关于离散随机变量熵的一个上界

本文分析了离散随机变量熵与方差及有关微分熵的某种关系，给出了离散随机变量熵的一个上界，改进了Ｔ．Ｍ．Ｃｏｖｅｒ与Ｊ．Ａ．Ｔｈｏｍａｓ关于离散熵的上界的已有结果［１］，并以图和表的方式举出一些实例加以比较。     

一种虚拟机系统下关于多级安全的强制访问控制框架II:实现

This paper is a continuation of our last paper [1] which describes the theory of Virt-BLP model. Based on Virt-BLP model, this paper implements a mandatory access control (MAC) framework applicable to multi-level security (MLS) in Xen. The Virt-BLP model is the theoretical basis of this MAC framework, and this MAC framework is the implementation of Virt-BLP model. Our last paper focuses on Virt-BLP model, while this paper concentrates on the design and implementation of MAC framework. For there is no MAC framework applicable to MLS in virtual machine system at present, our MAC framework fills the blank by applying Virt-BLP model to Xen, which is better than current researches to guarantee the security of communication between virtual machines (VMs). The experimental results show that our MAC framework is effective to manage the communication between VMs.     

与经典信道相关的网络编码

传统的网络信息流传输方式是存储转发,但通常无法达到通信的最大流界。为了实现更高的传输效率,Ahlswede等人提出采用网络编码的方法,不但可以提高网络吞吐量,而且在普适性、鲁棒性、可靠性和安全性等方面都具有优势。网络中的信道通常是有噪声的,目前网络编码理论的研究重点包括经典多用户信道、网络-信道编码分离和网络安全编码等问题。     

推荐系统中基于无监督策略托攻击检测﹡

协同过滤推荐系统中,推荐结果对用户偏好信息的敏感性使得推荐系统易受到人为攻击,即托攻击.恶意用户可以任意使用多重身份,或者是多个人来参与,都能注入恶意信息到推荐系统中.这类攻击严重影响了推荐系统的鲁棒性和准确性.这里深入分析了托攻击,结合主成分分析和变量选择方法,提出一个高精确度鲁棒的协同过滤系统架构,以保护推荐系统抵御用户概貌注入攻击.最后,通过实验验证表明该新型的高精确度的协同过滤系统可以取得更好的检测精度.     

一种虚拟机系统中关于多级安全的强制访问控制框架Ⅰ：理论

At present, there are few security models which control the communication between virtual machines (VMs). Moreover, these models are not applicable to multi-level security (MLS). In order to implement mandatory access control (MAC) and MLS in virtual machine system, this paper designs Virt-BLP model, which is based on BLP model. For the distinction between virtual machine system and nonvirtualized system, we build elements and security axioms of Virt-BLP model by modifying those of BLP. Moreover, comparing with BLP, the number of state transition rules of Virt-BLP is reduced accordingly and some rules can only be enforced by trusted subject. As a result, Virt-BLP model supports MAC and partial discretionary access control (DAC), well satisfying the requirement of MLS in virtual machine system.As space is limited, the implementation of our MAC framework will be shown in a continuation.     

F2上第三类向量深度的分布及序列{(E-1)m(s)}m≥0的周期

向量复杂程度的一个研究角度是向量的深度.将Etzion和Roth提出的向量深度归纳为3类向量深度,通过有限长序列的周期与第三类向量深度之间的关系,给出了F2上任意n维向量空间的第三类向量深度的分布,并且利用向量算子的矩阵描述,从序列{(E-1)m(s)}m≥0终归周期的角度,进一步考察了第三类向量深度为∞的向量的性质.