一种访问权限管理的格模型

描述了一种以格为基础的访问控制模型,与访问对象相关的访问权限用格的结点表示,访问权限的变化映射在格上成为一个结点到另一个结点的变换。在这种模型中,访问控制策略实时更新的并发控制算法简单且易于实现。在并发环境中,多个主体读写数据和修改访问控制策略并互相影响时,可直接应用文中的模型与算法。     

基于环境属性的访问控制系统设计与实现

目前研究的访问控制机制大多将访问策略与主客体相关联,访问权限相对固定,但在实际应用中,访问控制权限需要根据服务环境变化而实时调整。为此,构建一种基于环境属性的访问控制模型,在Linux系统下设计并实现基于该模型的访问控制系统。在访问控制的判定过程中增加环境属性因素,实现根据环境属性动态调整访问控制权限。测试结果表明,该模型对系统开销少,不会降低Linux平台的正常运行效率,能有效提升系统的安全性和可用性。     

基于区块链和策略分级的访问控制模型

为应对当前访问控制动态变化、策略合约安全性以及策略检索效率的需求,以属性访问控制模型(ABAC)为基础,提出一种基于区块链和策略分级访问控制模型BP-ABAC。结合ABAC和区块链技术,使访问控制策略通过智能合约的方式储存在区块链,合约中对访问控制策略进行策略分级;用户根据等级评估获得相应策略集的访问权限;当请求属性和策略集中的策略相匹配时,获得访问资源权限。实验结果表明,该模型实现了对不同用户访问权限控制和提高访问控制的效率与灵活性,加强了访问控制策略的安全性和隐私性。     

基于角色的Web服务的授权与访问控制

提出了一个授权与访问控制系统的设计，它以PMI为基本架构，分为授权服务和访问控制两个子系统，权限管理子系统通过各种模块制定全局所需的各种策略，由AA／SOA签发各种策略属性证书；管理员通过注册服务器ARA，为用户分配权限，向AA申清签发用户的属性证书．在访问控制子系统中，策略决策实施点(AEF)截获用户的访问请求及用户身份并发送给访问控制决策点中的ADF，ADF根据权限管理子系统制定好的策略和用户的属性证书计算出用户被授予的访问权限，作出“允许／拒绝”的决策。这样就实现了对Web资源的授权与访问控制，保证了后端Web服务器上共享数据的安全。     

基于量化行为的实时数据库备份系统访问控制模型

实时备份系统对访问行为动态性具有较高限制,传统的访问控制模型在模型元素粒度和权限动态分配等方面存在的不足,会进一步影响其安全性。针对这一问题,引入时态、环境的概念以及行为模型元素的定义来描述访问活动,提出面向实时备份系统的量化行为访问控制模型QABAC(Quantified Action-Based Access Control）。该模型引入量化属性及信任度的概念,使用量化函数对属性进行动态量化,计算某访问行为的安全度,进一步地根据量化结果,将访问行为分配相应的信任度,并根据信任度配合最终授权策略以决定是否将特定权限授权给该访问行为。实验结果表明,与其他传统访问控制模型相比,QABAC模型具有更灵活及更安全的特点,更适用于当前开放复杂网络环境下数据库的安全保护。     

预算管理信息系统访问控制策略的研究与设计

针对预算管理的特点,讨论了一种在预算管理信息系统中的角色、权限的表示法,并据此给出了一个预算管理信息系统的访问控制策略。将权限分为功能模块访问权限和数据访问权限,将角色分为系统角色和自定义角色,并将功能模块访问权限与系统角色关联,将数据访问权限与自定义角色关联,简化了访问控制机构的实现,提高了访问控制机构的工作效率。     

基于信任度的跨域安全访问控制模型研究*

针对多域环境下基于属性的访问控制模型(ABAC)存在的敏感属性泄露等问题,提出了基于信任度的跨域安全访问控制模型(CD-TBAC)。该模型将属性管理系统与域决策系统结合,对属性进行敏感度划分,并引入基于时间衰减性的动态信任度度量机制。通过判别信任度和敏感度之间的关系决定是否提交敏感属性,并结合实时的信任度与主体的某些属性确定角色,最终根据访问控制策略确定主体权限,实现域内外的安全访问。实验和性能分析表明,该模型在效率上完全接近于ABAC,并具备较高的安全性,能防止敏感属性的泄露、实现匿名访问和抗重放攻击等。     

一种面向PDM系统基于权限位的访问控制方法

访问控制技术是保障信息系统安全的关键技术。在对已有的访问控制技术进行了回顾和分析的基础上,提出了PDM-RBAC访问控制模型。该模型针对PDM系统中存在的用户层次多、数据量大、数据细粒度的控制等因素造成的系统性能低效和管理困难的问题,引入了用户组层次来替代RBAC访问控制模型中的角色层次,并增加了权限层次结构来管理数据权限,同时结合在某企业PDM系统设计和实现中的实践,设计了基于权限位的访问控制算法,用于解决正负权限引起的策略冲突问题。实验结果表明了该模型和算法在大型信息系统权限管理的高效性。     

