基于椭圆曲线的跨域端到端口令认证密钥协商协议

跨域端到端口令认证密钥协商协议(C2C-PAKA)的主要目的是使分布在不同域中持有不同口令的两个客户端可以在各自服务器的协助下实现相互认证并协商出共同的会话密钥。本文中,我们基于椭圆曲线上的离散对数问题,在直接通信架构下给出一个跨域的口令认证的密钥协商协议。该协议中,诚实的服务器是不能获取任何关于会话密钥的值。各参与方之间能够实现相互认证。与同类协议比较,该协议具有较小的通信负担和计算负担,更易于实现。此外,协议还能够抵抗字典攻击、口令泄露模仿攻击和未知会话密钥共享攻击等通用攻击类型,同时能够实现前向安全、无密钥控制和已知会话密钥安全等安全属性。     

基于自验证公钥的跨域口令认证密钥协商协议

结合自验证公钥密码学和口令构造了一个用户可以直接通信的跨域口令认证密钥协商协议。域服务器通过口令认证实现对域内用户的认证, 并与对方域服务器一起协助用户完成认证和密钥协商。该过程中, 域服务器不能获取关于会话密钥的任何信息, 且各参与方之间能够实现相互认证。与同类协议相比, 该协议需要较小的计算和通信代价, 并能抵抗字典攻击和未知会话密钥共享攻击。     

基于二次剩余的多服务器环境下的身份认证协议

多服务器环境下的身份认证协议实现了用户只需要一次注册即可跟多个服务器实现交互认证,基于二次剩余构造了一个注册中心在线的多服务器环境下身份认证协议。该协议中,注册中心参与实现对用户的认证并协助用户和服务器建立后继通信的会话密钥,并且服务器之间是可以相互区分的。协议能够抵抗字典攻击、口令泄露模仿攻击常见攻击,同时能够实现相互认证,以及前向安全、已知会话密钥安全和无密钥控制等会话密钥的安全属性。     

基于椭圆曲线的加密密钥交换协议

加密密钥交换协议(EKE)的目的是利用安全性低的口令协商安全性高的密钥,进而利用密钥对以后的通信进行加密或身份认证,从而实现安全通信.基于验证元的EKE是针对服务器泄露攻击问题提出的.本文基于椭圆曲线密码系统的特点,给出了一个基于验证元的3EKE,该协议中,服务器通过口令实现对用户的认证;协议能够抵抗服务器泄露等攻击,...     

基于验证元的三方口令认证密钥交换协议

三方口令认证密钥交换协议使2个分别与可信服务器共享不同口令的用户建立起秘密的会话密钥.这类协议的优点是用户只需要记忆一个口令就可以与其他注册用户进行通信,因而三方口令认证密钥交换协议更适用于大规模的端到端通信.现有的大多数三方口令认证密钥交换协议均基于随机谕言模型来实现,只有少数协议不依赖服务器拥有公钥,而且在标准模型下是可证明安全的.另外多数协议中的口令以明文的形式存储在服务器上,服务器信息泄露将对用户和服务器的数据安全带来极大的危害.在标准模型下,使用平滑投影Hash函数设计了一个基于验证元的三方口令认证密钥交换协议,并证明了协议的安全性.此协议满足抵抗服务器泄露、不可检测的在线字典攻击和密钥私密性等安全属性.     

