Heuristic Methods for Security Protocols

Model checking is an automatic verification technique to verify hardware and software systems. However it suffers from state-space explosion problem. In this paper we address this problem in the context of cryptographic protocols by proposing a security property-dependent heuristic. The heuristic weights the state space by exploiting the security formulae; the weights may then be used to explore the state space when searching for attacks

Directed Symbolic Model Checking of Security Protocols

This thesis promotes the use of directed model checking for security protocol verification. In particular, we investigated the possibility of designing heuristics that can reduce the overall size of the state space and can direct the search towards states containing an attack. More precisely, •We have designed three property-specific heuristics namely H1, H2, and H3. The heuristics derive their hints from the security property to be verified and assign weights to states according to their possibility of leading to an attack. • H1 is formally proved correct, i.e., the states pruned by the heuristic H1 do not contain any attack. •An existing tool ASPASyA with conventional model checking algorithm (i.e., depth first search) has been modified so as to integrate our heuristics into it. The resulting tool H -ASPASyA uses an informed search algorithm that is equipped with our heuristics. The heuristics evaluate the states which are then explored in decreasing order of their weights. •The new tool H -ASPASyA is tested against a few protocols to gauge the performance of our heuristics. The results demonstrate the efficiency of our approach. It is worth mentioning that despite being a widely applied verification technique, model checking suffers from the state space explosion problem. Recently directed model checking has been used to mitigate the state space explosion problem in general model checking. However, the directed model checking approaches have not been studied extensively for security protocol verification. This thesis demonstrates the fact that directed model checking can be adapted for security protocol verification in order to yield better results

Topological structure of complex networks and its importance in diffusion

The availability of huge data, due to the tremendous storage capacity of modern computers has allowed the systematic collection, and high processing speed has permitted analysis on that data by researchers on a scale far larger than previously possible. Due to this, complex network formation has been seen and observed in many real and artificial complex systems. As these systems are very large and complex, we cannot get an understanding of these complex systems just by only examining the separate components which constitute these systems. Therefore, modeling the way these components are interconnected in a system is very important for understanding the system as a whole. Further, despite the enormous variation in their components, functions, and sizes, these networks are surprisingly similar in topology, leading to the conjecture that complex systems are governed by the ubiquitous self-organizing principle. In this research, we emphasize on the importance of heterogeneous topological structure of real-world complex networks and its importance in understanding the phenomenon of diffusion in these networks