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 multilevel secure (MLS) 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 two-phase locking high priority (2PLHP) algorithm is based on a two-phase locking protocol and the Secure optimistic concurrency control (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. (C) 2002 Elsevier Science Inc. All rights reserved.