Optimal self-stabilizing mobile byzantine-tolerant regular register with bounded timestamps

This paper proposes the first implementation of a self-stabilizing regular register emulated by n servers that is tolerant to both Mobile Byzantine Agents and transient failures in a round-free synchronous model. Differently from existing Mobile Byzantine Tolerant register implementations, this paper considers a weaker model where: (i) the computation of the servers is decoupled from the movements of the Byzantine agents, i.e., movements may happen before, concurrently, or after the generation or the delivery of a message, and (ii) servers are not aware of their failure state i.e., they do not know if and when they have been corrupted by a Mobile Byzantine agent. The proposed protocol tolerates (i) any finite number of transient failures, and (ii) up to f Mobile Byzantine agents. In addition, our implementation uses bounded timestamps from the Z13 domain and it is optimal with respect to the number of servers needed to tolerate f Mobile Byzantine agents in the given model (i.e., n>6f when Δ=2δ, and n>8f when Δ=δ, where Δ represents the period at which the Byzantine agents move and δ is the upper bound on the communication latency)

Self-stabilization in self-organized Multihop Wireless Networks

In large scale multihop wireless networks, flat architectures are not scalable. In order to overcome this major drawback, clusterization is introduced to support self-organization and to enable hierarchical routing. When dealing with multihop wireless networks the robustness is a main issue due to the dynamicity of such networks. Several algorithms have been designed for the clusterization process. As far as we know, very few studies check the robustness feature of their clusterization protocols. Moreover, when it is the case, the evaluation is driven by simulations and never by a theoretical approach. In this paper, we show that a clusterization algorithm, that seems to present good properties of robustness, is self-stabilizing. We propose several enhancements to reduce the stabilization time and to improve stability. The use of a Directed Acyclic Graph ensures that the self-stabilizing properties always hold regardless of the underlying topology. These extra criterion are tested by simulations

Brief announcement: Optimal self-stabilizing mobile byzantine-tolerant regular register with bounded timestamps

This paper investigates on the implementation of a self-stabilizing regular register emulated by n servers that is tolerant to both mobile Byzantine agents, and transient failures in a round-free synchronous model. Differently from existing Mobile Byzantine tolerant register implementation, this paper considers a more powerful adversary where (i) the message delay (i.e., δ) and the period of mobile Byzantine agents movement (i.e., Δ) are completely decoupled and (ii) servers are not aware of their state i.e., they do not know if they have been corrupted or not by a mobile Byzantine agent. We claim the existence of an optimal protocol that tolerates (i) any number of transient failures, and (ii) up to f Mobile Byzantine agents

A Self-Stabilizing Link-Coloring Protocol Resilient to Unbounded Byzantine Faults in Arbitrary Networks 1

Self-stabilizing protocols can tolerate any type and any number of transient faults. However, in general, self-stabilizing protocols provide no guarantee about their behavior against permanent faults. This paper proposes a self-stabilizing link-coloring protocol resilient to (permanent) Byzantine faults in arbitrary networks. The protocol assumes the central daemon, and uses 2 ∆ − 1 colors where ∆ is the maximum degree in the network. This protocol guarantees that any link (u, v) between nonfaulty processes u and v is assigned a color within 2 ∆ + 2 rounds and its color remains unchanged thereafter. Thus, our protocol achieves Byzantine-fault tolerance with containment radius of one, which is trivially optimal

Parameterized verification of algorithms for oblivious robots on a ring

We study verification problems for autonomous swarms of mobile robots that self-organize and cooperate to solve global objectives. In particular, we focus in this paper on the model proposed by Suzuki and Yamashita of anonymous robots evolving in a discrete space with a finite number of locations (here, a ring). A large number of algorithms have been proposed working for rings whose size is not a priori fixed and can be hence considered as a parameter. Handmade correctness proofs of these algorithms have been shown to be error-prone, and recent attention had been given to the application of formal methods to automatically prove those. Our work is the first to study the verification problem of such algorithms in the parameterized case. We show that safety and reachability problems are undecidable for robots evolving asynchronously. On the positive side, we show that safety properties are decidable in the synchronous case, as well as in the asynchronous case for a particular class of algorithms. Several properties on the protocol can be decided as well. Decision procedures rely on an encoding in Presburger arithmetics formulae that can be verified by an SMT-solver. Feasibility of our approach is demonstrated by the encoding of several case studies

Evaluating a data removal strategy for grid environments using colored Petri nets

We use Colored Petri Nets (CPNs) for the modeling and performance analysis of grid architectures. We define a strategy for the optimization of grid storage usage, based on the addition of data removal tasks to grid workflows. We evaluate the strategy by simulating our CPN model of the grid. Experiments show that the strategy significantly reduces the amount of storage space needed to execute a grid application