better performance and privacy protection on actual movie rating data in comparison with an existing technique.

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• Kota KUDO, Yuichi TAKANO, Ryo NOMURA
Article type: PAPER
Subject area: Artificial Intelligence, Data Mining
2020 Volume E103.D Issue 7 Pages 1693-1702
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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This paper addresses the problem of selecting a significant subset of candidate features to use for multiple linear regression. Bertsimas et al. [5] recently proposed the discrete first-order (DFO) algorithm to efficiently find near-optimal solutions to this problem. However, this algorithm is unable to escape from locally optimal solutions. To resolve this, we propose a stochastic discrete first-order (SDFO) algorithm for feature subset selection. In this algorithm, random perturbations are added to a sequence of candidate solutions as a means to escape from locally optimal solutions, which broadens the range of discoverable solutions. Moreover, we derive the optimal step size in the gradient-descent direction to accelerate convergence of the algorithm. We also make effective use of the L2-regularization term to improve the predictive performance of a resultant subset regression model. The simulation results demonstrate that our algorithm substantially outperforms the original DFO algorithm. Our algorithm was superior in predictive performance to lasso and forward stepwise selection as well.

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• Yizhong XIN, Ruonan LIU, Yan LI
Article type: PAPER
Subject area: Human-computer Interaction
2020 Volume E103.D Issue 7 Pages 1703-1709
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Aiming at the problem of low accuracy of target selection in indirect touch input, an indirect multi-touch input device was designed and built. We explored here four indirect touch input techniques which were TarConstant, TarEnlarge, TarAttract, TarEnlargeAttract, and investigated their performance when subjects completing the target selection tasks through comparative experiments. Results showed that TarEnlargeAttract enabled the shortest movement time along with the lowest error rate, 2349.9ms and 10.9% respectively. In terms of learning effect, both TarAttract and TarEnlargeAttract had learning effect on movement time, which indicated that the speed of these two techniques can be improved with training. Finally, the strategy of improving the accuracy of indirect touch input was given, which has reference significance for the interface design of indirect touch input.

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• Ayumi YAMAZAKI, Yuki HAYASHI, Kazuhisa SETA
Article type: PAPER
Subject area: Educational Technology
2020 Volume E103.D Issue 7 Pages 1710-1721
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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When moving through space, we have to consider the route to the destination and gather real-world information to check that we are following this route correctly. In this study, we define spatial movement skill as this ability to associate information like maps and memory with real-world objects like signs and buildings. Without adequate spatial movement skills, people are liable to experience difficulties such as going around in circles and getting lost. Alleviating this problem requires better spatial movement skills, but few studies have considered how this can be achieved or supported, and we have found no research into how the improvement of these skills can be supported in practice. Since spatial cognition is always necessary for spatial movement, our aim in this study is to develop a spatial movement skill training system. To this end, we first overviewed the use of knowledge gained from the research literature on spatial cognition. From these related studies, we systematically summarized issues and challenges related to spatial movement and the stages of spatial information processing, and created a new learning model for the improvement of spatial movement skills. Then, based on this model, we developed a system that uses position information to support the improvement of spatial movement skills. Initial experiments with this system confirmed that its use promotes recognition from a global viewpoint to the current location and direction, resulting in the formation of a cognitive map, which suggests that it has an effect on spatial movement skills.

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• Lia SADITA, Pedro Gabriel Fonteles FURTADO, Tsukasa HIRASHIMA, Yusuke ...
Article type: PAPER
Subject area: Educational Technology
2020 Volume E103.D Issue 7 Pages 1722-1731
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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Concept mapping is one of the instructional strategies implemented in collaborative learning to support discourse and learning. While prior studies have established its positive significance on the learning achievements and attitudes of students, they have also discovered that it can lead to students conducting less discussion on conceptual knowledge compared to procedural and team coordination. For instance, some inaccurate ideas are never challenged and can become ingrained. Designing a learning environment where individual knowledge is acknowledged and developed constructively is necessary to achieve similarity of individual knowledge after collaboration. This study applies the Reciprocal Kit Build (RKB) approach before collaborative concept mapping. The approach consists of three main phases: (1) individual map construction; (2) re-constructional map building; and (3) difference map discussion. Finally, each team will build a group map. Previous studies have shown that the visualization of similarities and differences during the third phase correlates with the improvement of concept map quality. The current paper presents our investigation on the effects of the first and second phases in terms of the final group products. We analyze the correlations between the similarity of individual knowledge represented in the first-phase maps, the comprehension of partner's representation during the second phase, and the changes of map scores. Our findings indicate that comprehension level is a stronger predictor than the similarity of individual knowledge for estimating score gain. The ways in which patterns of knowledge transfer from individual to group maps, which exhibit how the group products are built based on individual inputs, are also discussed. We illustrate that the number of shared and unshared links in the group solutions are proportionally distributed, and that the number of reconstructed links dominates the group solutions, rather than the non-reconstructed ones.

