Decentralized Federated Learning (DFL) has garnered attention for its robustness and scalability compared to Centralized Federated Learning (CFL). While DFL is commonly believed to offer privacy advantages due to the decentralized control of sensitive data, recent work by Pasquini et, al. challenges this view, demonstrating that DFL does not inherently improve privacy against empirical attacks under certain assumptions. For investigating fully this issue, a formal theoretical framework is required. Our study offers a novel perspective by conducting a rigorous information-theoretical analysis of privacy leakage in FL using mutual information. We further investigate the effectiveness of privacy-enhancing techniques like Secure Aggregation (SA) in both CFL and DFL. Our simulations and real-world experiments show that DFL generally offers stronger privacy preservation than CFL in practical scenarios where a fully trusted server is not available. We address discrepancies in previous research by highlighting limitations in their assumptions about graph topology and privacy attacks, which inadequately capture information leakage in FL.

International audience

International audience

International audience

International audience

International audience

International audience

Complex event processing (CEP) is a technique for analyzing and correlating large amount of information about events that happen in a timely manner, and being in a position to derive conclusions or even respond to them as quickly as possible. Complex events are raised based on incoming sources productions and according to a set of user-defined rules. However, as the complexity of CEP systems grow, the process for manually defining rules becomes time and resource consuming or even impossible as dynamic changes occur in the domain environment. Moreover, it restricts the use of CEP to merely the detection of straightforward situations than in more advanced fields that require earliness and prediction. Therefore, we present a novel approach for completing the supervision of an unsupervised structure learning task. More precisely, we propose to incorporate an unsupervised technique that derives labels for unlabelled data, depended on their distance. From these results, we automatically generate CEP rules to feed the system. In order to evaluate our approach, we used a real world data-set with data labeled by experts. The evaluation indicates that our approach can effectively complete the missing labels and, in some cases, improve the accuracy of the underlying CEP structure learning system.

The mobile ad-hoc networks (MANETs) represent a broad area of study and market interest. They provide a wide set of applications in multiple domains. In that context, the functional and non-functional monitoring of these networks is crucial. For that purpose, monitoring techniques have been deeply studied in wired networks using gossip-based or hierarchical-based approaches. However, when applied to a MANET, several problematics arise mainly due to the absence of a centralized administration, the inherent MANETs constraints and the nodes mobility. In this paper, we present a hybrid distributed monitoring architecture for mobile adhoc networks in context of mobility pattern. We get inspired of gossip-based and hierarchical-based algorithms for query dissemination and data aggregation. We define gossip-based mechanisms that help our virtual hierarchical topology to complete the data aggregation, and then ensure the stability and robustness of our approach in dynamic environments. Further, we propose a fully distributed monitoring protocol that ease the nodes communications. We evaluate our approach through a simulated testbed by using NS3 and Docker, and illustrate the efficiency of our mechanisms.

Monitoring techniques have been deeply studied in wired networks using gossip and hierarchical approaches. However, when applied to a MANET, several problematics arise. We present a hybrid distributed monitoring architecture for MANETs. We get inspired of gossip-based and hierarchical-based algorithms for query dissemination and data aggregation. We define gossip-based mechanisms that help our virtual hierarchical topology to complete the data aggregation, and then ensure the stability and robustness of our approach in dynamic environments. We propose a fully distributed monitoring protocol that ease the nodes communications. We evaluate our approach by using NS3 and Docker.

Collaborative systems are growing in use and in popularity. The need to boost the methods concerning the interoperability is growing as well, therefore, trustworthy interactions of the different systems are a priority. We have proposed a formal distributed network monitoring approach to analyze the packets exchanged by the entities, in order to prove a system is acting in a trustworthy manner. Using this approach, some limitations regarding the testers resources have been found. In this paper, we identify the constraints and propose and new language suited for testing at runtime in different environments.

