• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2595-2618
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• 2018

In this paper, we investigate secure communication with the presence of multiple eavesdroppers (Eves) in a two-tier downlink dense heterogeneous network, wherein there is a macrocell base station (MBS) and multiple femtocell base stations (FBSs). Each base station (BS) has multiple users. And Eves attempt to wiretap a macrocell user (MU). To keep Eves ignorant of the confidential message, we propose a physical-layer security scheme based on cross-layer cooperation to exploit interference in the considered network. Under the constraints on the quality of service (QoS) of other legitimate users and transmit power, the secrecy rate of system can be maximized through jointly optimizing the beamforming vectors of MBS and cooperative FBSs. We explore the problem of maximizing secrecy rate in both non-colluding and colluding Eves scenarios, respectively. Firstly, in non-colluding Eves scenario, we approximate the original non-convex problem into a few semi-definite programs (SDPs) by employing the semi-definite relaxation (SDR) technique and conservative convex approximation under perfect channel state information (CSI) case. Furthermore, we extend the frame to imperfect CSI case and use the Lagrangian dual theory to cope with uncertain constraints on CSI. Secondly, in colluding Eves scenario, we transform the original problem into a two-tier optimization problem equivalently. Among them, the outer layer problem is a single variable optimization problem and can be solved by one-dimensional linear search. While the inner-layer optimization problem is transformed into a convex SDP problem with SDR technique and Charnes-Cooper transformation. In the perfect CSI case of both non-colluding and colluding Eves scenarios, we prove that the relaxation of SDR is tight and analyze the complexity of proposed algorithms. Finally, simulation results validate the effectiveness and robustness of proposed scheme.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.10
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• pp.1145-1152
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• 2014

The RFID (Radio-Frequency Identification) system is a technology to discern things by radio and an epoch-making new method to improve product management such as distribution, transport, mobilization, inventory control. However, RFID, which uses radio, is at risk for information leakage and falsification due to the vulnerability of security of the communication section. We designed the new authentication protocol by applying the tent map, which is the representative complex systems, to the RFID communication system. A more solid and simple authentication system was designed by applying the initial value sensitivity and irregularity, which are the representative characteristics of the complex system, to the reader and tag of RFID. The purpose of this paper is to verify the usability of the RFID authentication protocol design that uses the nonlinear system shown in this thesis by the new system differentiated from the authentication system that depends on the existing hash function or random numbers.

• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.412-424
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• 2016

Broadcast encryption (BE) is a cryptographic primitive that enables a sender to broadcast a message to a set of receivers in a secure channel. The efficiency of BE is measured by three factors: ciphertext transmission cost, user storage cost, and computational cost for decryption. In general, BE is applied to the environments where a large number of receivers should be accommodated, so that the transmission cost is considered as being the most important factor. In this paper, we suggest a new BE system, using Shamir's secret sharing method, which considerable reduces the transmission cost. In comparison to the previous Subset Difference (SD) system, the transmission size of our BE is longer until $r{\leq}\sqrt{n}$, but get shorter when $r{\geq}\sqrt{n}$ for number of revoked users and n number of total users. We show that the advantage can be achieved at the slight expense of both the storage and computational costs.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.37-41
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• 2012

Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.11
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• pp.1391-1400
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• 1999

이동 통신은 대기를 전달매체로 하고 이동단말기를 사용하기 때문에 가로채기나 불법사용과 같은 공격에 취약하다. 이를 극복하기 위해, 이동 통신 환경에서 이동단말기와 기지국 사이에 안전한 통신을 제공하기 위한 많은 프로토콜들이 제안되어왔다. 그러나 이동단말기의 부족한 계산능력과 전력량 때문에 공개키를 이용한 프로토콜들은 많은 장점에도 불구하고 충분히 활용되지 못했다. 본 논문에서는 이동 통신 환경에서 기지국과 이동단말기 사이의 상호인증 및 세션키 공유 프로토콜들의 성능을 향상시킬 수 있는 기법을 제안한다. 본 논문에서 제안하는 기법은 이동단말기의 비밀 정보를 기지국에게 드러나게 하지 않으면서 많은 계산을 기지국으로 하여금 대신 수행하도록 하는 것이다. 제안된 기법은 기존의 프로토콜들을 최대 5배까지 성능을 향상시키며 해당하는 만큼 이동단말기의 전력량 소모를 감소시킬 수있다.Abstract Mobile communication is more vulnerable to security attacks such as interception and unauthorized access than fixed network communication. To overcome these problems, many protocols have been proposed to provide a secure channel between a mobile station and a base station. However, these public-key based protocols have not been fully utilized due to the poor computing power and small battery capacity of mobile stations. In this paper, we propose techniques for accelerating public-key based key establishment protocols between a mobile station and a base station. The proposed techniques enable a mobile station to borrow computing power from a base station without revealing its secret information. The proposed schemes accelerate the previous protocols up to five times and reduce the amount of power consumption of mobile stations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.594-600
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• 2014

