• The Journal of the Korea Contents Association
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• v.17 no.7
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• pp.571-578
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• 2017

In order to approach information system through smart device and pc, user has to authenticate him or herself via user authentication. At that time when user tries reaching the system, well-used user authentication technologies are ID/PW base, OTP, certificate, security card, fingerprint, etc. The ID/PWbased method is familiar to users, however, it is vulnerable to brute force cracking, keylogging, dictionary attack. so as to protect these attacks, user has to change the passwords periodically as per password combination instructions. In this paper, we designed and implemented a user authentication system using smartphone's USIM without using password while enhancing security than existing ID / PW based authentication technology.

• 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.7 no.2
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• pp.27-42
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• 1997

We propose a new authentication and key distribution protocol which is efficient and reliable for password-based systems. Various guessing attacks have been detected in applying conventional protocols to the password-based systems and additional overheads have been made in refined protocols to defeat those attacks. Using a one-time pad and a strong hash function, our proposed protocol promotes reliability and efficiency. Compared with other protocols, our protocol is secure against various protocol attacks including guessing attacks. In addition, this protocol is efficient in reducing communication and computation costs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.4
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• pp.207-215
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• 2014

Password based authentication systems are most widely used for user convenience in web services. However such authentication systems are known to be vulnerable to various attacks such as password guessing attack, dictionary attack and key logging attack. Besides, many of the web systems just provide user authentication in a one-way fashion such that web clients cannot verify the authenticity of the web server to which they set access and give passwords. Therefore, it is too difficult to protect against DNS spoofing, phishing and pharming attacks. To cope with the security threats, web system adopts several enhanced schemes utilizing one time password (OTP) or long and strong passwords including special characters. However there are still practical issues. Users are required to buy OTP devices and strong passwords are less convenient to use. Above all, one-way authentication schemes generate several vulnerabilities. To solve the problems, we propose a multi-channel, multi-factor authentication scheme by utilizing QR-Code. The proposed scheme supports both user and server authentications mutually, thereby protecting against attacks such as phishing and pharming attacks. Also, the proposed scheme makes use of a portable smart device as a OTP generator so that the system is convenient and secure against traditional password attacks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.63-70
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• 2015

The numerous improved schemes of user authentication based on password have been proposed in order to prevent the data access from the unauthorized person. The importance of user authentication has been remarkably growing in the expanding application areas of wireless sensor networks. Recently, emerging wireless sensor networks possesses a hierarchy among the nodes which are divided into cluster heads and sensor nodes. Such hierarchical wireless sensor networks have more operational advantages by reducing the energy consumption and traffic load. In 2012, Das et al. proposed a user authentication scheme to be applicable for the hierarchical wireless sensor networks. Das et al. claimed that their scheme is effectively secure against the various security flaws. In this paper, author will prove that Das et al.'s scheme is still vulnerable to man-in-the-middle attack, password guessing/change attack and does not support mutual authentication between the user and the cluster heads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1597-1605
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• 2015

Password authenticated key exchange (PAKE) is a protocol that a client stores its password to a server, authenticates itself using its password and shares a session key with the server. In multi-server PAKE, a client splits its password and stores them to several servers separately. Unless all the servers are compromised, client's password will not be disclosed in the multi-server setting. In attribute-based encryption (ABE), a sender encrypts a message M using a set of attributes and then a receiver decrypts it using the same set of attributes. In this paper, we introduce multi-server PAKE protocol that utilizes a set of attributes of ABE as a client's password. In the protocol, the client and servers do not need to create additional public/private key pairs because the password is used as a set of public keys. Also, the client and the servers exchange only one round-trip message per server. The protocol is secure against dictionary attacks. We prove our system is secure in a proposed threat model. Finally we show feasibility through evaluating the execution time of the protocol.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.130-137
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• 2003

This paper proposes protocol design that can do user authentication efficiently in current systems that client-server environment is developed. And proposes a password-based authentication protocol suitable to certification through trustless network or key exchange. While the existing password-base protocols certify users through certification authority (CA) between client and server, the proposed protocol in this paper, users and server exchange keys and perform authentication without help of CA. To ameliorate the drawback of password-based protocols causing by the short length and randomness of password, the proposed protocol uses the signature techniques of ECDSA and the SRP protocol based on Diffie-Hellman key exchange method. Also, by with compare to round number and Hash function number and exponential operation of existing protocols, we explained efficiency of proposed protocol.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.4
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• pp.439-446
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• 2003

In this paper, a single sign-on system has been designed and implemented. The purpose of the proposed system is that a user logs in once using a single password and gets authenticated access to all the servers that he is authorized to use without sending any passwords over the network. The proposed system involves the use of digital signature and cryptographic authentication protocols. For its implementation, a public-key infrastructure is also designed and implemented. To view the behavior of the proposed system, message sequence charts and state transition diagrams have been

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.289-292
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• 2003

네트워크에 대한 접근 용이성이 높아짐에 따라 사용자는 자신의 클라이언트 터미널 이외의 터미널로부터 네트워크에 접속하고자 하며, 이러한 로밍 유저(Roaming User)는 패스워드-기반의 인증 프로토콜을 통하여 원격의 서버로부터 비밀키와 같은 자신의 비밀정보를 다운로드 할 수 있다. 본 논문에서는 그 동안 제시되어온 로밍 프로토콜들［7,8,9］을 간략하게 살펴봄으로써, 프로토콜의 구성 방법 그리고 사전 공격 등의 패스워드-기반 프로토콜에 대한 일반적인 공격으로부터 안전하기 위하여 어떠한 암호학적 기법들을 사용하였는지 이해하고자 한다. 그리고, 이러한 프로토콜들의 암호학적 특징들에 대한 차이점을 비교 분석한다.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.11
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• pp.622-633
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• 2002

Authentication and Key Agreement using password provide convenience and amenity, but what human can remember has extremely low entropy. To overcome its defects, AMP(Authentiration and key agreement via Memorable Password) which performs authentication and key agreement securely via low entropy password are presented. AMP uses Diffie-Hellman problem that depends on discrete logarithm problem. Otherwise, this thesis applies elliptic curve cryptosystem to AMP for further efficiency That is, this thesis presents EC-AMP(Elliptic Curve-AMP) protocol based on elliptic curve discrete logarithm problem instead of discrete logarithm problem, and shows its high performance through the implementation. EC-AMP secures against various attacks in the random oracle model just as AMP Thus, we nay supply EC-AMP to the network environment that requires authentication and key agreement to get both convenience and security from elliptic curve discrete logarithm problem.