Content Access Control Research Articles

ACTkit: A Framework for the Definition and Enforcement of Role, Content and Context-based Access Control Policies

This work describes a framework, called ACTkit, for the definition and enforcement of dynamic access control policies on (multi-tiered) information systems. ACTkit embodies a language for defining security policies built out of role-, context- and content-based access control rules and an access control module responsible for the policy enforcement. A model, which has been defined as an extension of Hierarchical RBAC to provide a precise semantics for the security policies, is also presented and discussed.

An efficient key management scheme for content access control for linear hierarchies

The content access control problem appears in any context with a set of users and resources. The difference in access rights of the users defines classes, where members of a given class have exactly the same access rights. A hierarchy can be defined on the classes. Linear hierarchies constitute a particularly interesting type of hierarchies. They appear in a wide range of applications such as secure multi-layered data streaming and communications within security corps. Many proposals have dealt with key management issues for tree hierarchies but they result in unjustified overhead when applied to linear hierarchies.In this paper, we discuss the general problem of Content Access Control in a Hierarchy (CACH). Thereafter, we present the main requirements in key management to ensure confidentiality in linear hierarchies. In particular, we define a model to make a uniform and coherent description of the existing key management schemes. Thereafter, we propose an efficient key management scheme for linear hierarchies that not only provides mechanisms to manage membership changes but also hierarchy shape changes, and we describe it using our model. We conduct intensive simulations which show that our solution scales very well in terms of storage, bandwidth, and computation. Finally, we determine the complexity of some well-known key management schemes and compare them to the complexity of our scheme. This comparison shows that our scheme offers efficient compromises in complexity and overall overheads.

A query verification scheme for dynamic outsourced databases

Recently, Kyriakos et al. proposed a Partially Materialized Digest scheme ( PMD ). Their scheme uses separate indexes for the data and the verification information to realize the authenticity and completeness verification in outsourced database. In this paper, we analyze PMD and show the drawbacks in PMD such as the slow update, the collusion and forgery attacks, and no content access control etc. In order to overcome these defects, the idea of designated verifier signature is introduced into query verification, and a secure, efficient query verification scheme for dynamic outsourced databases is proposed based on PMD . The analysis of security and performance shows that the proposed scheme has not only the same advantages with PMD , but also prevents the collusion and forgery attacks as well as enforces content access control. Furthermore, the update speed of the proposed scheme is faster than PMD , the storage cast of the proposed is lower than PMD .

Multiple Level Access Control Method for Hierarchical Multimedia Content Using Low-complexity Key Generating Schemes

We propose an efficient method of access control for hierarchical multimedia content. The proposed method simultaneously controls access to each medium contained in multimedia content and to each entity which is hierarchically organized in an individual medium. Even though this method achieves such fine control, it does not increase the computational complexity for key derivation. In our method, a service provider manages only a single key to control access to one multimedia content regardless of the number of media and the depth of hierarchy in each medium. The single managed key is not delivered to any user.

Flexible-Pay-Per-Channel: A New Model for Content Access Control in Pay-TV Broadcasting Systems

In the past, two models, pay-per-channel (PPC) and pay-per-view (PPV), for content access control in pay-TV broadcasting systems have been proposed. In PPC, a subscriber subscribes to one or multiple group(s) of channels, prearranged by the service provider, for a fixed period of time. Thus, it is unfair for the subscriber because the subscriber can not subscribe an arbitrary combination of channels according to his/her preference, and can not dynamically unsubscribe/change his/her subscription during the subscription period. On the other hand, PPV specifies that a subscriber can pay for each single program; thus, it provides a fair service. However, compared with PPC, PPV makes the subscriber inconvenient because of the high subscription frequency and low flexibility of channel selection. Moreover, all the existing PPV systems are only suitable for a small-scale Pay-TV system with limited users because of the overhead for transmission and storage. In this paper, we define a new model, flexible-PPC (F-PPC), which combines the properties and the advantages of PPC and PPV. F-PPC is an improved model of PPC for its fairness. It allows a subscriber to subscribe freely to his/her favorite channels, and unsubscribe/change his/her subscription at any time. Furthermore, it eliminates the inconvenience in PPV, and is suitable for a large-scale Pay-TV system with numerous subscribers and channels. In order to fulfill the requirements of F-PPC, we propose a new conditional access system (CAS) with a four-level key hierarchy. The proposed CAS utilizes a structure of a binary tree to update keys rapidly; therefore, the service provider can promptly update necessary keys when the subscribers change their subscriptions or leave the system. Compared with the existing CAS systems, our CAS is more efficient and flexible to support F-PPC.

