809 research outputs found
APTE: An Algorithm for Proving Trace Equivalence
No full textThis paper presents APTE, a new tool for automatically proving the security of cryptographic protocols. It focuses on proving trace equivalence between processes, which is crucial for specifying privacy type properties such as anonymity and unlinkability.
The tool can handle protocols expressed in a calculus similar to the applied-pi calculus, which allows us to capture most existing protocols that rely on classical cryptographic primitives. In particular, APTE handles private channels and else branches in protocols with bounded number of sessions. Unlike most equivalence verifier tools, APTE is guaranteed to terminate
Moreover, APTE is the only tool that extends the usual notion of trace equivalence by considering ``side-channel'' information leaked to the attacker such as the length of messages and the execution times. We illustrate APTE on different case studies which allowed us to automatically (re)-discover attacks on protocols such as the Private Authentication protocol or the protocols of the electronic passports
Lengths May Break Privacy – Or How to Check for Equivalences with Length
No full textSecurity protocols have been successfully analyzed using symbolic models, where messages are represented by terms and protocols by processes. Privacy properties like anonymity or untraceability are typically expressed as equivalence between processes. While some decision procedures have been proposed for automatically deciding process equivalence, all existing approaches abstract away the information an attacker may get when observing the length of messages.
In this paper, we study process equivalence with length tests. We first show that, in the static case, almost all existing decidability results (for static equivalence) can be extended to cope with length tests.
In the active case, we prove decidability of trace equivalence with length tests, for a bounded number of sessions and for standard primitives. Our result relies on a previous decidability result from Cheval et al (without length tests). Our procedure has been implemented and we have discovered a new flaw against privacy in the biometric passport protocol
Sur un syndrome de vasodilatation paroxystique du cheval en course
No full textDarraspen Ernest Vincent, Lescure Francis. Sur un syndrome de vasodilatation paroxystique du Cheval en course. In: Bulletin de l'Académie Vétérinaire de France tome 117 n°9, 1964. pp. 423-426
Secure Refinements of Communication Channels
No full textIt is a common practice to design a protocol (say Q) assuming some secure channels. Then the secure channels are implemented using any standard protocol, e.g. TLS. In this paper, we study when such a practice is indeed secure.
We provide a characterization of both confidential and authenticated channels. As an application, we study several protocols of the literature including TLS and BAC protocols. Thanks to our result, we can consider a larger number of sessions when analyzing complex protocols resulting from explicit implementation of the secure channels of some more abstract protocol Q
Proving More Observational Equivalences with ProVerif
No full textThis paper presents an extension of the automatic protocol verifier ProVerif in order to prove more observational equivalences. ProVerif can prove observational equivalence between processes that have the same structure but differ by the messages they contain. In order to extend the class of equivalences that ProVerif handles, we extend the language of terms by defining more functions (destructors) by rewrite rules. In particular, we allow rewrite rules with inequalities as side-conditions, so that we can express tests ''if then else'' inside terms. Finally, we provide an automatic procedure that translates a process into an equivalent process that performs as many actions as possible in- side terms, to allow ProVerif to prove the desired equivalence. These extensions have been implemented in ProVerif and allow us to au- tomatically prove anonymity in the private authentication protocol by Abadi and Fournet
Spinal stenosis: A summary and review
No full textA review of the etiology, clinical, radiological and laboratory presentation, differential diagnosis and management of spinal stenosis is presented.
Keywords: Spinal stenosis, central stenosis, lateral recess stenosis, back pain, chiropracti
Le cheval dans le monde romain
No full textVoici un petit livre « grand public », fort bien fait et entièrement consacré au cheval durant l’Antiquité romaine. Ses deux auteurs principaux sont, pour l’une, professeur certifié et en thèse sur l’élevage des chevaux durant l’Antiquité tardive (Amandine Cristina) et, pour l’autre, archéologue au service d’archéologie du conseil général du Calvados (Vincent Hincker). Ils se sont en outre associés à plusieurs spécialistes des sources archéologiques, archéo..
Tests for Establishing Security Properties
No full textEnsuring strong security properties in some cases requires participants to carry out tests during the execution of a protocol. A classical example is electronic voting: participants are required to verify the presence of their ballots on a bulletin board, and to verify the computation of the election outcome. The notion of certificate transparency is another example, in which participants in the protocol are required to perform tests to verify the integrity of a certificate log.
We present a framework for modelling systems with such `testable properties', using the applied pi calculus. We model the tests that are made by participants in order to obtain the security properties. Underlying our work is an attacker model called ``malicious but cautious'', which lies in between the Dolev-Yao model and the ``honest but curious'' model. The malicious-but-cautious model is appropriate for cloud computing providers that are potentially malicious but are assumed to be cautious about launching attacks that might cause user tests to fail
Automating Security Analysis: Symbolic Equivalence of Constraint Systems
No full textWe consider security properties of cryptographic protocols, that are either trace properties (such as confidentiality or authenticity) or equivalence properties (such as anonymity or strong secrecy). Infinite sets of possible traces are symbolically represented using deducibility constraints. We give a new algorithm that decides the trace equivalence for the traces that are represented using such constraints, in the case of signatures, symmetric and asymmetric encryptions. Our algorithm is implemented and performs well on typical benchmarks. This is the first implemented algorithm, deciding symbolic trace equivalence
Les investissements directs français à l’étranger et l’emploi en France
No full textThe influence of direct foreign investment (DFI) on wage and employment levels is theoretically ambiguous. On the other hand, according to statistical data, French DFI forms part of a strategy to gain market shares abroad : the majority of DFI is in the tertiary sector and in OECD countries. Empirical studies have confirmed that labour cost is a secondary factor in the decision to set up abroad. Moreover, wage and employment levels in the parent company seem to be positively correlated with the activity of its foreign subsidiaries. Although it does not appear to act as a substitute for domestic investment, outward investment nevertheless seems to have a positive impact on export levels.L’influence de l’investissement direct à l’étranger (IDE) sur les niveaux d’emploi et de salaires est théoriquement équivoque. En revanche, d’après les données statistiques, l’IDE français s’inscrit dans une stratégie de conquête de parts de marché à l’étranger : la majorité des IDE est réalisée dans le secteur des services et à destination des pays de l’OCDE. Les études empiriques confirment que le coût du travail est un facteur secondaire de la décision d’implantation à l’étranger. Le niveau de l’emploi et des salaires dans la maison mère apparaît d’ailleurs positivement corrélé avec l’activité des filiales à l’étranger. S’il ne semble pas y avoir substitution avec l’investissement domestique, l’investissement sortant semble au contraire exercer une influence positive sur le niveau des exportations.Aussilloux Vincent, Cheval Marie-Laure. Les investissements directs français à l’étranger et l’emploi en France. In: Économie & prévision, n°152-153, 2002-1-2. Commerce international. pp. 171-188
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