International audience

Wireless Ad hoc Networks are rapidly growing in popularity because of their flexibility and wide range of applications (Indoor Communications, Intelligent Transportation, Emergency Operations, Public Safety, etc.). However, while it becomes easier to set up such networks, one of the main constraints is the heterogeneity of the nearby devices (or nodes). Moreover, it is still very difficult to make them communicate if these nodes use different routing protocols. In this paper, we present a novel approach that makes use of layer 3 protocols to guarantee interoperability between networks. We introduce the notion of Strip Interoperability, a new mechanism that aims to address this problem by creating a bridge between heterogeneous wireless ad hoc networks. An implementation of our approach through a real case study is shown to illustrate the applicability of our mechanism.

Monitoring for passive conformance testing is a way of checking if the system meets its requirements. Several formal approaches have been proposed these last years, but most of them only consider the control portion of the protocol neglecting the data portions, or are confronted with an overloaded amount of data values to consider. In this work, we propose a novel approach to define protocol properties in terms of Input-Output Symbolic Transition Systems (IOSTS) and show how they can be tested on real execution traces taking into account the data and control portions. These properties can be designed to test the conformance of a protocol as well as security aspects. A parametric trace slicing approach is defined to match trace and property. Besides, a prototype is here developed and experimented. Our approach is illustrated by its application to a set of real execution traces extracted from a real automotive Bluetooth framework with functional and security properties.

International audience

By applying formal description techniques and formal testing approaches, it is possible to validate the conformance of implementations to the requirements of communication protocols. However, and particularly in wireless communications systems, most of the testing work is devoted to the evaluation of their performance in a simulated environment without formal descriptions. The current work expands on our formal approach for black-box testing of network protocols implemented in the tool DataMonitor, and it demonstrates its applications for MANET routing protocols through passive testing on OLSR traces. With such application, we show how our formal approach can help express complex properties from data relations in messages and evaluated them on real traces. The results from our experiments with an OLSR implementation are provided.

As the Digital Ecosystems are growing in use and in popularity, the need to boost the methods concerned by their interoperability is growing as well; making thus trustworthy interactions of the different agents (e.g., network systems) a priority. In our work, we focus on "soft trust", that is trust management systems that can be based on experience and reputation. Each trust system defines how they evaluate the trustee experience. The observations of the trustee behaviors are added to the trustee experience. Furthermore, most of the works dedicated to trust estimations in different kinds of ecosystems are based on local observations through monitored entities. No formal approaches have been defined for distributed monitored elements by considering several points of observations. This is what we intend in this work. We propose to use distributed network monitoring techniques to analyze the packets that the truster and trustee exchange in order to prove the trustee is acting in a trustworthy manner. A formal approach is defined to express trust properties and to evaluate them on real execution traces. Our approach is applied on DNS traces for assessing the trust among the entities.

There is currently a high level of consciousness of the importance and impact of formally testing communicating networks. By applying formal description techniques and formal testing approaches, we are able to validate the conformance of implementations to the requirements of communication protocols. In this context, passive testing techniques are used whenever the system under test cannot be interrupted or access to its interfaces is unavailable. Under such conditions, communication traces are extracted from points of observation and compared to the expected behavior formally specified as properties. Since most works on the subject come from a formal model context, they are optimized for testing the control part of the communication with a secondary focus on the data parts. In the current work, we provide a data-centric approach for black-box testing of network protocols. A formalism is provided to express complex properties in a bottom-up fashion starting from expected data relations in messages. A novel algorithm is provided for evaluation of properties in protocol traces. Experimental results on Session Initiation Protocol (SIP) traces for IP Multimedia Subsystem (IMS) services are provided.

This paper deals with the crucial challenging issue of testing the conformance of the MANET routing protocols. Indeed, because of the inherent constraints of such networks such as a dynamic topology, to formally test these protocols becomes a tough problem. Most of the studies taking into account a formal model of the protocol is faced to the combinatorial state space explosion issue when deploying and analyzing that model. In our work we present how to cope with that problem by drawing inspiration of the model-checker research domain and an integration of a component-based testing algorithm dedicated to the automatic generation of OLSR test sequences from a formal model written in Promela.