AACS-compatible multimedia joint encryption and fingerprinting: Security issues and some solutions

In this paper, a new multimedia joint encryption and fingerprinting (JEF) scheme embedded into the advanced access content system (AACS) is proposed for multimedia transmission over networks. AACS is selected because it has been jointly developed by many famous companies and has been considered as the leading technology in content access control and multimedia distribution. In this framework, many attack points exist and can be exploited to defeat it. Furthermore, multiple attack points can be combined to form multi-point collusion attacks, which also endanger the proposed system. In this paper, we address the security concerns toward AACS-compatible JEF system in its entirety and propose solutions to cope with some security threats. The contributions of this paper include: (i) applying multimedia encryption at different points to resist some attacks points; (ii) proposing rewritable fingerprint embedding (RFE) to deal with some multi-point collusion attacks; (iii) designing a perceptual security spectrum metric (PSSM) to evaluate the degree of security when multiple encryptions are applied. The feasibility of the proposed AACS-compatible JEF method is further demonstrated through simulation results.

Secure content access and replication in pure P2P networks

Despite the advantages offered by pure Peer-to-Peer (P2P) networks (e.g. robustness and fault tolerance), a crucial requirement is to guarantee basic security properties, such as content authenticity and integrity, as well as to enforce appropriate access control policies. These mechanisms would pave the way for new models in which content providers can exert some control over the replication and file sharing process. However, the extremely decentralized nature of these environments makes impossible to apply classic solutions that rely on some kind of fixed infrastructure, typically in the form of on-line trusted third parties (TTP). In this paper, we introduce a suite of protocols for content authentication and access control in pure P2P networks based on attribute certificates that does not rely on the existence of a public key infrastructure (PKI), privilege management infrastructure (PMI), or any other form of centralized authority. We provide an analysis concerning the efficiency (computational effort and communication overhead) and the security of our proposal.

Key management for content access control in a hierarchy

The need for content access control in hierarchies (CACH) appears naturally in all contexts where a set of users have different access rights to a set of resources. The hierarchy is defined using the access rights. The different resources are encrypted using different keys. Key management is a critical issue for scalable content access control. In this paper, we study the problem of key management for CACH. We present main existing access control models, and show why these models are not suitable to the CACH applications, and why they are not implemented in the existing key management schemes. Furthermore, we classify these key management schemes into two approaches, and construct an access control model for each approach. The proposed access control models are then used to describe the schemes in a uniform and coherent way. A final contribution of our work consists of a classification of the CACH applications, a comparison of the key management schemes, and a study of the suitability of the existing schemes to the CACH applications with respect to some analytical measurements.

Content-triggered trust negotiation

The focus of access control in client/server environments is on protecting sensitive server resources by determining whether or not a client is authorized to access those resources. The set of resources is usually static, and an access control policy associated with each resource specifies who is authorized to access the resource. In this article, we turn the traditional client/server access control model on its head and address how to protect the sensitive content that clients disclose to and receive from servers. Since client content is often dynamically generated at run-time, the usual approach of associating a policy with the resource (content) a priori does not work. We propose a general-purpose access control model designed to detect whenever sensitive information is being transmitted, and determine whether the sender or receiver is authorized. The model identifies sensitive content, maps the sensitive content to an access control policy, and establishes the trustworthiness of the sender or receiver before the sensitive content is disclosed or received. We have implemented the model within TrustBuilder, an architecture for negotiating trust between strangers based on properties other than identity. The implementation targets open systems, where clients and servers do not have preexisting trust relationships. The implementation is the first example of content-triggered trust negotiation. It currently supports access control for sensitive content disclosed by web and email clients.

サーバ型放送におけるコンテンツのアクセス制御方式

This paper presents an RMP (Rights Management and Protection) system for Digital Broadcasting Based on Home Servers to be used with receivers and home storage devices. We clarified the requirements required for rights protection of contents in Digital Broadcasting Based on Home Servers, and developed an RMP system that meets those requirements. This RMP system enables rights protection and advanced access control (term of validity, usage and charge condition, etc.) of content stored on home storage devices. We have also proposed a method for multiplexing scramble keys synchronous with MPEG-2 TS video packets, to achieve a non-linear playback function of contents encrypted by the developed RMP system. We confirmed that non-linear playback and trick-play function of contents encrypted by the developed RMP system can be processed in real time.