Comparing BDD and SAT based techniques for model checking Chaum's Dining Cryptographers Protocol

We analyse different versions of the Dining Cryptographers protocol by means of automatic verification via model checking. Specifically we model the protocol in terms of a network of communicating automata and verify that the protocol meets the anonymity requirements specified. Two different model checking techniques (ordered binary decision diagrams and SAT-based bounded model checking) are evaluated and compared to verify the protocols

TAPAs: A Tool for the Analysis of Process Algebras

Process algebras are formalisms for modelling concurrent systems that permit mathematical reasoning with respect to a set of desired properties. TAPAs is a tool that can be used to support the use of process algebras to specify and analyze concurrent systems. It does not aim at guaranteeing high performances, but has been developed as a support to teaching. Systems are described as process algebras terms that are then mapped to labelled transition systems (LTSs). Properties are verified either by checking equivalence of concrete and abstract systems descriptions, or by model checking temporal formulae over the obtained LTS. A key feature of TAPAs, that makes it particularly suitable for teaching, is that it maintains a consistent double representation of each system both as a term and as a graph. Another useful didactical feature is the exhibition of counterexamples in case equivalences are not verified or the proposed formulae are not satisfied

Process Algebras

Process Algebras are mathematically rigorous languages with well defined semantics that permit describing and verifying properties of concurrent communicating systems. They can be seen as models of processes, regarded as agents that act and interact continuously with other similar agents and with their common environment. The agents may be real-world objects (even people), or they may be artifacts, embodied perhaps in computer hardware or software systems. Many different approaches (operational, denotational, algebraic) are taken for describing the meaning of processes. However, the operational approach is the reference one. By relying on the so called Structural Operational Semantics (SOS), labelled transition systems are built and composed by using the different operators of the many different process algebras. Behavioral equivalences are used to abstract from unwanted details and identify those systems that react similarly to external experiments

Using formal methods to support testing

Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing

An Abstract Formal Basis for Digital Crowds

Crowdsourcing, together with its related approaches, has become very popular in recent years. All crowdsourcing processes involve the participation of a digital crowd, a large number of people that access a single Internet platform or shared service. In this paper we explore the possibility of applying formal methods, typically used for the verification of software and hardware systems, in analysing the behaviour of a digital crowd. More precisely, we provide a formal description language for specifying digital crowds. We represent digital crowds in which the agents do not directly communicate with each other. We further show how this specification can provide the basis for sophisticated formal methods, in particular formal verification.Comment: 32 pages, 4 figure

Automatic Verification of Communicative Commitments using Reduction

In spite of the fact that modeling and verification of the Multi-Agent Systems (MASs) have been since long under study, there are several related challenges that should still be addressed. In effect, several frameworks have been established for modeling and verifying the MASs with regard to communicative commitments. A bulky volume of research has been conducted for defining semantics of these systems. Though, formal verification of these systems is still unresolved research problem. Within this context, this paper presents the CTLcom that reforms the CTLC, i.e., the temporal logic of the commitments, so as to enable reasoning about the commitments and fulfillment.  Moreover, the paper introduces a fully-automated method for verification of the logic by means of trimming down the problem of a model that checks the CTLcom to a problem of a model that checks the GCTL*, which is a generalized version of the CTL* with action formulae. By so doing, we take advantage of the CWB-NC automata-based model checker as a tool for verification. Lastly, this paper presents a case study drawn from the business field, that is, the NetBill protocol, illustrates its implementation, and discusses the associated experimental results in order to illustrate the efficiency and effectiveness of the suggested technique.   Keywords: Multi-Agent Systems, Model Checking, Communicative commitment's, Reduction