• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.814-821
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• 2007

A hybrid method is presented for efficient computation of turbulent flow noise at low Mach numbers. In this method, the turbulent flow field is computed by incompressible large eddy simulation (LES), while the acoustic field is computed with the linearized perturbed compressible equations (LPCE) derived in this study. Since LPCE is computed on the rather coarse acoustic grid with the flow variables and source term obtained by the incompressible LES, the computational efficiency of calculation is greatly enhanced. Furthermore, LPCE suppress the instability of perturbed vortical mode and therefore secure consistent and stable acoustic solutions. The proposed LES/LPCE hybrid method is applied to three low Mach number turbulent flow noise problems: i) circular cylinder, ii) isolated flat plate, and iii) interaction between cylinder wake and airfoil. The computed results are closely compared with the experimental measurements.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.881-896
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• 2016

Certificate-based cryptography is a useful public key cryptographic primitive that combines the merits of traditional public key cryptography and identity-based cryptography. It not only solves the key escrow problem inherent in identity-based cryptography, but also simplifies the cumbersome certificate management problem in traditional public key cryptography. In this paper, by giving a concrete attack, we first show that the certificate-based encryption scheme without bilinear pairings proposed by Yao et al. does not achieve either the chosen-ciphertext security or the weaker chosen-plaintext security. To overcome the security weakness in Yao et al.'s scheme, we propose an enhanced certificate-based encryption scheme that does not use the bilinear pairings. In the random oracle model, we formally prove it to be chosen-ciphertext secure under the computational Diffie-Hellman assumption. The experimental results show that the proposed scheme enjoys obvious advantage in the computation efficiency compared with the previous certificate-based encryption schemes. Without costly pairing operations, it is suitable to be employed on the computation-limited or power-constrained devices.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3339-3352
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• 2016

In ciphertext-policy attribute-based encryption (CP-ABE) scheme, a user's secret key is associated with a set of attributes, and the ciphertext is associated with an access policy. The user can decrypt the ciphertext if and only if the attribute set of his secret key satisfies the access policy specified in the ciphertext. In the present schemes, access policy is sent to the decryptor along with the ciphertext, which means that the privacy of the encryptor is revealed. In order to solve such problem, we propose a CP-ABE scheme with hidden access policy, which is able to preserve the privacy of the encryptor and decryptor. And what's more in the present schemes, the users need to do excessive calculation for decryption to check whether their attributes match the access policy specified in the ciphertext or not, which makes the users do useless computation if the attributes don't match the hidden access policy. In order to solve efficiency issue, our scheme adds a testing phase to avoid the unnecessary operation above before decryption. The computation cost for the testing phase is much less than the decryption computation so that the efficiency in our scheme is improved. Meanwhile, our new scheme is proved to be selectively secure against chosen-plaintext attack under DDH assumption.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.3
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• pp.27-36
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• 2015

This research studies the adequate size standard of Seogwipo cruise terminal CIQ facility that is scheduled to be built around Gangjeong harbor area in Seogwipo-city. In order to respond to the highly increasing number of passenger cruise ships compared to Seogwipo cruise terminal design in 2010, the adequate size standard of Seogwipo cruise terminal CIQ facility was examined for passenger service level grade. Based on size computation elements such as the number of passengers of cruise ships with the largest size of port entry, ship landing rate, passenger processing ratio, and surge factor, the CIQ facility size for each service level grade was reviewed. As a result, the area of 2,971m2 (A grade), 2,409 m2 (B grade), and 2,088 m2 (C grade) were computed. This showed that the area of B grade was about 82% and C grade 70% compared to the area of A grade. The CIQ facility size computed for each service level grade in this research was analyzed that its area needed to be increased by 322% at least and 458% at most, compared to the CIQ facility area of 649m2 of the existing design (2010). In order to respond to the increasing number of cruise passengers, provide high-level passenger service, and improve the international image of Jeju, Seogwipo cruise terminal should secure the size that is equal to or higher than the B grade of service level.

