Study for Automatically Analysing Non-repudiation

While security issues such as secrecy and authentication have been studied intensively, most interest in non-repudiation protocols has only come in recent years. Non-repudiation services must ensure that when two parties exchange informations over a network, neither one nor the other can deny having participated in this communication. Consequently a non-repudiation protocol has to generate evidences of participation to be used in the case of a dispute. In this paper, we present a description of non-repudiation services, and illustrate them on the Fair Zhou-Gollmann protocol. Then we show how to define non-repudiation properties with the AVISPA tool and explain how they can be automatically verified

Automatic Methods for Analyzing Non-Repudiation Protocols with an Active Intruder

Non-repudiation protocols have an important role in many areas where secured transactions with proofs of participation are necessary. Formal methods are clever and without error, therefore using them for verifying such protocols is crucial. In this purpose, we show how to partially represent non-repudiation as a combination of authentications on the Fair Zhou-Gollmann protocol. After discussing its limits, we define a new method based on the handling of the knowledge of protocol participants. This method is very general and is of natural use, as it consists in adding simple annotations, like for authentication problems. The method is very easy to implement in tools able to handle participants knowledge. We have implemented it in the AVISPA Tool and analyzed the optimistic Cederquist-Corin- Dashti protocol, discovering two unknown attacks. This extension of the AVISPA Tool for handling non-repudiation opens a highway to the specification of many other properties, without any more change in the tool itself

Proceedings of the 19th International Workshop on Unification

Proceedings of the 19th international workshop on Unification, held during RDP'2005 in Nara, Japan, on April 22, 2005.UNIF is the main international meeting on unification. Unification is concerned with the problem of identifying given terms, either syntactically or modulo a given logical theory. Syntactic unification is the basic operation of most automated reasoning systems, and unification modulo theories can be used, for instance, to build in special equational theories into theorem provers

A Constraint-based Approach to Web Services Provisioning

In this paper we consider the provisioning problem of Web services. Our framework is based on the existence of an abstract composition, i.e., the way some services of different types can be combined together in order to achieve a given task. Our approach consists in instantiating this abstract representation of a composite Web service by selecting the most appropriate concrete Web services. This instantiation is based on constraint programming techniques which allows us to match the Web services according to a given request. Our proposal performs this instantiation in a distributed manner, i.e., the solvers for each service type are solving some constraints at one level, and they are forwarding the rest of the request (modified by the local solution) to the next services. When a service cannot provision part of the composition, a distributed backtrack mechanism enables to change previous solutions (i.e., provisions). A major interest of our approach is to preserve privacy: solutions are not sent to the whole composition, services know only the services to which they are connected, and parts of the request that are already solved are removed from the next requests. We introduce a specific data structure, namely Message Treatment Structure, for modeling the problem. We show the interest of this data structure to express the general principles of our framework and the related algorithms

Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes

In this paper the design, fabrication and characterization of a bioinspired overlayer deposited on a GaN LED is described. The purpose of this overlayer is to improve light extraction into air from the diode's high refractive-index active material. The layer design is inspired by the microstructure found in the firefly Photuris sp. The actual dimensions and material composition have been optimized to take into account the high refractive index of the GaN diode stack. This two-dimensional pattern contrasts other designs by its unusual profile, its larger dimensions and the fact that it can be tailored to an existing diode design rather than requiring a complete redesign of the diode geometry. The gain of light extraction reaches values up to 55% with respect to the reference unprocessed LED.Comment: 9 pages, 9 Figures, published in Optics Expres

Rough Sets based Proofs Visualisation

Colloque sur invitation.We present here an approach we used for proving important properties of clopen topological spaces. We combine powerful theorem provers techniques (and implementations) with a graphical technique based on a graphical representation of a rough set, called Rough Diagrams. Rough Diagrams are a generalization of a classical notion of Venn Diagrams for algebra of sets to clopen topological spaces. We use them as a powerful automated technique of constructing counter-models of properties the prover has a hard time proving and the user might suspect of being false. It means we propose to add a visual tool to a prover that after some fixed number of prover deductions would start constructing a visual counter-model for a property the prover is trying to prove. A prover with the visual tool is called a visual prover. The visual prover has a completeness property: for any rough set equality we can construct its proof or its counter-model

Automated deduction with associative commutative operators

We propose a new inference system for automated deduction with equality and associative commutative operators. This system is an extension of the ordered paramodulation strategy. However, rather than using associativity and commutativity as the other axioms, they are handled by the AC-unification algorithm and the inference rules. Moreover, we prove the refutational completeness of this system without needing the functional reflexive axioms or AC-axioms. Such a result is obtained by semantic tree techniques. We also show that the inference system is compatible with simplification rules

Strategy for Verifying Security Protocols with Unbounded Message Size

We present a system for automatically verifying cryptographic protocols. This system, named Casrul, manages the knowledge of principals and checks if the protocol is runnable. In this case, it outputs a set of rewrite rules describing the protocol itself, the strategy of an intruder, and the goal to achieve. The protocol specification language permits to express commonly used descriptions of properties (authentication, short term secrecy, and so on) as well as complex data structures such as tables and hash functions. The generated rewrite rules can be used for detecting flaws with various systems: theorem provers in first-order logic, on-the-fly model-checking, or SAT-based state exploration. These three techniques are being experimented in combination with Casrul in the European Union project AVISS (Automated Verification of Infinite State Systems). The aim of this paper is to describe the heart of Casrul: the model of the intruder behavior. It is based on a lazy strategy. Another advantage of our model is that it permits to handle parallel sessions and composition of keys. And for sake of completeness, we do not limit the number of sessions of the protocol to be run, nor the size of the messages sent. We have combined Casrul with the theorem prover daTac for successfully studying various protocols, such as NSPK, EKE, RSA, Neumann-Stubblebine, Kao-Chow, and Otway-Rees. We detail some of these examples in this paper. We are now studying the SET protocol and have already very encouraging results

Compiling and Verifying Security Protocols

We propose a direct and fully automated translation from standard security protocol descriptions to rewrite rules. This compilation defines non-ambiguous operational semantics for protocols and intruder behavior: they are rewrite systems executed by applying a variant of ac-narrowing. The rewrite rules are processed by the theorem-prover DATAC. Multiple instances of a protocol can be run simultaneously as well as a model of the intruder (among several possible). The existence of flaws in the protocol is revealed by the derivation of an inconsistency. Our implementation of the compiler CASRUL, together with the prover DATAC, permitted us to derive security flaws in many classical cryptographic protocols