In modern warfare, securing communication channel by combatting opponents' electromagnetic attack is a crucial factor to win the war. Military satellite digital transponder is a communication payload of the next generation military satellite that maintains warfare networks operational in the presence of interfering signals by securely relaying signals between ground terminals. The transponder in this paper is classified as a partial processing transponder which performs cost effective secure relaying in satellite communication links. The control functions of transmission security achieve immunity to hostile interferences which may cause malicious effects on the link. In this paper, we present an efficient architecture for implementing the control mechanism. Two major ideas of pipelined processing in per-group control and software processing of blocked band information dramatically reduce the complexity of the hardware. A control code sequence showing its randomness with uniform distribution is exemplified and qualification test results are briefly presented.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.20-29
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• 2007

Although E-mail system is considered as a most important communication media, 'Spam' is flooding the Internet with many copies of the same message, in an attempt to force the message on people who would not otherwise choose to receive it. Most spam is commercial advertising, often for dubious products, get-rich-quick schemes, or quasi-legal services. Therefore advanced anti-spam techniques are required to basically reduce its transmission volume on sender mail server or MTA, etc. In this study, we propose a new sender authentication model with encryption function based on modified DomainKey with SMS for Spam mail protection. From the SMS message, we can get secret information used for verification of its real sender on e-mail message. And by distributing this secret information with SMS like out-of-band channel, we can also combine proposed modules with existing PGP scheme for secure e-mail generation and authentication steps. Proposed scheme provide enhanced authentication function and security on Spam mail protection function because it is a 'dual mode' authentication mechanism.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.178-182
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• 2000

During the past five years, there has born tremendous interest worldwide in the possibility of exploiting chaos in wideband communication systems. Many different demodulation techniques have been proposed up to date. They can be divided into two basic categories. In the first approach, like the conventional coherent demodulation techniques, the chaotic signal has to be recovered from the received noisy signal by synchronization. However, the chaotic synchronization techniques published to data are so sensitive to the channel noise and distortion that these techniques can not be used in radio communications. In the second approach, the demodulation is carried out nonsynchronization. This paper surveys the different chaotic communication techniques that can be implemented nonsynchronization and compares the threshold and BER of the different methods. Finally, FM-DCSK is introduced the first step for apply to wideband chaos digital CDMA, where the data is not limited by the inherent nonperiodic property of the chaotic signal.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.123-129
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• 2018

Recently, as required wireless communication traffic increase, millimeter wave mobile technologies that can secure broadband spectrum are gaining attention. However, the path loss is high in the millimeter wave channel. Massive MIMO system is being researched in which can complement the path loss by beamforming by equiped large-scale antenna at the base station. While legacy beamforming techniques have analog and digital methods, practical difficulties exist for application to massive MIMO systems in terms of system complexity and cost. Therefore, this paper studies a hybrid beamforming scheme for massive MIMO system in the millimeter wave band. Also this paper considers spatial multiplexing scheme to serve multi-users with multiple received antennas. Gains of the beamforming and the spatial multiplexing schemes are evaluated by analyzing the spectral efficiency.

• Journal of Arbitration Studies
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• v.29 no.4
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• pp.33-55
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• 2019

This study is aimed at drawing up improvement measures in connection with the resolution of claims, one of the major constraints in revitalizing South-North Korean economic cooperation. To that end, we first looked at the structure of South-North Korean economic cooperation and the institutional status related to resolving the claims. Also we analyzed the current status of the claims in the process of promoting South-North Korean economic cooperation by companies and the provisions of the claims between the parties in order to derive any problems. Through these research results, we were able to identify directions and implications for efficient improvement of the causes of several South-North Korean economic cooperation claims. First, at the corporate level, there is a need to create specific details of a contract for resolving disputes and to add additional third-party coordination functions in the relevant clause of the contract in preparation for the occurrence of a dispute. In addition, it is necessary to seek ways to advance jointly with corporations in China and other third countries in order to secure stability. Second, the government should continue to discuss ways of promoting South-North Korean commercial arbitration with North Korea so that follow-up measures can be completed as soon as possible. In addition, a two-track strategy is suggested to provide a practical negotiation channel at the private level. Also it is necessary to be active in persuading North Korea to join the international arbitration treaty in preparation for the activation of full-fledged economic exchanges.