The popularity of online social networks (OSNs) makes the protection of users' private information an important but scientifically challenging problem. In the literature, relationship-based access control schemes have been proposed to address this problem. However, with the dynamic developments of OSNs, we identify new access control requirements which cannot be fully captured by the current schemes. In this paper, we focus on public information in OSNs and treat it as a new dimension which users can use to regulate access to their resources. We define a new OSN model containing users and their relationships as well as public information. Based on this model, we introduce a variant of hybrid logic for formulating access control policies. We exploit a type of category information and relationship hierarchy to further extend our logic for its usage in practice. In the end, we propose a few solutions to address the problem of information reliability in OSNs, and formally model collaborative access control in our access control scheme.
proposed the first relationship-based access control model in @cite_4 , where the relationships between the qualified requester and the owner are interpreted into three aspects, i.e., relationship type, depth and trust level. @cite_29 , the authors used semantic web technology including OWL and SWRL to extend the model of @cite_4 . They also proposed administrative and filtering policies which can be used for collaborative and supervising access control, respectively.
@cite_29 @cite_4
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User-to-user (U2U) relationship-based access control has become the most prevalent approach for modeling access control in online social networks (OSNs), where authorization is typically made by tracking the existence of a U2U relationship of particular type and or depth between the accessing user and the resource owner. However, today's OSN applications allow various user activities that cannot be controlled by using U2U relationships alone. In this paper, we develop a relationship-based access control model for OSNs that incorporates not only U2U relationships but also user-to-resource (U2R) and resource-to-resource (R2R) relationships. Furthermore, while most access control proposals for OSNs only focus on controlling users' normal usage activities, our model also captures controls on users' administrative activities. Authorization policies are defined in terms of patterns of relationship paths on social graph and the hop count limits of these path. The proposed policy specification language features hop count skipping of resource-related relationships, allowing more flexibility and expressive power. We also provide simple specifications of conflict resolution policies to resolve possible conflicts among authorization policies. Access control policy is typically defined in terms of attributes, but in many applications it is more natural to define permissions in terms of relationships that resources, systems, and contexts may enjoy. The paradigm of relationship-based access control has been proposed to address this issue, and modal logic has been used as a technical foundation. We argue here that hybrid logic -- a natural and well-established extension of modal logic -- addresses limitations in the ability of modal logic to express certain relationships. We identify a fragment of hybrid logic to be used for expressing relationship-based access-control policies, show that this fragment supports important policy idioms, and demonstrate that it removes an exponential penalty in existing attempts of specifying complex relationships such as "at least three friends". We also capture the previously studied notion of relational policies in a static type system. The Relationship-Based Access Control (ReBAC) model was recently proposed as a general-purpose access control model. It supports the natural expression of parameterized roles, the composition of policies, and the delegation of trust. Fong proposed a policy language that is based on Modal Logic for expressing and composing ReBAC policies. A natural question is whether such a language is representationally complete, that is, whether the language is capable of expressing all ReBAC policies that one is interested in expressing. In this work, we argue that the extensive use of what we call Relational Policies is what distinguishes ReBAC from traditional access control models. We show that Fong's policy language is representationally incomplete in that certain previously studied Relational Policies are not expressible in the language. We introduce two extensions to the policy language of Fong, and prove that the extended policy language is representationally complete with respect to a well-defined subclass of Relational Policies. Social Network Systems pioneer a paradigm of access control that is distinct from traditional approaches to access control. Gates coined the term Relationship-Based Access Control (ReBAC) to refer to this paradigm. ReBAC is characterized by the explicit tracking of interpersonal relationships between users, and the expression of access control policies in terms of these relationships. This work explores what it takes to widen the applicability of ReBAC to application domains other than social computing. To this end, we formulate an archetypical ReBAC model to capture the essence of the paradigm, that is, authorization decisions are based on the relationship between the resource owner and the resource accessor in a social network maintained by the protection system. A novelty of the model is that it captures the contextual nature of relationships. We devise a policy language, based on modal logic, for composing access control policies that support delegation of trust. We use a case study in the domain of Electronic Health Records to demonstrate the utility of our model and its policy language. This work provides initial evidence to the feasibility and utility of ReBAC as a general-purpose paradigm of access control.