IKEv2协议的分析与改进

IKEv2协议中的预共享密钥认证方式容易受到中间人攻击和离线字典攻击,从而泄漏发起方的身份信息和通信双方的预共享密钥。针对上述2种攻击,提出将数字签名认证方式与预共享密钥认证方式相结合的防御措施,引入公钥口令的思想,避免建立公钥基础设施带来的额外负担。分析结果表明,改进后的协议能够避免中间人攻击和离线字典攻击,防止通信双方身份的泄漏和预共享密钥的破解。     

一个强安全性的三方密钥交换协议

先对一个基于验证元的三方密钥交换协议进行安全性分析,指出其容易受到服务器泄露攻击等安全威胁,并以此为基础提出一个改进的密钥交换协议。通过安全性分析,证明该协议能够抵御服务器密钥泄露攻击﹑离线字典攻击等各种已知的攻击,且与其他同类协议相比,新协议具有较高的效率。     

基于百万富翁算法的口令认证密钥交换协议

口令认证密钥交换（PAKE）协议由于其便于记忆、运行成本低等特点受到广泛关注。文章在百万富翁协议算法的基础上,通过简化和改进,提出一种口令认证的密钥交换协议。该协议使用一个低熵的口令进行双方的认证,并得到一个高熵的密钥。文章同时分析了该协议对抵御中间人攻击和离线字典攻击的安全性。     

对两个口令认证密钥交换协议的安全性分析

口令认证密钥交换协议使得仅共享低熵口令的用户可以通过不安全的信道安全地协商出高熵的会话密钥,由于实用性较强受到了密码学研究者的广泛关注。对最近在“标准模型下高效的基于口令认证密钥协商协议”一文中提出的协议以及在“基于验证元的三方口令认证密钥交换协议”一文中提出的协议进行了分析,指出这两个口令认证密钥交换协议都是不安全的,难于抵抗离线字典攻击,进一步分析了原协议设计或安全性证明中被疏忽之处。     

一种可证安全的两方口令认证密钥交换协议

口令认证的两方密钥交换协议无法抵御口令字典攻击和服务器泄漏伪装攻击。为此,提出一种改进的PAKA-X协议,用户保存自己的口令明文,服务器存储用户口令明文的验证值,由此弥补原协议的安全漏洞。理论分析结果表明,改进协议具有完美前向安全性,能抵抗Denning-Sacco攻击、服务器泄漏攻击、在线和离线字典攻击以及中间人攻击,并且仅需9次指数运算、6次哈希运算和6次异或运算,运行效率较高。     

Cryptanalysis of simple three-party key exchange protocol

Recently, Lu and Cao published a novel protocol for password-based authenticated key exchanges (PAKE) in a three-party setting in Journal of Computers and Security, where two clients, each shares a human-memorable password with a trusted server, can construct a secure session key. They argued that their simple three-party PAKE (3-PAKE) protocol can resist against various known attacks. In this paper, we show that this protocol is vulnerable to a kind of man-in-the-middle attack that exploits an authentication flaw in their protocol and is subject to the undetectable on-line dictionary attack. We also conduct a detailed analysis on the flaws in the protocol and provide an improved protocol.     

Provably secure three-party password authenticated key exchange protocol in the standard model

Three-party password authenticated key exchange protocol is a very practical mechanism to establish secure session key through authenticating each other with the help of a trusted server. Most three-party password authenticated key exchange protocols only guarantee security in the random oracle model. However, a random oracle based cryptographic construction may be insecure when the oracle is replaced by real function. Moreover, some previous unknown attacks appear with the advance of the adversary capability. Therefore, a suitable standard model which can imitate a wider variety of attack scenarios for 3PAKE protocol is needed. Aim at resisting dictionary attack, unknown key-share attack and password-compromise impersonation attack, an expanded standard model for 3PAKE protocol is given. Meanwhile, through applying ElGamal encryption scheme and pseudorandom function, a specific three-party password authenticated key exchange protocol is proposed. The security of the proposed protocol is proven in the new standard model. The result shows that the present protocol has stronger security by comparing with other existing protocols, which covers the following security properties: (1) semantic security, (2) key privacy, (3) client-to-server authentication, (4) mutual authentication, (5) resistance to various known attacks, and (6) forward security.     