• Convergence Security Journal
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• v.6 no.1
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• pp.83-90
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• 2006

Recently, the security for RFID/USN environment is divided into network security and RFID security. The authentication protocol design for RFID security is studied to protect user privacy in RFID system. However, the study of efficient authentication protocol for RFID system is not satisfy a security for low-cost RFID tag and user privacy. Therefore, this paper proposes a secure matrix-based RFID authentication protocol that decrease communication overhead and computation. In result, the Matrix-based RFID authentication protocol is an effective authentication protocol compare with HB and $HB^+$ in traffic analysis attack and trace location attack.

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.3
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• pp.168-174
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• 2010

User authentication is an important requirement to provide secure network service. Therefore, many authentication schemes have been proposed to provide secure authentication, such as key agreement and anonymity. However, authority of scheme is limited to one's self. It is inefficient when authenticated users grant a certification to other users who are in an organization which has a hierarchical structure, such as a company or school. In this paper, we propose the first authentication scheme to use Attributes-Based Re-encryption that creates a certification to other users with specified attributes. The scheme, which has expanded from Rhee et al. scheme, has optimized computation performance on a smart card, ensuring the user's anonymity and key agreement between users and server.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.6
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• pp.2534-2553
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• 2020

Recently, numerous certificateless encryption (CLE) schemes have been introduced. The security proofs of most schemes are given under the random oracle model (ROM). In the standard model, the adversary is able to calculate the hash function instead of asking the challenger. Currently, there is only one scheme that was proved to be secure in SM. In this paper, we constructed a new CLE scheme and gave the security proofs in SM. In the new scheme, the size of the storage space required by the system is constant. The computation cost is lower than other CLE schemes due to it needs only two pairing operations.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.993-996
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• 1999

A mobile agent is a program which is capable of migrating autonomously from host to host in the heterogeneous network, to perform some computation on behalf of the user. Mobile agents have many advantages in the distributed computing environment. But they are likely to suffer many attacks on the security due to the mobility. In order to make use of a mobile agent in the real applications, the security issues must be addressed. We deal with the problem which is concerned with protecting a mobile agent in transit and detecting a mobile agent clone. In this paper we propose a trust center based secure mobile agent transfer protocol. This protocol transfers a mobile agent securely from host to host and detects a mobile agent clone. We further show the security of the protocol against many attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.5135-5149
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• 2015

Communications among multi-party must be fast, cost effective and secure. Today's computing environments such as internet conference, multi-user games and many more applications involve multi-party. All participants together establish a common session key to enable multi-party and secure exchange of messages. Multi-party password-based authenticated key exchange scheme allows users to communicate securely over an insecure network by using easy-to-remember password. Kwon et al. proposed a practical three-party password-based authenticated key exchange (3-PAKE) scheme to allow two users to establish a session key through a server without pre-sharing a password between users. However, Kwon et al.'s scheme cannot meet the security requirements of key authentication, key confirmation and anonymity. In this paper, we present a novel, simple and efficient multi-party password-based authenticated key exchange (M-PAKE) scheme based on the elliptic curve cryptography for mobile environment. Our proposed scheme only requires two round-messages. Furthermore, the proposed scheme not only satisfies security requirements for PAKE scheme but also achieves efficient computation and communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2554-2571
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• 2014

Certificate-based cryptography is a new cryptographic paradigm that provides an interesting balance between identity-based cryptography and traditional public key cryptography. It not only simplifies the complicated certificate management problem in traditional public key cryptography, but also eliminates the key escrow problem in identity-based cryptography. As an extension of the signcryption in certificate-based cryptography, certificate-based signcryption provides the functionalities of certificate-based encryption and certificate-based signature simultaneously. However, to the best of our knowledge, all constructions of certificate-based signcryption in the literature so far have to be based on the costly bilinear pairings. In this paper, we propose a certificate-based signcryption scheme that does not depend on the bilinear pairings. The proposed scheme is provably secure in the random oracle model. Due to avoiding the computationally-heavy paring operations, the proposed scheme significantly reduces the cost of computation and outperforms the previous certificate-based signcryption schemes.