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Authentication schemes have been widely deployed access control and mobility management in various communication networks. Especially, the schemes that are based on multifactor authentication such as on password and smart card come to be more practical. One of the standard authentication schemes that have been widely used for secure communication over the Internet is session initiation protocol (SIP). The original authentication scheme proposed for SIP was vulnerable to some crucial security weaknesses. To overcome the security problems, various improved authentication schemes have been developed, especially based on elliptic curve cryptography (ECC). Very recently, Zhang et al. proposed an improved authentication scheme for SIP based on ECC using smart cards to overcome the security flaws of the related protocols. Zhang et al. claimed that their protocol is secure against all known security attacks. However, this paper indicates that Zhang et al. protocol is still insecure against impersonation attack. We show that an active attacker can easily masquerade as a legal server to fool users. As a remedy, we also improve Zhang et al. protocol by imposing a little extra computation cost. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we first showed that Lou and Huang's three-party password-based key exchange protocol is still vulnerable to offline dictionary attacks. Thereafter, we proposed an enhanced protocol that can defeat the attack described and yet is efficient. Finally, we provided the rigorous proof of the security for it. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Password-authenticated group key exchange protocols enable communication parties to establish a common secret key (a session key) by only using short secret passwords. Such protocols have been receiving significant attention. This paper shows some security weaknesses in some recently proposed password-authenticated group key exchange protocols. Furthermore, a secure and efficient password-authenticated group key exchange protocol in mobile ad hoc networks is proposed. It only requires constant round to generate a group session key under the dynamic scenario. In other words, the overhead of key generation is independent of the size of a total group. Further, the security properties of our protocol are formally validated by a model checking tool called AVISPA. Security and performance analyses show that, compared with other related group key exchange schemes, the proposed protocol is also efficient for real-world applications in enhancing the security over wireless communications. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Three-party password-authenticated key exchange (3PAKE) protocols allow entities to negotiate a secret session key with the aid of a trusted server with whom they share a human-memorable password. Recently, Lou and Huang proposed a simple 3PAKE protocol based on elliptic curve cryptography, which is claimed to be secure and to provide superior efficiency when compared with similar-purpose solutions. In this paper, however, we show that the solution is vulnerable to key-compromise impersonation and offline password guessing attacks from system insiders or outsiders, which indicates that the empirical approach used to evaluate the scheme's security is flawed. These results highlight the need of employing provable security approaches when designing and analyzing PAKE schemes. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In 2009, Huang ( Int. J. Commun. Syst., 22, 857-862) proposed a simple and efficient three-party password-based key exchange protocol without server's public key. This work shows that the protocol could be vulnerable to an undetectable online password guessing attack. Furthermore, an improved protocol is proposed to avoid the attack. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]