信息安全技术讲座 第3讲 口令认证与口令管理

口令方式仍是当前许多计算机网络系统的安全防范措施中广泛采用的一种，然而，随着网络规模的扩大，口令管理成了系统安全提升的一个瓶颈。本文通过对目前用于用户身份认证和访问控制的口令认证机制进行分析，结合国内，国际一些先进的口令管理产品，提出一些参考性的解决方案。     

改进的无证书有序多重签名方案

A sequential multi-signature enabled multiple users to jointly sign a document in order.Xu,et al proposed a provably-secure certificateless sequential multi-signature scheme with constant signature length and pairing computations.However,it was shown that the scheme had a drawback in the verifying algorithm,and then it overcame the drawback.But,the efficiency of the corrected scheme was greatly reduced.An efficient certificateless sequential multi-signature scheme is constructed,and the multi-signature generated by proposed scheme consists of one group element and the verification algorithm requires only 2 bilinear pairings.     

优化MISTY型结构的伪随机性

该文对4轮MISTY和3轮双重MISTY两种结构进行了优化。在保持其安全性不变的情况下,把4轮MISTY结构中第1轮的伪随机置换,用一个XOR-泛置换代替,第2,第3轮采用相同的伪随机置换,3轮结构中第1轮的伪随机置换用XOR-泛置换代替,其它轮相同。伪随机置换的数量分别由原来的4个变为2个,3个变为1个,从而缩短了运行时间,节省了密钥量,大大降低了结构的实现成本。     

RBAC角色继承关系中私有权限问题的研究

角色的私有权问题一直是RBAC中没有解决的问题。在分析现有的私有权解决方案的基础上,提出了角色的N阶继承方法,将角色的权限分为私有、保护和公有三类,对保护权限的继承进行了定义。为了能够将一个角色的非私有权限继承为私有权限,又提出了三种不同的继承模式:Private模式、Protected模式和Public模式。     

An efficient two-step quantum key distribution protocol with orthogonal product states

An efficient two-step quantum key distribution (QKD) protocol with orthogonal product states in the n\otimes n(n\geq3)Hilbert space is presented. In this protocol, the particles in the orthogonal product states form two particle sequences. The sender, Alice, first sends one sequence to the receiver, Bob. After Bob receives the first particle sequence, Alice and Bob check eavesdropping by measuring a fraction of particles randomly chosen. After ensuring the security of the quantum channel, Alice sends the other particle sequence to Bob. By making an orthogonal measurement on the two particle sequences, Bob can obtain the information of the orthogonal product states sent by Alice. This protocol has many distinct features such as great capacity, high efficiency in that it uses all orthogonal product states in distributing the key except those chosen for checking eavesdroppers.     

5元1-弹性函数的代数免疫阶

首先给出了最优代数免疫布尔函数弹性阶的一个上界,并且证明了一类5元1阶弹性函数不是最优代数免疫函数,得到了最优代数免疫函数具有一阶弹性时可能的结构形式;在此基础上,给出了布尔函数代数免疫阶和弹性阶随着变元个数变化的一些结果,最后给出了一个5元1阶弹性的最优代数免疫布尔函数。     

保密多方量子求和

给出基于非正交态的量子保密模加法方案，允许累加者把一个数保密地累加在一个未知数上.提出的保密多方量子求和方案对于窃取者是渐进安全的，n-1方的共谋攻击不会使得另一方泄露全部信息.     

Threshold Quantum Secret Sharing of Secure Direct Communication

We propose a （L, n）-threshold quantum secret sharing protocol of secure direct communication following some ideas of Zhang＇s protocol [Phys. Lett. A 342 （2005） 60] and Tokunaga et al.＇s protocol [Phys. Rev. A 71 （2005） 012314]. The sender distributes the classical secret shares to his or her n agents and each agent owns a secret share in advance. The sender＇s secure direct communication message can be extracted by an agent subset by collaboration in such a way that at least t or more agents can obtain the secret message with the mutual assistances but any t - 1 or fewer agents cannot. In contrast to the previous multiparty quantum secret sharing protocols in which the sender＇s secret message can be recovered only if all the agents collaborate, our protocol is more practical and more flexible.     

Fair quantum blind signatures

We present a new fair blind signature scheme based on the fundamental properties of quantum mechanics. In addition, we analyse the security of this scheme, and show that it is not possible to forge valid blind signatures. Moreover, comparisons between this scheme and public key blind signature schemes are also discussed.     

Robust Quantum Secure Direct Communication over Collective Rotating Channel

A quantum secure direct communication protocol over a collective rotating channel is proposed. The protocol encodes logical bits in noiseless subspaces, and so it can function over a quantum channel subjected to an arbitrary degree of collective rotating noise. Although entangled states are used, both the sender and receiver are only required to perform single-particle product measurement or Pauli operations. The protocol is feasible with present-day technique.