Maintaining security and timeliness in real-time database system

Real-time database systems can have security constraints in addition to timing constraints. Such real-time systems are typically contained in environments that exhibit hierarchical propagation of information, where mandatory access control for security is required. Conventional multi-level secure database models that implement mandatory access control are inadequate for time-critical applications and conventional real-time database models do not address security constraints. The objective of this work is to incorporate security constraints in real-time database systems in such a way that not only is security achieved, but achieving security does not degrade real-time performance significantly in terms of deadlines missed. We present two concurrency control algorithms for secure real-time databases: the Secure 2PLHP algorithm is based on a two-phase locking protocol and the Secure OPT algorithm uses the properties of an optimistic concurrency protocol. We implement the two algorithms and study their performance using a real-time database system simulation model. Our study covers both soft and firm real-time databases. Results show that both the algorithms perform fairly well in terms of security and timeliness compared to non-secure algorithms. We show that achieving increased security does not necessarily mean an increased sacrifice in real-time performance. Submitted to the Journal of Systems and Software