In this paper, a general framework for designing and analyzing password-based security protocols is presented. First we introduce the concept of ＂weak computational indistinguishability＂ based on current progress of password-based security protocols. Then, we focus on cryptographic foundations for password-based security protocols, i.e., the theory of ＂weak pseudorandomness＂. Furthermore, based on the theory of weak pseudorandomness, we present a modular approach to design and analysis of password-based security protocols. Finally, applying the modular approach, we design two kinds of password-based security protocols, i.e., password-based session key distribution （PSKD） protocol and protected password change （PPC） protocol. In addition to having forward secrecy and improved efficiency, new protocols are proved secure.
Ad Hoc网是一种不依赖于任何固定基础设施、没有中心控制节点、计算资源受限的新型无线移动网络.最近王晓峰等学者提出了一个新的适用于Ad Hoc网的具有口令认证和共享口令进化的多方密钥协商协议,并认为他们的协议是安全而高效的.然而我们发现这一协议存在严重的安全缺陷:不能抵抗离线口令猜测攻击和伪造攻击;不能提供前向安全性和后向安全性;不能动态更新群组成员的密钥.
