• Journal of Korea Multimedia Society
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• v.20 no.3
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• pp.500-510
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• 2017

Recently Lee et al. proposed an improved symmetric key-based remote user authentication scheme to eliminate the security weaknesses of Kumari et al.'s scheme. They hence claimed that their scheme is secure to various well-known attacks. However, we found that Lee et al.'s scheme is still insecure against outsider attack, smart card stolen and off-line password guessing attack. To overcome these security vulnerabilities, we propose an enhanced authentication scheme with key-agreement which is based on the fuzzy-extractor. Furthermore, we prove that the proposed scheme is more secure, and that it serves to gratify all of the required security properties. Finally, we compare the performance and functionality of the proposed scheme with those of previous schemes.

• Convergence Security Journal
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• v.12 no.4
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• pp.85-90
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• 2012

DES is a 64-bit binary, and each block is divided into units of time are encrypted through an encryption algorithm. The same key as the symmetric algorithm for encryption and decryption algorithms are used. Conversely, when decryption keys, and some differences may apply. The key length of 64 bits are represented by two ten thousand an d two 56-bit is actually being used as the key remaining 8 bits are used as parity check bits. The 64-bit block and 56-bit encryption key that is based on a total of 16 times 16 modifier and spread through the chaos is completed. DES algorithm was chosen on the strength of the password is questionable because the most widely available commercially, but has been used. In addition to the basic DES algorithm adopted in the future in the field by a considerable period are expected to continue to take advantage of the DES algorithm effectively measures are expected to be in the field note.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2563-2568
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• 2009

Although a symmetric cryptographic system has many advantages in speed of encryption decryption, the security problems with the distribution method of secret keys have been still raised. Especially, the distribution method of secret keys for unspecified individuals who want secret communication is becoming a core issue. As a simple solution to this issue, Diffie-Hellman key exchange methods were proposed, but proved to be insufficient in depending MITM(Main In The Middle) attacks. To find effective solution to problems mentioned above, this paper proposes the strengthened Diffie-Hellman key exchange methods applied for the mobile-phone channel which are widely used. This paper emphasizes the way to distribute the synthesized session keys to the sender and the receiver, which are created with authentication numbers exchanged between the mobile-phones and Diffie-Hellman key. Using proposed ways, MITMattacks can be effectively defended.

• Journal of Korea Multimedia Society
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• v.20 no.4
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• pp.614-628
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• 2017

Recently, Due to the rapid development of the internet and IT technology, users can conveniently use various services provided by the server anytime and anywhere. However, these technologies are exposed to various security threat such as tampering, eavesdropping, and exposing of user's identity and location information. In 2016, Nikooghadam et al. proposed a lightweight authentication and key agreement protocol preserving user anonymity. This paper overcomes the vulnerability of Nikooghadam's authentication protocol proposed recently. This paper suggests an enhanced remote user authentication protocol that protects user's password and provides perfect forward secrecy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1249-1272
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• 2016

In this paper, we propose a symmetric key establishment scheme for wireless sensor networks which tries to minimize the resource usage while satisfying the security requirements. This is accomplished by taking advantage of the communication pattern of wireless sensor networks and adopting heterogeneous wireless sensor networks. By considering the unique communication pattern of wireless sensor networks due to the nature of information gathering from the physical world, the number of keys to be established is minimized and, consequently, the overhead spent for establishing keys decreases. With heterogeneous wireless sensor networks, we can build a hybrid scheme where a small number of powerful nodes do more works than a large number of resource-constrained nodes to provide enhanced security service such as broadcast authentication and reduce the burden of resource-limited nodes. In addition, an on-demand key establishment scheme is introduced to support extra communications and optimize the resource usage. Our performance analysis shows that the proposed scheme is very efficient and highly scalable in terms of storage, communication and computation overhead. Furthermore, our proposed scheme not only satisfies the security requirements but also provides resilience to several attacks.

• Computers and Concrete
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• v.22 no.2
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• pp.209-220
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• 2018

In order to evaluate the effect of hybrid fibers on the flexural performance of tunnel segment at room temperature, twelve reinforced self-consolidating concrete (SCC) symmetric inclination beams containing steel fiber, macro polypropylene fiber, micro polypropylene fiber, and their hybridizations were studied under combined loading of flexure and axial compression. The results indicate that the addition of mono steel fiber and hybrid fibers can enhance the ultimate bearing capacity and cracking behavior of tested beams. These improvements can be further enhanced along with increasing the content of steel fiber and macro PP fiber, but reduced with the increase of the reinforcement ratio of beams. The hybrid effect of steel fiber and macro PP fiber was the most obvious. However, the addition of micro PP fibers led to a degradation to the flexural performance of reinforced beams at room temperature. Meanwhile, the hybrid use of steel fiber and micro polypropylene fiber didn't present an obvious improvement to SCC beams. Compared to micro polypropylene fiber, the macro polypropylene fiber plays a more prominent role on affecting the structural behavior of SCC beams. A calculation method for ultimate bearing capacity of flexural SCC symmetric inclination beams at room temperature by taking appropriate effect of hybrid fibers into consideration was proposed. The prediction results using the proposed model are compared with the experimental data in this study and other literature. The results indicate that the proposed model can estimate the ultimate bearing capacity of SCC symmetric inclination beams containing hybrid fibers subjected to combined action of flexure and axial compression at room temperature.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.151-153
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• 2005

