• 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.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.33-38
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• 2005

In this paper, we propose a password-based authenticated key exchange protocol which authenticates each other and shares a session key using only a small memorable password between a client and a server over an insecure channel. The proposed protocol allows an authenticated client to freely change a his/her own password. The protocol is also secure against various attacks and provides the perfect forward secrecy. Furthermore, it has good efficiency compared with the previously well-known password-based protocols with the same security requirements.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.3
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• pp.67-78
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• 2010

CAS(Conditional Access System) is used in Pay-TV System to prohibit unauthorized user(s) accessing the contents in IPTV broadcasting environment. In the CAS, Smartcard transfers CW which is necessary in the process of descrambling the scrambled program to STB. CW hacking problem is one of the most serious problems in pay-TV system. There have been many researches on generating secure communication channel between smartcard and STB for secure transmitting, But they had problems in efficiency and security. In this paper, we propose a lightweight key agreement protocol based on a symmetric key algorithm. We show that our proposed protocol is more efficient than existing protocols by comparing the amount of computations, and analyzing the security requirement of the proposed protocol.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.298-305
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• 2014

In this study, a novel Randomly Shifted Certification Authority Authentication protocol was used in ad hoc networks to provide authentication by considering the MAC layer characteristics. The nodes achieve authentication through the use of public key certificates issued by a CA, which assures the certificate's ownership. As a part of providing key management, the active CA node transfers the image of the stored public keys to other idle CA nodes. Finally the current active CA randomly selects the ID of the available idle CA and shifts the CA ownership by transferring it. Revoking is done if any counterfeit or duplicate non CA node ID is found. Authentication and integrity is provided by preventing MAC control packets, and Enhanced Hash Message Authentication Code (EHMAC) can be used. Here EHMAC with various outputs is introduced in all control packets. When a node transmits a packet to a node with EHMAC, verification is conducted and the node replies with the transmitter address and EHMAC in the acknowledgement.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.439-441
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• 2002

Real-time Transport Protocol (RTP) is widely used in VoIP stacks charging the multimedia data delivery. Concerning with payload protection of RTP packets, Secure RTP has been discussed in IETF AVT group to provide confidentiality and authentication features using block ciphering and message authentication coding. However, Secure RTP only concentrates on payload protection. Signcryption is a good candidate for key agreement. This paper proposes a key establishment protocol using Signcryption and shows example implementation of a secure VoIP application based on Secure RTP with the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.6188-6204
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• 2017

Over the years, more password-based authentication key agreement schemes using chaotic maps were susceptible to attack by off-line password guess attack. This work approaches this problem by a new method--new theorem of chaotic maps: $T_{a+b}(X)+T_{a-b}(X)=2T_a(X)T_b(X)$,(a>b). In fact, this method can be used to design two-party, three-party, even in N-party intelligently. For the sake of brevity and readability, only a two-party instance: a novel Two-party Password-Authenticated Key Agreement Protocol is proposed for resisting password guess attack in this work. Compared with the related literatures recently, our proposed scheme can be not only own high efficiency and unique functionality, but is also robust to various attacks and achieves perfect forward secrecy. For capturing improved ratio of security and efficiency intuitively, the paper firstly proposes a new parameter called security/efficiency ratio(S/E Ratio). The higher the value of the S/E Ratio, the better it is. Finally, we give the security proof and the efficiency analysis of our proposed scheme.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.217-222
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• 2012

Group communication on the Internet is exploding in popularity. Video conferencing, Enterprise IM, desktop sharing, and numerous forms of e-commerce are but a few examples of the ways in which the Internet is being used for business. The growing use of group communication has highlighted the need for advances in security. There are several approaches to securing user identities and other information transmitted over the Internet. One of the foundations of secure communication is key management, a building block for encryption, authentication, access control, and authorization.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.1
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• pp.51-61
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• 2010

Koinonia system is designed to fully utilize the advantage of Binary CDMA so as to guarantee QoS in wireless networks. In this paper, we propose the new network structure based on this system and refer to it as BLAN(Binary CDMA LAN). Although BLAN is similar structure to IEEE 802.11 WLAN, it will ensure the fast handover and QoS. We also propose the AKA(Authentication and Key Agreement) protocol and Reauthentication protocol to be used for communication in BLAN. These protocols are securely and efficiently designed using the user identity module to support the more powerful authentication. Hence, BLAN, including the proposed protocols, will support the high mobility and security. In conclusion, we expect that BLAN can be applied to future infrastructure on special environment, and it can be helpful showing the new network model which alternate WLAN.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.60-71
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• 2006

Group key agreement protocols are designed to allow a group of parties communicating over a public network to securely and efficiently establish a common secret key, Over the years, a number of solutions to the group key agreement protocol have been proposed with varying degrees of complexity, and the research relating to group key agreement to securely communicate among a group of members in integrated wired and wireless networks has been recently proceeded. Both features of wired computing machines with the high-performance and those of wireless devices with the low-power are considered to design a group key agreement protocol suited for integrated wired and wireless networks. Especially, it is important to reduce computational costs of mobile devices which have the limited system resources. In this paper, we present an efficient group key agreement scheme which minimizes the computational costs of mobile devices and is well suited for this network environment and prove its security.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.157-168
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• 2005

Group key agreement protocols are designed to provide a group of parties securely communicating over a public network with a session key. The mobile computing architecture is asymmetric in the sense of computational capabilities of participants. That is, the protocol participants consist of the stationary server(application servers) with sufficient computational Power and a cluster of mobile devices(clients) with limited computational resources. It is desirable to minimize the amount of computation performed by each group member in a group involving low-power mobile devices such as smart cards or personal digital assistants(PDAs). Furthermore we are required to update the group key with low computational costs when the members need to be excluded from the group or multiple new members need to be brought into an existing group. In this paper, we propose a dynamic group key protocol which offers computational efficiency to the clients with low-power mobile devices. We compare the total communicative and computational costs of our protocol with others and prove its suity against a passive adversary in the random oracle model.