普适计算环境下的主动模糊访问控制技术研究

【作者】 窦文阳；

【导师】 王小明；

【作者基本信息】 陕西师范大学 ， 计算机软件与理论， 2013， 博士

【摘要】 随着移动设备、智能手机和传感器技术的迅速发展,普适计算正日益走进人们的日常生活。普适计算的重要特点之一是计算机及信息系统能够感知物理世界的变化,从而对其行为做出主动调整,以更好地服务人类。换句话说,计算机系统通过感知和分析来自物理世界的信息而变得更加智能。人类社会、信息空间、物理世界三者的全面连通与融合正成为下一代普适计算技术的重要特征和主要趋势。随着人们对普适计算研究的不断深入,普适计算环境下的安全问题(如信息的保密性、完整性、可用性和隐私性等)成为研究关注的焦点,同时也是阻碍普适计算从理论和实验阶段走向大规模实际应用的主要问题之一。由于普适计算具有分布性、动态性和不确定性等特点,传统的安全技术难以满足其复杂的安全需求。访问控制作为保障计算机安全的核心技术之一,对复杂信息系统的安全控制十分有效,因此也必将成为确保普适计算安全的关键技术。现有访问控制技术普遍采取的是集中安全策略管理模式和基于确定信息(包括安全策略、主体身份等)的静态授权方式,这种封闭环境下被动的访问控制已经无法适用于具有高度开放性的普适计算环境,迫切需要研究一种全新的访问控制技术。本文针对普适计算环境下资源的安全访问控制问题进行了研究。论文将主动数据库理论、元图理论、模糊集合理论、模糊控制和模糊推理方法引入了传统访问控制技术,从访问控制的策略、模型和实现机制三个层面上对普适计算环境下的主动模糊访问控制技术进行了系统深入研究,解决了普适计算环境下访问控制的模糊不确定性和动态自适应性问题,为下一代智能访问控制技术研究提供了新的思路。论文的主要工作如下：1.提出了一个普适计算环境下的模糊访问控制模型。该模型针对普适计算环境下具有不确定性的上下文信息和模糊信任关系建立模型,并引入授权决策过程。在该模型中,用户最终权限的获取是通过对上下文条件的满足程度、用户的信任程度以及激活角色可能产生的安全风险进行模糊推理得到的。给出了模型实现的体系结构,对模糊授权推理器的设计与实现进行了详细说明。2.提出了一个普适计算环境下的主动访问控制模型。该模型将空间角色、环境及安全强度等概念引入访问控制模型建模,实现了在不同的安全强度下,用户可以激活不同的角色和使用不同的权限。基于主动数据库技术的ECA规则触发机制,设计了模型的主动访问控制模式,即根据环境上下文变化主动提供授权服务,并且自适应地调整模型的安全控制强度和授权策略。3.提出了一种基于区间值主动模糊规则的主动模糊访问控制模型。首先将区间值模糊集合理论和主动数据库技术引入访问控制规则建模,提出了一种主动区间值模糊访问控制规则,用以描述普适计算环境下具有主动性和模糊不确定性的安全控制策略；然后基于提出的区间值主动模糊访问控制规则,构造了一个普适计算环境下的主动模糊访问控制模型,该模型具有支持多安全策略、分布式授权等特点；最后给出了保证访问控制模型授权正确性和可信性的条件,即保证主动模糊访问控制规则集的终止性和汇流性。4.提出了一种基于元图理论的主动模糊访问控制规则集终止性分析方法。首先给出了模糊触发元图(Fuzzy Triggering Metagraph, FTMG)定义,用以表示主动模糊访问控制规则之间复杂的触发和激活关系；然后给出了一个基于FTMG的主动模糊访问控制规则集终止性分析方法,即通过分析FTMG的邻接矩阵闭包,寻找最小真触发环,判断主动模糊访问控制规则集的终止性；最后通过一个实例详细说明了算法的具体分析过程,并验证了该方法的正确性。5.提出了一种基于元图理论的主动模糊访问控制规则集汇流性分析方法。首先给出了主动模糊访问控制规则集汇流性的定义,然后提出了一个基于FTMG的主动模糊访问控制规则集汇流性分析方法,并给出了相关的定理、证明及算法；最后通过一个实例详细说明了算法的具体分析过程,并验证了该方法的正确性。6.设计并实现了一个普适计算环境下的智能访问控制原型系统(Smart Access Control System, SACS)。首先给出了SACS系统的体系结构设计及授权流程,然后对访问控制相关模块的设计与实现进行了详细说明,并给出了相关实现算法和部分实现代码；最后通过仿真实验测试了SACS原型系统的运行效率,通过对比实验验证了本文提出的基于元图的主动模糊访问控制规则集终止性分析算法具有较好的正确性和较高的效率。更多还原

