Stabilizing mobile philosophers
We present a self-stabilizing solution to a new version of the dining philosophers problem. We call this problem mobile philosophers problem because the philosophers can move around a logical ring formed out of a dynamic network.

title: Self-Stabilizing Wormhole Routing on Ring Networks
abstract: Wormhole routing is most commonly used in parallel architectures in which messages are sent in small fragments, called flits. It is a lightweight and efficient method of routing messages between parallel processors. Self-stabilization is a technique that guarantees tolerance to transient faults (e.g., memory corruption or communication hazards) for a given protocol. Self-stabilization guarantees that the network recovers to a correct behavior in a finite amount of time, without the need for human intervention. Self-stabilization also guarantees the safety property, meaning that once the network is in a legitimate state, it will remain there until another fault occurs.
This paper presents the first self-stabilizing network algorithm in the wormhole routing model, using the unidirectional ring topology. Our solution benefits from wormhole routing by providing high throughput and low latency, and from self-stabilization by ensuring automatic resilience to all possible transient failures.

title: Anonymous publish/subscribe in P2P networks
abstract: One of the most important issues to deal with in peer-to-peer networks is how to disseminate information. In this paper, we use a completely new approach to solving the information dissemination problem. Our approach uses the publish/subscribe paradigm. The publish/subscribe method is the most inclusive strategy to establish communication between the information providers (publishers) and the information consumers (subscribers). We give a formal definition of publish/subscribe systems. We then use the publish/subscribe communication paradigm to design deterministic protocols (topic and content-based) for peer-to-peer networks. Our protocols are designed on top of an innovative information dissemination scheme, and can cope with the anonymity and mobility of both publishers and subscribers, weak-connectivity, and polarization, which are some of the characteristics of peer-to-peer networks. Moreover, in our solutions, every node could play a role of both publisher and subscriber The algorithms are designed completely independent of the underlying routing substrates. The key advantage of our protocols is that they are scalable without additional re-organization cost. To the best of our knowledge, this is the first time the content-based subscription has been addressed in peer-to-peer networks.

title: Publish/subscribe scheme for mobile networks
abstract: The information dissemination in mobile networks is an important but complex and challenging problem. Designing suitable communication primitives for these systems is critical. One of these primitives is the publish/subscribe paradigm. The publish/subscribe is a strategy to establish communication between the information providers (publishers) and information consumers (subscribers) in a distributed system. Our work focuses on an appropriate distributed infrastructure suitable for a scalable implementation of a publish/subscribe system. We present a formal model which is adapted for the peer-based particular subscription criteria of publish/subscribe systems. Moreover, we propose a general deterministic information diffusion scheme for mobile systems. The three main features of our communication scheme are the following: First, our scheme is well-adapted to scalable systems without compromising any subscription criteria or network reorganization. Second, we maintain the anonymity of the distributed system --- in order to maintain the network structure, we need only local information. Third, our solution is fully decentralized and modular, thus making it appropriate for practical implementations.

title: A derivation system and compositional logic for security protocols
abstract: Many authentication and key exchange protocols are built using an accepted set of standard concepts such as Diffie-Hellman key exchange, nonces to avoid replay, certificates from an accepted authority, and encrypted or signed messages. We propose a general framework for deriving security protocols from simple components, using composition, refinements, and transformations. AS a case study, we examine the structure of a family of key exchange protocols that includes Station-TO-Station (STS), ISO-9798-3, Just Fast Keying (JFK), IKE and related protocols, derving all members of the family from two basic protocols, In order to associate formal proofs with protocol derivations, we extend our previous security protocol logic with preconditions, temporal assertions, composition rules, and Several other improvements. Using the logic, which we prove is sound with respect to the standard symbolic model of protocol execution and attack (the "Dolev-Yao model"), the security properties of the standard signature based Challange- Response protocol and the Diffie-Hellman key exchange protocol are estabilished. The ISO-9798-3 protocol is then proved correct by composing the correctness proofs of these two simple protocols Although our current formal logic is not sufficient to modulary prove security for all of our current protocol derivations. the derivation system provides a framework for further improvements.

