Gang Yin

A rule-based framework for role-based constrained delegation

In this paper, we concentrate on the delegation problem in trust management (TM) systems. One key point for delegation models is to find the balance between flexibility and controllability. Delegation models in existing TM systems usually have no effective control over delegated privileges or try to enforce too strict constraint on delegation that raises difficulty in policy definition and computational-model constructing. We propose a role-based constrained delegation Model called RCDM04, which is a constrained extension of current role-based trust management systems. RCDM04 comprises a novel delegation framework for multi-centric authorization and proxy-based authentication, proposing to use trusted scope and delegation depth to control the propagation of delegated privileges. This paper also introduces a rule-based language for specifying and enforcing the policies in the model.

An authorization framework based on constrained delegation

In this paper, we distinguish between authorization problems at management level and request level in open decentralized systems, using delegation for flexible and scalable authorization management. The delegation models in existing approaches are limited within one level or only provide basic delegation schemes, and have no effective control over the propagation scope of delegated privileges. We propose REAL, a Role-based Extensible Authorization Language framework for open decentralized systems. REAL covers delegation models at both two levels and provides more flexible and scalable authorization and delegation policies while capable of restricting the propagation scope of delegations. We formally define the semantics of credentials in REAL by presenting a translation algorithm from credentials to Datalog rules (with negation-as-failure). This translation also shows that the semantics can be computed in polynomial time.

Towards more controllable and practical delegation

Delegation is essential to the flexibility and scalability of trust management systems. But unrestricted delegation may result in privilege proliferation and breach the privacy of information systems. The delegation models of existing trust management systems can not avoid privilege transition, and being lack of effective constraints on delegation propagation, which may easily lead to privilege proliferation. In this paper, we propose a generalized constrained delegation model (GCDM), which uses typed privileges to control potential privilege transition, and restricts the propagation scope of delegation trees by a novel delegation constraint mechanism named spacial constraints. This paper also designs a rule-based trust management language named REAL05 to express the policies and semantics for GCDM. REAL05 supports flexible delegation policies while can control the potential privilege proliferation in subsequent delegations. Comprehensive samples and simulation results show that our approach is more controllable and practical.

SRDL: A Simple Role-Based Delegation Logic

With the appearance and growing application of open systems such as Internet, delegation is a primary mechanism to enforce access control in such systems. This paper distinguishes two kinds of delegation: authority delegation (AUD) and access delegation (ACD), and proposes a first-order logic system SRDL to capture the features of the two kinds of delegation models. SRDL properly describes AUD and ACD respectively by using domain-roles and delegating-roles. SRDL provides a flexible approach to control the depth and width of delegation, which is absent in many delegation models such as SRC logic and RT.

RepCom: Towards Reputation Composition over Peer-to-Peer Communities

Peer-To-Peer (P2P) Communities over the Internet contain a large amount of trust evidences that can be used to compute the reputation of peers, but existing reputation systems merely uses the evidences within the scope of one community, neglecting the social charac-teristics of peers’ reputation that can only be actually derived from information based on all communities they participate in. We believe that Internet requires a reputation facility that derives the reputation of peers from evidences over the Internet. In this paper, we propose RepCom, a novel reputation composition ar-chitecture to collect, transform and combine trust evi-dences among P2P communities. RepCom introduces the reputation authority network (RAN) to publish, search and retrieve evidences of peers, and uses a logic-based engine to transform ad hoc evidence data into computable local evidence rules. Finally, RepCom combines the analytic hierarchy process (AHP) and weighted score method (WSM) to compute the final composite reputation of peers that comprehensively reflects their global behavior and certified attributes.

Distributed access control for grid environments using trust management approach

In Grid environments, virtual organizations (VOs) often need to define access control policies to govern who can use which resources for which purpose over multiple policy domains. This is challenging, not only because the entities in VOs must collaborate with each other to share resources across administrative domains, but also because there usually exist a large amount of underlying sites (resource providers) and users in VOs. In this paper, we introduce to use trust management approach to address these problems in Grid environments. We propose a rule-based policy language (RPL) framework to describe the authorization and delegation policies related to VOs, sites and users. This paper also introduces the design of an enhanced community authorization service (ECAS) based on RPL framework, which can be seamlessly integrated with local authorization mechanisms. ECAS uses different kinds of delegation policies for flexible collaboration on authorization between entities in VOs. Compared with similar research works, ECAS enhances the flexibility and scalability of decentralized authorization in Grid environments.

Trust management with safe privilege propagation

Trust management uses delegation to enable decentralized authorization across administrative domains. Delegation passes one’s authority over resources to trusted entities and thus enables more flexible and scalable authorization. However, unrestricted delegation may result in privilege proliferation and breach the privacy of information systems. The delegation models of existing trust management systems do not provide effective control on delegation propagation, and the correctness of constraint enforcement mechanisms is not formally analyzed, which may lead to privilege proliferation. In this paper, we propose a role-based constrained delegation model (RCDM), which restricts the propagation scope of delegation trees by a novel delegation constraint mechanism named spacial constraint. This paper also introduces a rule-based language to specify the policies and the deduction algorithm for constrained delegation defined in RCDM. The soundness and completeness properties of the deduction algorithm ensure the safety and availability of our delegation model.

Towards General Access Control Management for Middleware Security

Middleware security is usually regarded as a wrapper of underlying security mechanisms rather than a infrastructure for enforcement and management of accuss control policies. We argue that there is a need for more generalized security mechanisms at middleware layer to enforce multiple access control policies. We introduce Starch, a novel policy-oriented security architecture at middleware layer, which is distain-gushed from existing middleware security infrastructure-tares mainly in three aspects: (1) Starch can be used to enforce access control policies with finer granularity and different kinds of constraints. (2) Starch provides a more general policy management infrastructure to keep the privacy, consistency and availability of accuss control policies. (3) Starch provides means to clearly separate authorization logic from applications, which will be enforced at middleware layer. Starch is built upon a CORBA middleware and supports mull-tipple access control policies while preserving the mid-dewier designing characteristics.

Towards Role Based Trust Management without Distributed Searching of Credentials

Trust management systems enable decentralized authorization by searching distributed credentials from network. We argue that such distributed searching processes may encounter many technical or non-technical problems, and can be avoided by storing delegation credentials redundantly with acceptable costs. We propose a scoped-role based trust management system ScoRT, using a novel credential affiliation model to compute the credentials necessary for role membership decisions, which can be used to guide the storage, retrieval and revocation of credentials. The algorithm for distributed credential storage and retrieval is designed based on the model and its sound and complete properties are formally analyzed with respect to ScoRT semantics. Complexity analysis and estimation show that, by redundantly storing acceptable amount of delegation credentials, ScoRT enables more practical and automatic authorization without searching credentials from remote entities, and thus helps to overcome the deficiencies of existing approaches.