一个基于视图的数据访问模型

多用户共享一个数据库必然存在一些安全隐患,须加以特定的控制措施以防止非法访问.提出一个基于视图的数据访问模型(VBAC),根据用户名创建与之联系的视图(视图成为该用户访问属于他的数据的惟一窗口),回收所有用户的权限,并将视图的访问权限授予给与之对应的用户,当一个用户登录系统,将他与对应的视图绑定起来,用户的数据访问通过视图间接完成,一旦回收视图的授权,与之对应的用户将不能对数据库进行任何存取.通过授权的数据视图,将用户对数据的操纵限定在特定的行和列,在用户和数据库之间建立信息安全防火墙.在Microsoft SQL Server 2000下测试了该模型的有效性.     

一种基于活动序列的协同设计访问控制模型

为了确保在多用户协同设计环境中对文档及视图访问权限的动态分配与回收、提出了基于活动序列的访问控制模型,采用赋色Petri网描述并实现了模型中活动序列依赖关系约束、角色构造、分配与回收,权限冲突检测等功能。该模型将共享的文档和视图空间按照活动序列划分,把角色分配、回收与活动序列相关联,解决了使用单用户设计软件协同设计中授权用户对访问对象具有持久权限的问题。最后,以协作角色申请过程为例,说明了模型是如何实现访问权限动态分配与回收,以此说明该模型能够适应协同设计中权限随活动变化的访问控制需求。     

访问授权任务依赖关系及其Petri网分析

1 引言访问授权是信息系统安全最重要的措施之一。支持访问授权职责分离原则是评价访问授权模型的重要技术指标。但是,现有的访问授权模型仅支持用户级授权职责分离,即不允许同一用户同时拥有某些访问权限(权限静态互斥),或者不允许同一用户在一次用户访问会话(进程)中激活其所拥有的某些访问权限(权限动态互斥),而对访问授权任务本身存在的互斥关系在目前的相关文献中讨论很少。然而,授权     

基于规则面向用户的动态视图的实现

PostgreSQL是一种对象关系型数据库管理系统.利用PostgreSQL的规则系统,实现了一种面向用户的动态视图建立的方法.该方法利用PostgreSQL的系统表、系统函数,通过创建视图的插入、更新、删除规则,动态的创建会话用户的视图.用户通过访问接口LIBPQ连接到数据库,授权访问和操作自己的视图.在数据库一级对用户数据进行了隔离.     

协作权限动态管理的赋色Petri网模型与验证

针对多用户环境中协作权限动态分配与回收,及可靠性验证问题,提出基于活动、角色的协作权限动态管理机制,采用赋色Petri网建立形式化模型并分析.该模型将共享的协作文档和视图空间按照活动序列划分,角色的分配、回收与活动相关联,解决了传统访问控制中授权用户对访问对象具有持久权限的问题.最后,基于状态空间的分析表明,该模型能够实现活动依赖关系,活动角色绑定可达性及协作权限申请中死锁避免等约束条件的验证,能够满足协同设计中变化频繁的协作权限访问控制需求.     

分级的行列级权限系统的设计和实现

为实现权限系统中用户授权的灵活性和数据级的权限控制,在传统权限访问控制模型的基础上,设计了一种基于内存数据库的分级的行列级权限控制模型。通过分级授权实现授权的灵活性和可继承性,通过分级行列级权限实现数据级权限控制,通过内存数据库和预排序遍历树算法实现数据的快速查询。开发了相应的软件系统,与传统权限模型进行了比较,结果表明了该模型的可行性和高效性。     

基于有限状态机的用户权限隔离模型

针对操作系统中的权限问题,提出了基于有限状态机(FSM)的用户权限隔离模型,将用户的授权访问行为刻画为一个有限状态机,任意用户的有限状态机都只能识别该用户的合法操作序列;同时,模型证明在用户权限交集的部分,即用户访问发生共享的点,容易出现权限窃取或者非法提升等安全问题。最终,利用有限状态机实现了对用户权限隔离的有效识别与判定。     