무선 센서 네트워크는 방대한 응용분야와 유비쿼터스 환경 하에서 중요한 한 부분을 차지하며 그 유용성을 입증하고 있다. 이런 무선 센서 네트워크의 센서 노드는 작은 크기를 바탕으로 목표 장소에 임의로 배치되어 다양한 데이터를 수집하는 능력이 탁월하다 하지만 이런 장점은 센서 노드의 한정된 하드웨어 능력과 전원공급 문제, 물리적 노출 문제로 인해 스스로를 위험에 노출시키는 여지를 만들게 되었다. 즉 일반적으로 사용되어지는 네트워크 보안 방법을 무선 센서 네트워크에 적응하기에는 센서 노드 능력에 한계가 있으며, 환경적 요소로 인해 불가능하다. 따라서 무선 센서 네트워크의 특성을 감안한 효과적인 보안 방법이 필요하며, 이런 맥락에 본 논문은 무선 센서 네트워크의 하드웨어적인 한계를 감안한 대칭키(Symmetric key) 기반의 키 분배 기법을 제안하고자 한다. 제안하는 기법에서는 모든 노드가 공통으로 소유한 전체 마스터 키(master key)와 의사 난수 생성기(pseudo random number generator:PRNG), 그리고 특정 대상으로부터 분배되는 난수(random number)의 조합을 통해 임의의 키를 생성, 갱신함으로써 다양한 종류의 무선 센서 네트워크 모델에 유연하게 대처할 수 있도록 하였다. 또한 이를 위한 통신 회수를 최소화함으로써 효율성을 제공해 준다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.920-923
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• 2011

VANET에서 V2V, V2I 통신을 통해 다양한 서비스를 이용하기 위해서는 안전하고 신뢰성 있는 통신이 보장되어야 한다. 이를 위해 다양한 연구들이 진행되었으며, 기존 연구들 중 대칭키를 사용한 방법으로는 RAISE가 있다. RAISE는 대칭키를 기반으로 하였기 때문에 다른 연구들 보다 낮은 통신 및 연산 비용을 가진다. 하지만 메시지에 대한 인증을 즉시 제공하지 못하며, RSU가 불능이 되거나 존재하지 않는 환경에서는 차량이 서비스를 제공받지 못한다는 문제점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 대칭키 기반의 그룹키와 식별자를 사용하여 메시지 인증을 제공하고, 메시지 인증과정에서 RSU에 비의존적인 인증 프로토콜을 제안한다.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.1-16
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• 2005

This paper propose not only MDIT(Mobile Digital Investment Trust) agent design for Trust Investment under Mobile E-commerce environment, but also the symmetric key algorithm 3BC(Bit, Byte and Block Cypher) and the public encryption algorithm F2mECC for solving the problems of memory capacity, CPU processing time, and security that mobile environment has. In Particular, the MDIT Security Agent is the banking security project that introduces the concept of investment trust in mobile e-commerce, This mobile security protocol creates a shared secrete key using F2mECC and then it's value is used for 3BC that is block encryption technique. The security and the processing speed of MDIT agent are enhanced using 3BC and F2mECC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.653-663
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• 2002

The signature-then-encryption based on RSA scheme provides forward secrecy, but requires 4 modulo exponentiation operations in total, and the signcryption scheme proposed by Zheng simultaneously fulfills both the functions of digital signature and symmetric key encryption in a logically single step, and with a computational cost significantly smaller than that required by the current standard signature-then-encryption, but it can not provide forward secrecy. In this paper, we propose an enhanced signcryption scheme which can provide forward secrecy with lower computational cost and lower communication overhead comparing with those of the signature-then-encryption based on RSA, and with a similar communication overhead of Zheng's scheme. The proposed scheme can be also easily modified to the direct signature verification scheme by the recipient without using the recipient's private key. Additionally, we suggest a new design protocol with server-supported signatures which solves the CRLs(Certificate Revocation Lists) burden and provides non-repudiation of origin. This protocol with server-supported signatures also can be applied to the original signcryption scheme proposed by Zheng in order to improve security.