• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.59-69
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• 2004

Password-based authenticated group key exchange protocols provide a group of user, communicating over a public(insecure) channel and holding a common human-memorable password, with a session key to be used to construct secure multicast sessions for data integrity and confidentiality. In this paper, we present a password-based authenticated group key exchange protocol and prove the security in the random oracle model and the ideal cipher model under the intractability of the decisional Diffie-Hellman(DH) problem and computational DH problem. The protocol is scalable, i.e. constant round and with O(1) exponentiations per user, and provides forward secrecy.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.5
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• pp.165-176
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• 2004

Al-Riyami and Paterson$^{[1]}$ suggested the new public key paradigm which is called the certificateless public key system. This system takes the advantages of both traditional PKC and ID-based PKC. It does not require the use of certificates of the public key and does not have the key escrow problem caused from the ID-based cryptosystem. In this paper, we propose an efficient certificateless public key encryption scheme which satisfies mutual authentication. The security of our protocol is based on the hardness of two problems; the computational Diffie-Hellman problem(CDHP) and the bilinear Diffie-Hellman problem(BDHP). We also give a formal security model for both confidentiality and unforgeability, and then show that our scheme is probably secure in the random oracle model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.3
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• pp.35-42
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• 2007

We describe the problem of reducing the key material in the Even-Mansour cipher without security degradation. Even and Mansour proposed a block cipher based on XORing secret key material just prior to and after applying random oracle permutation P such that $C=k_2\bigoplus P(M\bigoplus k_1)$. Recently, Gentry and Ramzan showed that this scheme in the random permutation oracle can be replaced by the four-round Feistel network construction in the random function oracle and also proved that their scheme is super-pseudorandom. In this paper we reduce the key size from 2n to n, which is the optimal key size of Even-Mansour cipher in the random function oracle model and also give almost the same level of security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.5
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• pp.73-92
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• 2005

Joux's tripartite key agreement protocol is one of the most prominent developments in the area of key agreement. Although certificate-based and ID-based authentication schemes have been proposed to provide authentication for Joux's protocol, no provably secure password-based one round tripartite key agreement protocol has been proposed yet. We propose a secure one round password-based tripartite key agreement protocol that builds on Joux's protocol and adapts PAK-EC scheme for password-based authentication, and present a proof of its security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.6
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• pp.1301-1313
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• 2012

The importance of protecting personal information is increasing day by day due to invasion of privacy, and data encryption is the most effective way to eliminate it. However, current data encryption methods tend to having problems for applying in practical fields because of critical issues such as low performances and frequent changes of applications. In order to find proper solutions for data security, this paper reviews data encryption technologies and experiments on performance of encrypted data in Oracle Database. On top of that, this paper analyses a data encryption technique not only efficiency of performance but also minimization of application changes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.201-208
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• 2010

The classical iterated hash function is vulnerable to a multi-collision attack. Gauravaram et al. proposed 3C and 3C+ hash functions, in which an accumulation chain is added to usual Merkle-Damgard changing. Their goal is to design composition schemes resistant to generic attacks of Joux's type, but Joscak and Tuma have shown that 3C and 3C+ schemes are not better than Merkle-Damgard scheme in term of security against multi-collision attacks under some mild assumptions. In this dissertation, in order to increase security of 3C hash function, we proposed secure double pipe hash function which was effectively using XOR and XNOR operations per blocks of message. We seek to improve on the work of Lucks in a way. Proposed secure double pipe hash function takes resistance to multi-block collision, fixed point and pre-image attacks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.3
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• pp.563-577
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• 2018

In order to support secure communication in VANET(Vehicular Ad hoc Network), messages exchanged between vehicles or between vehicle and infrastructure must be authenticated. In this paper, we propose a hierarchical anonymous authentication system for VANET. The proposed system model reduces the overhead of PKG, which is a problem of previous system, by generating private keys hierarchically, thereby enhancing practicality. We also propose a two-level hierarchical identity-based signature(TLHIBS) scheme without pairings so that improve efficiency. The proposed scheme protects the privacy of the vehicle by satisfying conditional privacy and supports batch verification so that efficiently verifies multiple signatures. Finally, The security of the proposed scheme is proved in the random oracle model by reducing the discrete logarithm problem(DLP) whereas the security proof of the previous ID-based signatures for VANET was incomplete.

• Journal of the Korean Society for information Management
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• v.16 no.4
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• pp.109-123
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• 1999

We are faced with a paradox in the age of information as finding quality information on the Internet becomes a more challenging task because of information overload. This paper describes the prototype for “IPL-Korea” (Internet Public Library in Korea) project which is an attempt to provide the public with quality information in the form of a metadata system. The system involves cataloging of resources, i.e. websites, that are filtered by library and information science majors as well as information professionals. The user focus of this system is on children, youth, women, and seniors; various classification schemes and resource descriptions relevant for each user group are incorporated into the system to allow efficient browsing of the resources. A thesaurus for “IPL-Korea”, which is based on the ERIC thesaurus, is being constructed for easy manipulation of the breath of searching. The “IPL-Korea” metadata system employs the entity-relationship model in the design of its conceptual schema. Metadata is being stored in the Oracle database system and Web interfaces to this database are provided through ASP, ColdFusion, and JAVA technology.

• Convergence Security Journal
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• v.6 no.3
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• pp.21-28
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• 2006

Beginning flag security it was limited in Firewall but currently many information security solutions like Anti-virus, IDS, Firewall are come to be many. For efficiently managing different kinds of information security products ESM (Enterprise Security management) are developed and operated. Recently over the integrated security management system, TMS (Threat Management System) is rising in new area of interest. It follows in change of like this information security product and also collection information is being turning out diversification. For managing cyber threats, we have to analysis qualitative information (like vulnerabilities and malware codes, security news) as well as the quantity event logs which are from information security products of past. Information Threats and Vulnerability Auto Collector raises the accuracy of cyber threat judgement and can be utilized to respond the cyber threat which does not occur still by gathering qualitative information as well as quantity information.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.1
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• pp.20-34
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• 2009

We newly propose a multiple and unlinkable identity-based public key encryption scheme which allows the use of a various number of identity-based public keys in different groups or applications while keeping a single decryption key so that the decryption key can decrypt every ciphertexts encrypted with those public keys. Also our scheme removes the use of certificates as well as the key escrow problem so it is functional and practical. Since our public keys are unlinkable, the user's privacy can be protected from attackers who collect and trace the user information and behavior using the known public keys. Furthermore, we suggest a decryption key renewal protocol to strengthen the security of the single decryption key. Finally, we prove the security of our scheme against the adaptive chosen-ciphertext attack under the random oracle model.