基于角色的Web服务的授权与访问控制

提出了一个授权与访问控制系统的设计,它以PMI为基本架构,分为授权服务和访问控制两个子系统.权限管理子系统通过各种模块制定全局所需的各种策略,由AA/SOA签发各种策略属性证书;管理员通过注册服务器ARA,为用户分配权限,向AA申请签发用户的属性证书.在访问控制子系统中,策略决策实施点(AEF)截获用户的访问请求及用户身份并发送给访问控制决策点中的ADF,ADF根据权限管理子系统制定好的策略和用户的属性证书计算出用户被授予的访问权限,作出"允许/拒绝"的决策.这样就实现了对Web资源的授权与访问控制,保证了后端Web服务器上共享数据的安全.     

一种面向云存储的动态授权访问控制机制

云存储是一种新型的数据存储体系结构,云存储中数据的安全性、易管理性等也面临着新的挑战.首先,云存储系统需要为用户提供安全可靠的数据访问服务,并确保云端数据的安全性.为此,研究者们针对云存储中数据结构复杂、数据存储量大等特点提出了属性加密(attribute-based encryption,ABE)方案,为云储存系统提供细粒度的密文访问控制机制.在该机制中,数据所有者使用访问策略表示数据的访问权限并对数据进行加密.但数据的访问权限常会因各种原因发生改变,从而导致云中存储密文的频繁更新,进而影响数据的易管理性.为避免访问权限管理造成大量的计算和通信开销,提出了一种高效、安全、易管理的云存储体系结构:利用ABE加密机制实现对密文的访问控制,通过高效的动态授权方法实现访问权限的管理,并提出了不同形式的访问策略之间的转换方法,使得动态授权方法更为通用,不依赖于特定的访问策略形式;针对授权执行者的不同,制定了更新授权、代理授权和临时授权3种动态授权形式,使得动态授权更为灵活、快捷;特别地,在该动态授权方法中,授权执行者根据访问策略的更改计算出最小增量集合,并根据该增量集合更新密文以降低密文更新代价.理论分析和实验结果表明,该动态授权方法能减小资源的耗费、优化系统执行效率、提高访问控制机制灵活性.     

Real-time update of access control policies

Access control policies are security policies that govern access to resources. The need for real-time update of such policies while they are in effect and enforcing the changes immediately, arise in many scenarios. Consider, for example, a military environment responding to an international crisis, such as a war. In such situations, countries change strategies necessitating a change of policies. Moreover, the changes to policies must take place in real-time while the policies are in effect. In this paper we address the problem of real-time update of access control policies in the context of a database system. Access control policies, governing access to the data objects, are specified in the form of policy objects. The data objects and policy objects are accessed and modified through transactions. We consider an environment in which different kinds of transactions execute concurrently some of which may be policy update transactions. We propose algorithms for the concurrent and real-time update of security policies. The algorithms differ on the basis of the concurrency provided and the semantic knowledge used.     

Applying semantic knowledge to real-time update of access control policies

Real-time update of access control policies, that is, updating policies while they are in effect and enforcing the changes immediately, is necessary for many security-critical applications. In this paper, we consider real-time update of access control policies in a database system. Updating policies while they are in effect can lead to potential security problems, such as, access to database objects by unauthorized users. In this paper, we propose several algorithms that not only prevent such security breaches but also ensure the correctness of execution. The algorithms differ from each other in the degree of concurrency provided and the semantic knowledge used. Of the algorithms presented, the most concurrency is achieved when transactions are decomposed into atomic steps. Once transactions are decomposed, the atomicity, consistency, and isolation properties no longer hold. Since the traditional transaction processing model can no longer be used to ensure the correctness of the execution, we use an alternate semantic-based transaction processing model. To ensure correct behavior, our model requires an application to satisfy a set of necessary properties, namely, semantic atomicity, consistent execution, sensitive transaction isolation, and policy-compliant. We show how one can verify an application statically to check for the existence of these properties.     

A lattice-based approach for updating access control policies in real-time

Real-time update of access control policies, that is, updating policies while they are in effect and enforcing the changes immediately and automatically, is necessary for many dynamic environments. Examples of such environments include disaster relief and war zone. In such situations, system resources may need re-configuration or operational modes may change, necessitating a change of policies. For the system to continue functioning, the policies must be changed immediately and the modified policies automatically enforced. In this paper, we propose a solution to this problem—we consider real-time update of access control policies in the context of a database system.     