改进的三方口令验证元认证密钥交换协议

在三方口令认证密钥交换(三方PAKE)协议中,每个用户仅仅需要和服务器共享一个口令,就可以在服务器的协助下与他人进行安全的密钥交换.由于有效地减少了用户管理口令的负担,三方PAKE协议在大规模用户集的安全通信中受到了较多关注.然而,已有的三方PAKE协议大多关注的是服务器利用明文存储用户口令的情形,没有考虑服务器口令文件泄露所造成的巨大威胁.在服务器端存放的是相应于用户口令的验证元的情形下,研究三方PAKE协议的分析和设计.首先分析了一个最近提出的基于验证元的三方PAKE协议,指出该协议易于遭受离线字典攻击,因此未能达到所宣称的安全性;其次,在分析已有协议设计缺陷的基础上,提出了一个新的基于验证元的三方PAKE协议,并在标准模型下证明了所设计的协议的安全性,与已有协议的比较表明,新提出的协议在提供了更高安全性的同时具有可接受的计算和通信效率.     

基于ECDSA的三方口令认证密钥交换协议

提出一种基于椭圆曲线数字签名算法(ECDSA)的三方口令认证密钥交换协议。将ECDSA分为公钥生成、签名过程和验证过程 3个阶段,在此基础上,设计协议过程、双向认证机制,使任意2个用户通过服务器能进行身份认证和密钥交换。分析结果表明,该协议能降低计算难度和存储开销,抵抗字典攻击和服务器泄露攻击。     

Password-authenticated key exchange based on RSA

There have been many proposals in recent years for password-authenticated key exchange protocols, i.e., protocols in which two parties who share only a short secret password perform a key exchange authenticated with the password. However, the only ones that have been proven secured against offline dictionary attacks were based on Diffie–Hellman key exchange. We examine how to design a secure password-authenticated key exchange protocol based on RSA. In this paper, we first look at the OKE and protected-OKE protocols (both RSA-based) and show that they are insecure. Then we show how to modify the OKE protocol to obtain a password-authenticated key exchange protocol that can be proven secure (in the random oracle model). This protocol is very practical; in fact, it requires about the same amount of computation as the Diffie–Hellman-based protocols. Finally, we present an augmented protocol that is resilient to server compromise, meaning (informally) that an attacker who compromises a server would not be able to impersonate a client, at least not without running an offline dictionary attack against that client’s password.     

Security weakness in a three-party pairing-based protocol for password authenticated key exchange

Authentication and key exchange are fundamental for establishing secure communication channels over public insecure networks. Password-based protocols for authenticated key exchange are designed to work even when user authentication is done via the use of passwords drawn from a small known set of values. Recently, Wen et al. (H.-A. Wen, T.-F. Lee, T. Hwang, Provably secure three-party password-based authenticated key exchange protocol using Weil pairing, IEE Proceedings—Communications 152 (2) (2005) 138-143) proposed a new protocol for password-based authenticated key exchange in the three-party setting, where the clients trying to establish a common secret key do not share a password between themselves but only with a trusted server. Wen et al.’s protocol carries a claimed proof of security in a formal model of communication and adversarial capabilities. However, this work shows that the protocol for three-party key exchange is completely insecure and the claim of provable security is seriously incorrect. We conduct a detailed analysis of flaws in the protocol and its security proof, in the hope that no similar mistakes are made in the future.     

A secure and efficient identity-based authenticated key exchange protocol for mobile client–server networks

Recently, Chou et al. (J Supercomput 66(2): 973–988, 2013) proposed two identity-based key exchange protocols using elliptic curves for mobile environments. The first one is an two-party authentication key exchange protocol to establish a session key between a client and a remote server. The second one is an extended version for three-party setting to establish a session key between two clients with the help of a trusted server. However, this paper finds the first one vulnerable to impersonation attack and key-compromise impersonation attack, and the second one insecure against impersonation attack. To overcome the weaknesses, we propose an improved identity-based two-party authentication key exchange protocol using elliptic curves. The rigorous analysis shows that our scheme achieves more security than related protocols.