摘要:设计安全、高效的多服务器环境下匿名身份认证协议是当前安全协议领域的研究热点.基于广泛接受的攻击者模型，对多服务器环境下的3个代表性匿名认证协议进行了安全性分析.指出：（1）Wan等人的协议无法实现所声称的离线口令猜测攻击，且未实现用户匿名性和前向安全性；（2）Amin等人的协议同样不能抵抗离线口令猜测攻击，且不能提供匿名性，对两种破坏前向安全性的攻击是脆弱的；（3）Reedy等人的协议不能抵抗所声称的用户仿冒攻击和离线口令猜测攻击，且无法实现用户不可追踪性.突出强调这些协议失败的根本原因在于，违反协议设计的3个基本原则：公钥原则、用户匿名性原则和前向安全性原则.明确协议的具体失误之处，并提出相应修正方法.



Abstract:The design of secure and efficient user authentication protocols for multi-server environment is becoming a hot research topic in the cryptographic protocol community. Based on the widely accepted adversary model, this paper analyzes three representative, recently proposed user authentication schemes for multi-server environment. The paper reveals that:(1) Wan, et al.'s scheme is subject to offline password guessing attack as opposed to the authors' claim, and it also cannot provide user anonymity and forward secrecy; (2) Amin, et al.'s scheme cannot withstand offline password guessing attack, cannot preserve user anonymity and is vulnerable to two kinds of forward secrecy issues; (3) Reedy, et al.'s scheme cannot resist against user impersonation attack and offline password guessing attack, and also falls short of user un-traceability. The paper highlights three principles for designing more robust anonymous multi-factor authentication schemes:Public key principle, user anonymity principle and forward secrecy principle, explaining the essential reasons for the security flaws of the above protocols. It further proposes some amendments for the identified security flaws.



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