一种通用访问控制管理模型

目前的访问控制管理模型都是针对某种特定的访问控制模型提出的,不能适应多访问控制模型共存于一个大型系统的情况,一个管理模型不能同时适用于多访问控制模型的主要原因是管理者管理范围定义包含了某种访问控制模型中特有的组件.通过使用各种访问控制模型中共有的主体和权限来定义管理模型中的管理范围,将管理模型与访问控制模型之间的关系抽象为一个用于计算策略相关管理范围的函数,提出了一种能够用来管理不同访问控制模型的通用访问控制管理模型,为了便于模型实际使用,在模型中引入管理空间的概念与实际组织结构相对应,形成分布式访问控制管理结构,同时模型严格区分了管理空间的直接管理者和间接管理者在管理权限上的不同,使得管理者具有一定的自治性.最后讨论了管理模型中的管理规则和语义,证明了模型的完备性,并讨论和分析了针对不同访问控制模型的policy*算法.     

Efficient Policy Analysis for Evolving Administrative Role Based Access Control

Role Based Access Control (RBAC) has been widely used for restricting resource access to only authorized users. Administrative Role Based Access Control (ARBAC) specifies permissions for administrators to change RBAC policies. Due to complex interactions between changes made by different administrators, it is often difficult to comprehend the full effect of ARBAC policies by manual inspection alone. Policy analysis helps administrators detect potential flaws in the policy specification. Prior work on ARBAC policy analysis considers only static ARBAC policies. In practice, ARBAC policies tend to change over time in order to fix design flaws or to cope with the changing requirements of an organization. Changes to ARBAC policies may invalidate security properties that were previously satisfied. In this paper, we present incremental analysis algorithms for evolving ARBAC. Our incremental algorithms determine if a change may affect the analysis result, and if so, use the information of the previous analysis to incrementally update the analysis result. To the best of our knowledge, these are the first known incremental algorithms in literature for ARBAC analysis. Detailed evaluations show that our incremental algorithms outperform the non-incremental algorithm in terms of execution time at a reasonable cost of increased disk space consumption.     

Robot navigation in an unexplored terrain

Navigation planning is one of the most vital aspects of an autonomous mobile robot. Robot navigation for completely known terrain has been solved in many cases. Comparatively less research dealing with robot navigation in unexplored obstacle terrain has been reported in the literature. In recent times this problem has been addressed by adding learning capability to a robot. The robot explores terrain using sensors as it navigates, and builds a terrain model in an incremental manner. In this article we present concurrent algorithms for robot navigation in unexplored terrain. The performance of the concurrent algorithms is analyzed in terms of planning time, travel time, scanning time, and update time. The analysis reveals the need for an efficient data structure to store an obstacle terrain model in order to reduce traversal time, and also to incorporate learning. A modified adjacency list is proposed as a data structure for storing a spatial graph that represents an obstacle terrain. The time complexities of the algorithms that access, maintain, and update the spatial graph are estimated, and the effectiveness of the implementation is illustrated.     

P-RBAC:一种门户环境下的访问控制模型

门户能够有效地实现异构信息之间的集成与协作,并为用户提供可定制、统一且遵循规范的访问服务。然而,由于门户所具有的这些不同于普通Web应用的特性,也使得传统访问控制模型无法在门户中直接使用。提出了一种面向门户系统的访问控制模型P-RBAC。P-RBAC扩展了传统的基于角色访问控制模型,并根据行为状态进一步分为静态模型和动态模型。P-RBAC给出了静态模型和动态模型上的行为规则,提出了具体的动态权限指派和角色组织策略,从而有效地解决了门户的访问控制问题。实际的应用案例证明,P-RBAC模型能够适用于门户的访问控制,并较之传统访问控制模型更高效可行。     

Building access control policy model for privacy preserving and testing policy conflicting problems

This paper proposes a purpose-based access control model in distributed computing environment for privacy preserving policies and mechanisms, and describes algorithms for policy conflicting problems. The mechanism enforces access policy to data containing personally identifiable information. The key component is purpose involved access control models for expressing highly complex privacy-related policies with various features. A policy refers to an access right that a subject can have on an object, based on attribute predicates, obligation actions, and system conditions. Policy conflicting problems may arise when new access policies are generated that are possible to be conflicted to existing policies. As a result of the policy conflicts, private information cannot be well protected. The structure of purpose involved access control policy is studied, and efficient conflict-checking algorithms are developed and implemented. Finally a discussion of our work in comparison with other related work such as EPAL is presented.     

Concurrent Maintenance of Binary Search Trees

The problem of providing efficient concurrent access for independent processes to a dynamic search structure is the topic of this paper. We develop concurrent algorithms for search, update, insert, and delete in a simple variation of binary search trees, called external trees. The algorithm for deletion, which is usually the most difficult operation, is relatively easy in this data structure. The advantages of the data structure and the algorithms are that they are simple, flexible, and efficient, so that they can be used as a part in the design of more complicated concurrent algorithms where maintaining a dynamic search structure is necessary. In order to increase the efficiency of the algorithms we introduce maintenance processes that independently reorganize the data structure and relieve the user processes of nonurgent operations. We also discuss questions of transactions in a dynamic environment and replicated copies of the data structure.