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• Lu YIN, Junfeng LI, Yonghong YAN, Masato AKAGI
Article type: PAPER
Subject area: Speech and Hearing
2020 Volume E103.D Issue 7 Pages 1732-1743
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
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The simultaneous utterances impact the ability of both the hearing-impaired persons and automatic speech recognition systems. Recently, deep neural networks have dramatically improved the speech separation performance. However, most previous works only estimate the speech magnitude and use the mixture phase for speech reconstruction. The use of the mixture phase has become a critical limitation for separation performance. This study proposes a two-stage phase-aware approach for multi-talker speech separation, which integrally recovers the magnitude as well as the phase. For the phase recovery, Multiple Input Spectrogram Inversion (MISI) algorithm is utilized due to its effectiveness and simplicity. The study implements the MISI algorithm based on the mask and gives that the ideal amplitude mask (IAM) is the optimal mask for the mask-based MISI phase recovery, which brings less phase distortion. To compensate for the error of phase recovery and minimize the signal distortion, an advanced mask is proposed for the magnitude estimation. The IAM and the proposed mask are estimated at different stages to recover the phase and the magnitude, respectively. Two frameworks of neural network are evaluated for the magnitude estimation on the second stage, demonstrating the effectiveness and flexibility of the proposed approach. The experimental results demonstrate that the proposed approach significantly minimizes the distortions of the separated speech.

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• Yun HU, Changwen ZHENG
Article type: PAPER
Subject area: Natural Language Processing
2020 Volume E103.D Issue 7 Pages 1744-1752
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

Named Entity Recognition (NER) systems are often realized by supervised methods such as CRF and neural network methods, which require large annotated data. In some domains that small annotated training data is available, multi-domain or multi-task learning methods are often used. In this paper, we explore the methods that use news domain and Chinese Word Segmentation (CWS) task to improve the performance of Chinese named entity recognition in weibo domain. We first propose two baseline models combining multi-domain and multi-task information. The two baseline models share information between different domains and tasks through sharing parameters simply. Then, we propose a Double ADVersarial model (DoubADV model). The model uses two adversarial networks considering the shared and private features in different domains and tasks. Experimental results show that our DoubADV model outperforms other baseline models and achieves state-of-the-art performance compared with previous works in multi-domain and multi-task situation.

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• Keiichiro INAGAKI, Takayuki KANNON, Yoshimi KAMIYAMA, Shiro USUI
Article type: PAPER
Subject area: Biological Engineering
2020 Volume E103.D Issue 7 Pages 1753-1759
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

The eyes are continuously fluctuating during fixation. These fluctuations are called fixational eye movements. Fixational eye movements consist of tremors, microsaccades, and ocular drifts. Fixational eye movements aid our vision by shaping spatial-temporal characteristics. Here, it is known that photoreceptors, the first input layer of the retinal network, have a spatially non-uniform cell alignment called the cone mosaic. The roles of fixational eye movements are being gradually uncovered; however, the effects of the cone mosaic are not considered. Here we constructed a large-scale visual system model to explore the effect of the cone mosaic on the visual signal processing associated with fixational eye movements. The visual system model consisted of a brainstem, eye optics, and photoreceptors. In the simulation, we focused on the roles of fixational eye movements on signal processing with sparse sampling by photoreceptors given their spatially non-uniform mosaic. To analyze quantitatively the effect of fixational eye movements, the capacity of information processing in the simulated photoreceptor responses was evaluated by information rate. We confirmed that the information rate by sparse sampling due to the cone mosaic was increased with fixational eye movements. We also confirmed that the increase of the information rate was derived from the increase of the responses for the edges of objects. These results suggest that visual information is already enhanced at the level of the photoreceptors by fixational eye movements.