一种RBAC的改进方案在文件共享系统中的实现

基于高校对文件共享系统“多级共享机制、多级角色权限,并且可以针对特定用户群共享数据”的需求,针对传统RBAC模型进行了简化和改进：即除了RBAC模型的角色授权外,增加了数据对象对于用户的直接授权,使用户所拥有的权限变成用户所属角色的功能权限和用户所获数据对象查看权限之并集。进而,结合“三层架构”分层的思想,采用。 NET及数据库等技术加以实现。在理论层面和实现层面保证了文件共享系统的安全性。     

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。     

扩展RBAC的CRM动态用户访问控制模型与实现

通过研究CRM用户管理系统的特点，提出一种新型的扩展RBAC的CRM动态用户访问控制模型，并对该模型进行详细的定义和分析。该模型通过用户—角色—权限的权限授权模式，减少了授权管理的复杂性；通过角色等级和职责分离约束解决了用户角色职能交叉重叠的问题；引入团队和个性化数据集的概念，改善了系统的数据的访问隔离问题并完善了用户个性化；最后介绍系统实现实例。     

An extended authorization model for relational databases

We propose two extensions to the authorization model for relational databases defined originally by P.G. Griffiths and B. Wade (1976). The first extension concerns a new type of revoke operation, called noncascading revoke operation. The original model contains a single, cascading revoke operation, meaning that when a privilege is revoked from a user, a recursive revocation takes place that deletes all authorizations granted by this user that do not have other supporting authorizations. The new type of revocation avoids the recursive revocation of authorizations. The second extension concerns negative authorization which permits specification of explicit denial for a user to access an object under a particular mode. We also address the management of views and groups with respect to the proposed extensions     

Advanced Authentication Mechanisms for Identity and Access Management in Cloud Computing

Identity management is based on the creation and management of user identities for granting access to the cloud resources based on the user attributes. The cloud identity and access management (IAM) grants the authorization to the end-users to perform different actions on the specified cloud resources. The authorizations in the IAM are grouped into roles instead of granting them directly to the end-users. Due to the multiplicity of cloud locations where data resides and due to the lack of a centralized user authority for granting or denying cloud user requests, there must be several security strategies and models to overcome these issues. Another major concern in IAM services is the excessive or the lack of access level to different users with previously granted authorizations. This paper proposes a comprehensive review of security services and threats. Based on the presented services and threats, advanced frameworks for IAM that provide authentication mechanisms in public and private cloud platforms. A threat model has been applied to validate the proposed authentication frameworks with different security threats. The proposed models proved high efficiency in protecting cloud platforms from insider attacks, single sign-on failure, brute force attacks, denial of service, user privacy threats, and data privacy threats.     

基于TNC的安全接入系统的设计与实现

为了保证网络安全,将威胁隔离在受保护的网络之外,需要在主机接入网络以前对其进行健康状况评估,只允许符合既定安全策略的主机接入网络。针对上述问题,本文基于可信网络连接TNC技术设计并实现了一个安全接入系统,该系统可以根据指定的安全策略,对所有申请接入内网的主机进行身份验证和完整性校验,拒绝不安全的主机接入,最大限度的保证内网安全。     

An authorization-based trust model for multiagent systems

In this paper an authorization-based trust model (ABTM) is described which is designed for managing access to services in a semi-open distributed environment. This is called a multiagent-based smart office environment. In this model, "trust" is defined as a set of authorization attributes that are granted by the owner of a service to the user of the service. Central to this model is a trust manager that redelegates authorizations from the service owner to the requesting user, based on access control policies that are specified by role labels which are assigned to a set of agents. The ABTM scheme is different from a centralized scheme, in which authorizations are granted directly by an authority. It is also different from a fully distributed system,where authorizations are granted based solely on the discretion of the owner of the services. The design philosophy is the separation of trust management and trust application to allow efficient management of access control in large-scale and dynamic environment, such as those that exist in multiagent systems.     

