• Review of KIISC
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• v.28 no.1
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• pp.29-35
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• 2018

Passphrases are considered to be more secure than passwords since they are longer than passwords. However, users choose predictable word patterns and common phrases to make passphrases memorable, which in turn significantly lowers security. While random passphrases appear to be stronger, surprisingly they are neither strong nor memorable. In this paper, we present the latest passphrase research, and introduce a new way to create a passphrase using mnemonics. Passphrase generation using mnemonics shows promising results in improving both strength and memorability.

• Journal of KIISE:Software and Applications
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• v.31 no.9
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• pp.1218-1225
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• 2004

S/KEY system was proposed to guard against intruder's password replay attack. But S/KEY system has vulnerability that if an attacker derive passphrase from his dictionary file, he can acquire one-time password required for user authentication. In this paper, we propose a correct S/KEY system mixed with EKE to solve the problem. Also, we specify a new S/KEY system with Casper and CSP, verify its secrecy and authentication requirements using FDR model checking tool.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.715-717
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• 2001

네트워크 컴퓨팅 시스템에서 생길 수 있는 공격유형중의 하나는 로그인 아이디, 패스워드와 같은 인증정보를 네트워크상에서 가로채는 것이다. 이러한 정보를 일단 획득하면 후에 언제든지 이용할 수 있게 되는 것이다. 일회용 패스워드 시스템은 이러한 “재공격(replay attack)”을 방어하기 위해 Bellcore사에 의해 고안되어졌다. 하지만 이 인증 시스템은 취약점을 가지고 있는데 만일 공격자가 자신이 가지고 있는 사전에서 passphrase를 유추해 낼 수 있다면 결국 SKEY의 결과값인 일회용 패스워드까지 알아낼 수 있게 된다. 따라서 이 passphrase를 보다 안전하게 사용자와 시스템간에 전달할 수 있게 하기 위해 EKE(Extended Key Exchange) 프로토콜을 사용하여 키의 스니퍼링 뿐만 아니라 dictionary attack을 방지하고자 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.349-357
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• 2017

Many Web sites adopt SMS(Short Message Service)-based user authentication when a user loses her password or approves an online payment. In SMS-based authentication, the authentication server sends a text in plaintext to a user's phone, and it allows an attacker who eavesdrops or intercepts the text to impersonate a valid user(victim). We propose a challenge-response scheme to prove to the authentication server that a user is in a certain place at the moment with her smartphone beside her. The proposed scheme generates a response using a challenge by the server, user's current location, and a secret on the user's smartphone all together. Consequently, the scheme is much more secure than SMS-based authentication that simply asks a user to send the same text arrived on her phone back to the server. In addition to entering the response, which substitutes the SMS text, the scheme also requests a user to input a passphrase to get the authentication process started. We believe, however, the additional typing should be tolerable to most users considering the enhanced security level of the scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.10
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• pp.2844-2861
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• 2023

Internet is the most prevailing word being used nowadays. Over the years, people are becoming more dependent on the internet as it makes their job easier. This became a part of everyone's life as a means of communication in almost every area like financial transactions, education, and personal-health operations. A lot of data is being converted to digital and made online. Many researchers have proposed different authentication factors - biometric and/or non-biometric authentication factors - as the first line of defense to secure online data. Among all those factors, passwords and passphrases are being used by many users around the world. However, the usability of these factors is low. Also, the passwords are easily susceptible to brute force and dictionary attacks. This paper proposes the generation of a novel passcode from the hybrid authentication factor - sound. The proposed passcode is evaluated for its strength to resist brute-force and dictionary attacks using the Shannon entropy and Passcode (or password) entropy formulae. Also, the passcode is evaluated for its usability. The entropy value of the proposed is 658.2. This is higher than that of other authentication factors. Like, for a 6-digit pin - the entropy value was 13.2, 101.4 for Password with Passphrase combined with Keystroke dynamics and 193 for fingerprint, and 30 for voice biometrics. The proposed novel passcode is far much better than other authentication factors when compared with their corresponding strength and usability values.