【Abstract】 With the development of mobile device, smart phone and sensor technology, ubiquitous computing is entering into people’s lives. One of the important features of ubiquitous computing is that the computers are able to perceive the changes in the physical world, and make the initiative to adjust their behavior and provide better services for people. In other words, the computers become more intelligent through the perception and analysis of the contexts from the physical world, therefore, the connectivity and integration of human society, information space and physical world is becoming the important feature of the next generation of the ubiquitous computing technology, and the ubiquitous computing will provide a harmonious environment with more transparent, more intelligent, greener and more secure services.With the deepening of the pervasive computing research, which the security issue becomes a focus problem (such as the confidentiality, integrity, availability and privacy of the information), at the same time, it is one of the main problem to hinder the pervasive computing to large-scale practical application from the theoretical and experimental stage; on the other hand, the traditional security mechanism is difficult to meet the security needs of the complex environment of pervasive computing, as the pervasive computing has the characteristics of distributed, dynamic, uncertainty. So, the access control is one of the kernel technology to protect computer security, and it is very effective to the security control of complex information systems, and it will also become the key technology to ensure secure of pervasive computing. However, the existing access control generally adopt centralized security policy management mode and determined information (including security policy, subject identity) based static authorization, such passive access control in the closed environment, is no longer applicable to highly open pervasive computing environment. To achieve a safe and effective control of resources in the pervasive computing environment, it is necessary to establish a new access control mechanism:the established new mechanism not only be able to trigger specific events in the ubiquitous environment, take the initiative to adjust the authorization policy changed adaptively control strength to ensure the safety and flexibility of permissions; but also it can support the authorization inference between the uncertain context information and fuzzy trust relationship, and give the result of the determininged authorization decision to ensure the correctness and intelligence of the authorization process. As the energy of the pervasive equipment is limited, the performance of access control system is higher, therefore, the access control system in pervasive computing environment shoule not only ensure the correctness and confluence of authorization inference results, and also prevent invalid circular reasoning, in order to guarantee the termination of the authorization decision process.In this paper, to address the problem of access control in pervasive computing environment, we propose an active fuzzy access control method.and its realization mechanism used in pervasive computing environment, which is analyzed deeply the dynamic behavior of the access control system. In the proposed method, the active database theory, metgraphs theory, interval-valued fuzzy set theory, interval-valued fuzzy inference method and fuzz control technology are introduced into the traditional access control technology, and the active fuzzy access control technology is studied from three aspects:access control strategy, model and mechanism, which solve the fuzzy uncertainty and dynamic adaptive of pervasive computing, and provide a new idea for smart access control system. The mainly works of the paper are as follows:(1) A fuzzy access control model for ubiquitous computing is presented, which is established to uncertainty context information and fuzzy trust relationship, and the authorization decision process is also introduced to this model. Furthermore, the permission of the user is obtained by the fuzzy inference of the satisfaction degree of the context condition, the level of trust of the user and the risk of the user’s role activate. At last, the architecture of model and the design of fuzzy inference machine are detailed presented.(2) An active access control model for ubiquitous computing is presented, which is established by introducing the space role, environment role and security level, to realize the user can active the different roles and use the different permissions under different security level. Moreover, an active access control mode is designed based on the trigger mechanism of ECA rules, That is, the model can initiative to adjust the access control level and security control strategy according to the changes in the context, to realize an adaptive control for resources.(3) An active fuzzy access control model for ubiquitous computing is presented. Firstly, the interval-valued fuzzy set theory and active database technology is introduced into access control rule model, and an active interval-valued fuzzy access control rule is presented to describe the active fuzzy security strategy of pervasive computing environment; secondly, an active fuzzy access control model based on active interval-valued fuzzy access control rule is presented; finally,the termination and confiluence analysis problems of active fuzzy access control rule set is presented.(4) A termination analysis method based on metgraph theory for active fuzzy access control rules set is presented. Firstly, the concept of termination is given; secondly, a termination analysis method based on fuzzy trigger metgraph is presented, and the theorem and algorithm are presented; Finally, the simulation results demonstrate that the accuracy and efficiency of the proposed method.(5) A confluence analysis method based on metgraph theory for active fuzzy access control rules set is presented. Firstly, the concept of confluence is given; secondly, a confluence analysis method based on fuzzy trigger metgraph is presented, and the theorem and algorithm are presented; lastly, an example show the specific analysis procedure.(6) A prototype system of smart access control is designed and implemented. System architecture is presented, fuzzy reasoning efficiency is proved. Firstly, the architecture design and authorization process of the SACS are given; and then, the details of realizing the access control module are explained; finally, we compare the efficiency of the prototype system to the termination analysis of the access control rules set.更多还原