An authorization model for geospatial data

The advent of commercial observation satellites in the new millennium provides unprecedented access to timely information, as they produce images of the Earth with the sharpness and quality previously available only from US, Russian, and French military satellites. Due to the fact that they are commercial in nature, a broad range of government agencies (including international), the news media, businesses, and nongovernmental organizations can gain access to this information. This may have grave implications on national security and personal privacy. Formal policies for prohibiting the release of imagery beyond a certain resolution, and notifying when an image crosses an international boundary or when such a request is made, are beginning to emerge. Access permissions in this environment are determined by both the spatial and temporal attributes of the data, such as location, resolution level, and the time of image download, as well as those of the user credentials. Since existing authorization models are not adequate to provide access control based on spatial and temporal attributes, in this paper, we propose a geospatial data authorization model (GSAM). Unlike the traditional access control models where authorizations are specified using subjects and objects, authorizations in GSAM are specified using credential expressions and object expressions. GSAM supports privilege modes including view, zoom-in, download, overlay, identify, animate, and fly by, among others. We present our access control prototype system that enables subject, object as well as authorization specification via a Web-based interface. When an access request is made, the access control system computes the overlapping region of the authorization and the access request. The zoom-in and zoom-out requests can simply be made through a click of the mouse, and the appropriate authorizations will be evaluated when these access requests are made     

一种虚拟系统视图模型及其应用研究

应用系统集成是软件工程研究领域的热点之一,在目前的研究当中,集成系统的信息安全性引起了人们的关注。为了实现合法的用户在其所授予的权限范围内访问系统信息,本文提出了一种虚拟系统视图模型,该模型使用认证技术以及业务流与数据绑定,在用户终端实现虚拟的系统视图,使其只能操作虚拟系统的功能和数据,从而实现对系统信息的安全保护。     

A Methodology for Structured Database Decomposition

We present a methodology for structured database decomposition based on the relational data model. It is argued that in the distributed database environment, structured database decomposition is attractive both for efficiency and for database security considerations. Techniques for parallel processing and hashed access of structurally decomposed database are presented. Techniques for structured database decomposition to support multiple user views are also described. Structured database decomposition is most advantageous in a query only database environment with stable user views, although dynamic updates can also be handled using techniques described in this paper.     

一种基于指纹特征的远程通行字双向认证方案

提出了一种基于指纹特征并且不泄露指纹特征的远程通行字双向认证方案。在该方案中,根据用户的指纹特征生成通行字,系统服务器中不存储用户指纹模板库,也不存储通行字表,系统管理员无法推导出用户的指纹特征,入侵者不能导出任何用户的通行字和任何保密信息,系统可对来访的用户进行认证,用户也可以对系统的真实性进行认证;该方案能抵御重试攻击,能防止系统内部人员伪造访问记录。     

基于访问控制和中国剩余定理的数据库密钥管理方案的研究

针对密文数据库中数据项加密时会出现数据项密钥量大和安全需求高的问题,通过引入中国剩余定理来管理数据项密钥,提出了一种新的基于访问控制和中国剩余定理的密钥管理方案。当用户申请用户密钥时,密文数据库可以将用户u_i能够访问的大量数据项对应的密钥K_i"合成"用户密钥uki并保存;当用户ui提供用户密钥uk_i和密文查询请求CQR访问密文数据库时,系统会根据系统表和中国剩余定理将用户密钥uk_i再分解成数据项密钥K_i,用户就可以解密数据。该方案不仅实现了对用户访问权限的管理,还解决了大量数据项密钥带来的数据处理时间长、占用系统资源多等问题,提高了密文数据库中密钥管理的效率和安全性。论文最后实现了该密钥管理方案,并对比分析了该方案的安全性。     

Supporting user views

Any emerging standard for object-oriented database systems must include a rich view support mechanism. A user view is a customized window into an application domain. It may be thought of as a simplifying abstraction which hides information that is not accessible to, needed or wanted by a particular user. Because they limit the information available from a given perspective, most views allow read-only access to a database. In this paper it is asserted that by generalizing object identity to include attributes and views - many view updates are made possible. An extended object structure and several categories of view transformation are also presented which allow all user views to be modeled within a single polymorphic database schema.