Protected pointers to specify access privileges in distributed systems

With reference to a distributed environment consisting of nodes connected in an arbitrary network topology, we propose the organization of a protection system in which a set of subjects, e.g. processes, generates access attempts to memory segments. One or more primary passwords are associated with each node. An access to a given segment can be accomplished successfully only if the subject attempting the access holds an access privilege, certified by possession of a valid protected pointer (p-pointer) referencing that segment. Each p-pointer includes a local password; the p-pointer is valid if the local password descends from a primary password by application of a universally known, parametric one-way generation function. A set of protection primitives makes it possible to manage the primary passwords, to reduce p-pointers to include less access rights, to allocate new segments, to delete existing segments, to read the segment contents and to overwrite these contents. The resulting protection environment is evaluated from a number of viewpoints, which include p-pointer forging and revocation, the network traffic generated by the execution of the protection primitives, the memory requirements for p-pointer storage, security, and the relation of our work to previous work. An indication of the flexibility of the p-pointer concept is given by applying p-pointers to the solution of a variety of protection problems

Access control scheme for partially ordered set hierarchy with provable security

In many multi-user information systems, the users are organized as a hierarchy. Each user is a subordinate, superior and/or coordinate of some others. In such systems, a user has access to the information if and only if the information belongs to the user or his/her subordinates. Hierarchical access control schemes are designed to enforce such access policy. In the past years, hierarchical access control schemes based on cryptography are intensively researched. Much progress has been made in improving the schemes’ performance and security. The main contribution of this thesis is a new hierarchical access control scheme. This is the first one that provides strict security proof under a comprehensive security model that covers all possible cryptographic attacks to a hierarchical access control scheme. The scheme is designed and analyzed based on the modern cryptography approach, i.e., defining the security model, constructing the scheme based on cryptography primitives, and proving the security of the scheme by reducing the cryptography primitives to the scheme. Besides the security property, this scheme also achieves good performance in consuming small storage space, supporting arbitrary and dynamic hierarchial structures. In the thesis, we also introduce the background in cryptography and review the previous schemes

Interaction and interest management in a scripting language.

Interaction management is concerned with the protocols that govern interactive activities among multiple users or agents in networked collaborative environments. Interest management is concerned with the relevance-based data filtering in networked collaborative environments. The main objective of the former is to structure interactive activities according to the requirements of the application concerned, while the main objective of the latter is to provide secured data transmission of a subset of information relevant to each recipient. The research in these two important aspects of networked software has largely been carried out in specific application domains such as online meetings, online groupware and online games. This thesis is concerned with the design and implementation of high-level language constructs for interaction and interest management. The work that has been undertaken includes: an abstract study of interactive activities and data transmission in networked collaborative environments through a large number of variations of the noughts and crosses game; the design of a set of language constructs for specifying a variety of interaction protocols; the design of a set of language constructs for specifying secured data sharing with relevance-based filtering; the implementation of these language constructs in the form of a major extension of a scripting language JACIE (Java-based Authoring Language for Collaborative Interactive Environments); the development of two demonstration applications, namely e-leaming on Simulation of Network Trouble Shooting and online Bridge, using the extended JACIE for demonstrating the technical feasibility and usefulness of the design. These high-level language constructs support a class of complicated software features in networked collaborative applications, such as turn management, interaction timing, group formation, dynamic protocol changes, distributed data sharing, access control, authentication and information filtering. They enable programmers to implement such features in an intuitive manner without involving low-level system programming directly, which would otherwise require the knowledge and skills of experienced network programmers