title: Secure Protocol Composition
abstract: This paper continues the program initiated in , towards a derivation system for security protocols. The general idea is that complex protocols can be formally derived, starting from basic security components, using a sequence of refinements and transformations, just like logical proofs are derived starting from axioms, using proof rules and transformations. The claim is that in practice, many protocols are already derived in such a way, but informally. Capturing this practice in a suitable formalism turns out to be a considerable task. The present paper proposes rules for composing security protocols from given security components. In general, security protocols are, of course, not compositional: information revealed by one may interfere with the security of the other. However, annotating protocol steps by pre- and post-conditions, allows secure sequential composition. Establishing that protocol components satisfy each other's invariants allows more general forms of composition, ensuring that the individually secure sub-protocols will not interact insecurely in the composite protocol. The applicability of the method is demonstrated on modular derivations of two standard protocols, together with their simple security properties.

title: Compositional analysis of contract-signing protocols
abstract: We develop a general method for proving properties of contract-signing protocols using a specialized protocol logic. The method is applied to the Asokan-Shoup--Waidner and the Garay-Jacobson-MacKenzie protocols. Our method offers certain advantages over previous analysis techniques. First, it is compositional: the security guarantees are proved by combining the independent proofs for the three subprotocols of each protocol. Second, the formal proofs are carried out in a "template" form, which gives us a reusable proof that may he instantiated for the two example protocols, as well as for other protocols with the same arrangement of messages. Third, the proofs follow the design intuition. In particular, in proving game-theoretic properties like fairness, we demonstrate success for the specific strategy that the protocol designer had in mind, instead of non-constructively proving that a strategy exists. Finally, our logical proofs demonstrate security when an unbounded number of sessions are executed in parallel.

title: Computationally sound compositional logic for key exchange protocols
abstract: We develop a compositional method for proving cryptographically sound security properties of key exchange protocols, based on a symbolic logic that is interpreted over conventional runs of a protocol against a probabilistic polynomial-time attacker. Since reasoning about an unbounded number of runs of a protocol involves induction-like arguments about properties preserved by each run, we formulate a specification of secure key exchange that is closed under general composition with steps that use the key We present formal proof rules based on this game-based condition, and prove that the proof rules are sound over a computational semantics. The proof system is used to establish security of a standard protocol in the computational model

title: Generating Boolean networks with a prescribed attractor structure
abstract: Dynamical modeling of gene regulation via network models constitutes a key problem for genomics. The long-run characteristics of a dynamical system are critical and their determination is a primary aspect of system analysis. In the other direction, system synthesis involves constructing a network possessing a given set of properties. This constitutes the inverse problem. Generally, the inverse problem is ill-posed, meaning there will be many networks, or perhaps none, possessing the desired properties. Relative to long-run behavior, we may wish to construct networks possessing a desirable steady-state distribution. This paper addresses the long-run inverse problem pertaining to Boolean networks (BNs).



The long-run behavior of a BN is characterized by its attractors. The rest of the state transition diagram is partitioned into level sets, the j-th level set being composed of all states that transition to one of the attractor states in exactly j transitions. We present two algorithms for the attractor inverse problem. The attractors are specified, and the sizes of the predictor sets and the number of levels are constrained. Algorithm complexity and performance are analyzed. The algorithmic solutions have immediate application. Under the assumption that sampling is from the steady state, a basic criterion for checking the validity of a designed network is that there should be concordance between the attractor states of the model and the data states. This criterion can be used to test a design algorithm: randomly select a set of states to be used as data states; generate a BN possessing the selected states as attractors, perhaps with some added requirements such as constraints on the number of predictors and the level structure; apply the design algorithm; and check the concordance between the attractor states of the designed network and the data states.


AVAILABILITY
The software and supplementary material is available at http://gsp.tamu.edu/Publications/BNs/bn.htm