Journal of Computer Security

Intrusion detection systems' (IDS) effectiveness requires balancing characteristics and elements so they fit together in appropriate compromises to create good network security systems. One major gauge for IDS effectiveness is the ability to detect attacks within operational specifications. Gigabit IDS sensors as opposed to Megabit IDS sensors promise dramatic increase in component performance and functional opportunities, possibly leading to dramatically changed system balance and overall performance. The research described here examines the system benefits of using a single Gigabit IDS sensor instead of multiple Megabit sensors for a wide range of defined system attacks, network traffic characteristics, and for their contexts of operational concepts and deployment techniques. The experimental results are analyzed in the context of practical experiences in the operation of these IDS systems. The difference in architectural designs, deployment strategies and operational concepts that characterized their performance in exploiting the strengths of attack systems are discussed.

We introduce a simple Role-based Trust-management language RT 0 and a set-theoretic semantics for it. We also introduce credential graphs as a searchable representation of credentials in RT 0 and prove that reachability in credential graphs is sound and complete with respect to the semantics of RT 0 . Based on credential graphs, we give goal-directed algorithms to do credential chain discovery in RT 0 , both when credential storage is centralized and when credential storage is distributed. A goal-directed algorithm begins with an access-control query and searches for credentials relevant to the query, while avoiding considering the potentially very large number of credentials that are unrelated to the access-control decision at hand. This approach provides better expected-case performance than bottom-up algorithms. We show how our algorithms can be applied to SDSI 2.0 (the ‘SDSI’ part of SPKI/SDSI 2.0).

Our goal-directed, distributed chain discovery algorithm finds and retrieves credentials as needed. We prove that the algorithm is correct by proving that the algorithm is sound and complete with respect to the credential graph composed of the credentials it retrieves, and that the algorithm retrieves all credentials that constitute a traversable chain. We further introduce a storage type system for RT 0 , which guarantees traversability of chains when credentials are well typed. This type system can also help improve search efficiency by guiding search in the right direction, making distributed chain discovery with large number of credentials feasible.

An existing approach based on induction and theorem proving is tailored to the verification of security protocols that make use of smart cards. Smart cards are modelled operationally, hence only their functionalities, rather than their implementative technicalities, are of interest. The spy can steal certain smart cards, and clone others while learning their stored secrets. In terms of generality, the approach scales up to protocols that assume secure or insecure means between agents and smart cards, as well as to smart cards being PIN-operated or PIN-less. In terms of extensibility, new, application-dependent smart card functionalities can be easily included.

The approach is demonstrated on the key distribution protocol designed by Shoup and Rubin [30], and the assumptions are studied that are necessary on the smart cards for the protocol goals to be met. It is found that, if the data buses of the smart cards are unreliable as to produce outputs in an unspecified order, then the protocol does not confirm to the peers its goals of confidentiality, authentication, and key distribution because of lack of explicitness. A simple fix is introduced and proved.