Cryptographic Access Control for a Network File System

Abstract

The rapid growth of mobile computing and the deployment of large distributed systems which span multiple administrative domains has created new challenges for security systems. Changing usage patterns and the physical limitations of mobile devices require users to rely on services provided by remote elements in the system to facilitate data access and storage requirements. Users need to minimize the trust placed in remote elements of the system such as the transmission mechanism and file server which may be beyond their control. They require secure mechanisms for accessing the sharing protected data. The access control mechanism deployed on the remote server should be flexible but capable of providing the levels of security required. Finally access control should not constitute a bottleneck in the system.

This thesis will investigate the feasibility of using cryptography as a form of access control in distributed systems. Cryptographic Access Control is a new paradigm in access control mechanisms which uses a combination of symmetric and asymmetric cryptography to provide user authentication, data confidentiality and integrity in distributed file systems. Its design reflects the challenges placed on systems by the changing operational environment. It is flexible enough to operate across multiple domains with varying security requirements and offers a high degree of resource protection in untrusted enviornments. It makes no assumptions about the security of remote elements in the system such as the transport mechanism or file server and only requires that the user place complete trust in his own machine. Access control is essentially determined by the possesion of cryptography keys. Possession of the public key allows a users to have read access to data and possession of the private key allows a user to have write access to data.