• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.1-17
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• 2014

Cooperative spectrum sensing (CSS) is considered as a powerful approach to improve the utilization of scarce radio spectrum resources. However, most of CSS schemes assume all secondary users (SU) are honest, and thus offering opportunities for malicious SUs to launch the spectrum sensing data falsification attack (SSDF attack). To combat such misbehaved behaviors, recent efforts have been made to trust schemes. In this paper, we argue that powering CSS with traditional trust schemes is not enough. The rational SSDF attack is found in this paper. Unlike the simple SSDF attack, rational SSDF attackers send out false sensing data on a small number of interested primary users (PUs) rather than all PUs. In this case, rational SSDF attackers can keep up high trustworthiness, resulting in difficultly detecting malicious SUs in the traditional trust schemes. Meanwhile, a defense scheme using a novel trust approach is proposed to counter rational SSDF attack. Simulation results show that this scheme can successfully reduce the power of rational SSDF, and thus ensure the performance of CSS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4372-4394
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• 2020

The distribution of popular videos incurs a large amount of traffic at the base stations (BS) of networks. Device-to-multi-device (D2MD) communication has emerged an efficient radio access technology for offloading BS traffic in recent years. However, traditional studies have focused on synchronous user requests whereas asynchronous user requests are more common. Hence, offloading BS traffic in case of asynchronous user requests while considering their time-varying characteristics and the quality of experience (QoE) of video request users (VRUs) is a pressing problem. This paper uses social stability (SS) and video loading duration (VLD)-tolerant property to group VRUs and seed users (SUs) to offload BS traffic. We define the average amount of data transmission (AADT) to measure the network's capacity for offloading BS traffic. Based on this, we formulate a time-varying bipartite graph matching optimization problem. We decouple the problem into two subproblems which can be solved separately in terms of time and space. Then, we propose the socially aware D2MD user selection (SA-D2MD-S) algorithm based on finite horizon optimal stopping theory, and propose the SA-D2MD user matching (SA-D2MD-M) algorithm to solve the two subproblems. The results of simulations show that our algorithms outperform prevalent algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.7
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• pp.2286-2304
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• 2022

Blockchain is a distributed ledger that combines technologies such as cryptography, consensus mechanism, peer-to-peer transmission, and time stamping. The rapid development of blockchain has attracted attention from all walks of life, but storage scalability issues have hindered the application of blockchain. In this paper, a scalable blockchain storage model based on Distributed Hash Table (DHT) and the InterPlanetary File System (IPFS) was proposed. This paper introduces the current research status of the scalable blockchain storage model, as well as the basic principles of DHT and the InterPlanetary File System. The model construction and workflow are explained in detail. At the same time, the DHT network construction mechanism, block heat identification mechanism, new node initialization mechanism, and block data read and write mechanism in the model are described in detail. Experimental results show that this model can reduce the storage burden of nodes, and at the same time, the blockchain network can accommodate more local blocks under the same block height.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.168-182
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• 2020

Spoofing attacks, especially replay attacks, pose great security challenges to automatic speaker verification (ASV) systems. Current works on replay attacks detection primarily focused on either developing new features or improving classifier performance, ignoring the effects of feature variability, e.g., the channel variability. In this paper, we first establish a mathematical model for replay speech and introduce a method for eliminating the negative interference of the channel. Then a novel feature is proposed to detect the replay attacks. To further boost the detection performance, four post-processing methods using normalization techniques are investigated. We evaluate our proposed method on the ASVspoof 2017 dataset. The experimental results show that our approach outperforms the competing methods in terms of detection accuracy. More interestingly, we find that the proposed normalization strategy could also improve the performance of the existing algorithms.

• Journal of the Korea Computer Industry Society
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• v.5 no.1
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• pp.1-8
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• 2004

As more and more information is processed and stored in the digital form, many techniques and systems have been developed for service multimedia informations in wireless internet. In this paper, we propose MSPOB(Multimedia Statistics Post Office Box) structure for service datum which are related with similarity to subject a set of documents through grouping. The proposed structure is determined by relationship of datum based on count index and inverted file and is determined it through the semantic similarity between objects

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.7
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• pp.2919-2937
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• 2020

Post-Quantum Cryptography (PQC) is rapidly developing as a stable and reliable quantum-resistant form of cryptography, throughout the industry. Similarly to existing cryptography, however, it does not prevent a third-party from using the secret key when third party obtains the secret key by deception, unauthorized sharing, or unauthorized proxying. The most effective alternative to preventing such illegal use is the utilization of biometrics during the generation of the secret key. In this paper, we propose a biometric-based secret key generation scheme for multivariate quadratic signature schemes, such as Rainbow. This prevents the secret key from being used by an unauthorized third party through biometric recognition. It also generates a shorter secret key by applying Principal Component Analysis (PCA)-based Confidence Interval Analysis (CIA) as a feature extraction method. This scheme's optimized implementation performed well at high speeds.

• Journal of Information Management
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• v.40 no.4
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• pp.151-171
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• 2009

This study is to investigate dissatisfaction behavior of customers who purchase products on the Internet shopping mall and to find customers' dissatisfaction behavior types for effectively responding to that. Managing dissatisfaction behaviors are related to the customer satisfaction. To conduct this study, Call Center data was collected and analysed by qualitative method. The results showed that dissatisfaction of product quality and disappointment have different effects on post--purchase behaviors. Customers who feel more dissatisfaction with product quality showed the aggressive response such as exchange, refund, while customers who feel disappointment are likely to switch the shopping mall or to cancel the order. These results of customers' dissatisfaction behaviors indicate that company has to manage both product quality and the customer's experience dimension.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.19-24
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• 2018

This study investigated the academic stress and the immersion in learning in relation to AR and VR assisted instructions compared to traditional approaches. To that end, 78 $8^{th}$ graders in T and S city in Gangwondo were assigned to experimental and control groups. The experimental group received the VR and AR lessons. The academic stress was measured with the pre- and post-test scores, while the immersion in learning was measured with the post-test scores. In brief, AR and VR assisted lessons made statistically significant differences in the academic stress and immersion in learning in comparison to the traditional approaches.

• Journal of Internet Computing and Services
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• v.20 no.3
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• pp.25-31
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• 2019

Along with the recent advances in quantum computers, it is anticipated that cryptographic attacks using them will make it insecure to use existing public key algorithms such as RSA and ECC. Currently, a lot of researches are underway to replace them by devising PQC (Post Quantum Cryptography) schemes. In this paper, we propose a performance enhancement method for Lizard implementation which is one of NIST PQC standardization submission. The proposed method is able to improve the performance by 7 ~ 25% for its algorithms compared to the implementation in the submission through the techniques of various implementation aspects. This study hopes that Lizard will become more competitive as a candidate for PQC standardization.

• Journal of the Korean Data and Information Science Society
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• v.19 no.3
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• pp.775-788
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• 2008

In this study, the consumers were classified into Risk Avoidance Group, Enjoyment and Economy Group, Low Involving Group and High Involving Group by shopping propensity of the consumers and investigated the difference in their evaluation criteria and purchasing intention. The samples used in this study are 214 university students in Busan area who visited the internet shopping mall or had an experience to buy clothes through an internet. The purpose of this study is to identify how the internet university students' clothes shopping propensity and demographical factors affect the evaluation criteria and purchasing intention for clothes. And based on the results, the implications for internet clothes shopping mall are suggested and post research subject is provided as well.