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• Yong YANG, Junwei LU, Baoxian WANG, Weigang ZHAO
Article type: LETTER
Subject area: Fundamentals of Information Systems
2020 Volume E103.D Issue 7 Pages 1760-1764
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

The concrete quality of supporting layer in ballastless track is important for the safe operation of a high-speed railway (HSR). However, the supporting layer is covered by the upper track slab and the functional layer, and it is difficult to detect concealed defects inside the supporting layer. To solve this problem, a method of elastic wave velocity imaging is proposed to analyze the concrete quality. First, the propagation path of the elastic wave in the supporting layer is analyzed, and a head-wave arrival-time (HWAT) extraction method based on the wavelet spectrum correlation analysis (WSCA) is proposed. Then, a grid model is established to analyze the relationships among the grid wave velocity, travel route, and travel time. A loss function based on the total variation is constructed, and an inverse method is applied to evaluate the elastic wave velocity in the supporting layer. Finally, simulation and field experiments are conducted to verify the suppression of noise signals and the accuracy of an inverse imaging for the elastic wave velocity estimation. The results show that the WSCA analysis could extract the HWAT efficiently, and the inverse imaging method could accurately estimate wave velocity in the supporting layer.

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• Jingyu LI, Dandan XIAO, Yue ZHANG
Article type: LETTER
Subject area: Computer System
2020 Volume E103.D Issue 7 Pages 1765-1768
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

A high-speed high-resolution sampling system is the crucial part in wideband radar receivers. A 10.4-GS/s 12-bit wideband sampling system based on TIADC technique is designed in this letter. The acquisition function is implemented on a VPX platform. The storage function is implemented on a standard 19-inch rack server. The sampled data is transmitted at high speed through optical fibers between them. A mixed calibration method based on perfect reconstruction is adopted to compensate channel mismatches of wideband TIADC system. For sinusoidal signals from 100MHz to 5000MHz, more than 46-dB SNDR and 56-dB SFDR can be obtained in this sampling system. This letter provides a high-speed and high-resolution acquisition scheme for direct intermediate frequency sampling wideband digital receivers.

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• Hae Young LEE, Jin Myoung KIM
Article type: LETTER
Subject area: Software System
2020 Volume E103.D Issue 7 Pages 1769-1772
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

In this letter, we propose a more secure modeling and simulation approach that can systematically detect state variable corruptions caused by buffer overflows in simulation models. Using our approach, developers may not consider secure coding practices related to the corruptions. We have implemented a prototype of the approach based on a modeling and simulation formalism and an open source simulator. Through optimization, the prototype could show better performance, compared to the original simulator, and detect state variable corruptions.

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• He LI, YanNa LIU, XuHua WANG, LiangCai SU, Hang YUAN, JaeSoo YOO
Article type: LETTER
Subject area: Data Engineering, Web Information Systems
2020 Volume E103.D Issue 7 Pages 1773-1776
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

Due to most of the existing graph repartitioning methods are known for poor efficiency in distributed environments. In this paper, we introduce a new graph repartitioning method with two phases in distributed environments. In the first phase, a local method is designed to identify all the potential candidate vertices that should be moved to the other partitions at once in each partition locally. In the second phase, a streaming graph processing model is adopted to reassign the candidate vertices to achieve lightweight graph repartitioning. During the reassignment of the vertex, we propose an objective function to balance both the load balance and the number of crossing edges among the distributed partitions. The experimental results with a large set of real word and synthetic graph datasets show that the communication cost can be reduced by nearly 1 to 2 orders of magnitude compared with the existing methods.

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• Minseong KIM, Hyun-Chul CHOI
Article type: LETTER
Subject area: Pattern Recognition
2020 Volume E103.D Issue 7 Pages 1777-1781
Published: July 01, 2020
Released on J-STAGE: July 01, 2020
JOURNAL FREE ACCESS

Faster R-CNN uses a region proposal network which consists of a single scale convolution filter and fully connected networks to localize detected regions. However, using a single scale filter is not enough to detect full regions of characters. In this letter, we propose a simple but effective way, i.e., utilizing variously sized convolution filters, to accurately detect Chinese characters of multiple scales in documents. We experimentally verified that our method improved IoU by 4% and detection rate by 3% than the previous single scale Faster R-CNN method.

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