The Internet is a composition of ASes (Autonomous Systems), BGP (Border Gateway Protocol) is the routing protocol that is responsible of exchanging routes between these ASes. It operates in two modes: eBGP (External BGP) and iBGP (Internal BGP). EBGP exchanges routing information between ASes, while iBGP propagates that information within the AS. IBGP node has not the ability to reflect routes. Therefore, each internal node should have iBGP sessions with all ASBRs (Autonomous System Border Routers). BGP route reflection was widely employed as an alternative to full mesh solution to reduce the needed number of iBGP sessions and, in turn, increase the scalability inside the AS. Under particular configuration, BGP scaling mechanism defined in route reflection mechanism introduces persistent route oscillation, forwarding loops, and non-optimal egress nodes. We propose the PC-iBGP (Partial Complete iBGP) as an alternative to the route reflection approach. PC- iBGP nodes have the ability of reflecting routes. It eliminates the use of clusters and establishes iBGP sessions only between single hop neighbors. We prove that it holds sufficient correctness conditions as well as its robustness against failures, asymmetric path problem, and MED (Multi Exit Discriminator) induced oscillations.

The service-oriented approach is becoming more and more popular to integrate highly heterogeneous systems. Web services are the natural evolution of conventional middleware technologies to support Web-based and enterprise level integration. Formal testing of such Web-based technology is a key point to guarantee its reliability. In this paper, we choose a non-intrusive approach based on monitoring to propose a conformance passive testing methodology to check that a composed Web service respects its functional requirements. This methodology is based on a set of formal invariants representing properties to be tested including data and time constraints. Passive testing of an industrial system (that uses a composition of Web services) is briefly presented to demonstrate the effectiveness of the proposed approach.

The Internet is a composition of ASes (Autonomous Systems), BGP (Border Gateway Protocol) is the routing protocol that is responsible of exchanging routes between these ASes. It operates in two modes: External BGP (eBGP) and Internal BGP (iBGP). EBGP exchanges routing information between ASes, while iBGP propagates that information within the AS. BGP Full Mesh Solution (FMS) is based on that all the ASBRs (Autonomous System Border Routers) should be fully meshed and each internal node should have an iBGP session with all of them. This was because an iBGP node does not have the ability to reflect routes. BGP route reflection was widely employed as an alternative to full mesh to reduce the needed number of iBGP sessions and, in turn, increase the scalability inside the AS. Under particular configuration, it introduces persistent route oscillation, forwarding loops, and non-optimal egress nodes. Skeleton is an alternative to route reflection that overcomes these routing anomalies. Skeleton is a subgraph of the physical graph with the same set of nodes, its edges are the iBGP sessions between the nodes. All Skeleton nodes have the ability of reflecting routes. Skeleton eliminates the use of clusters and establishes iBGP sessions only between single hop neighbors. We prove that it holds the sufficient correctness conditions as well as its robustness against MED induced oscillations. We evaluate it on five real world topologies and find that the number of iBGP sessions has a linear relationship with the number of ASBRs, where in FMS this relationship is quadratic.

In this paper we apply a passive testing methodology to the analysis of a non-trivial system. In our framework, so-called invariants provide us with a formal representation of the requirements of the system. In order to precisely express new properties in multi-node environments, in this paper we introduce a new kind of invariants. We apply the resulting framework to perform a complete study of a MANET routing protocol: The optimized link state routing protocol.

Although the adoption of the IP Multimedia Subsystem (IMS) keeps growing, IMS applications are often integrated to the system without being formally tested. In this work, we are interested in the IMS Push over Cellular (PoC) service, an OMA standard. We propose a conformance passive testing approach to check that its implementation respects the main standard requirements. This approach is based on a set of formal invariants representing the most relevant expected properties to be tested. Two testing phases are applied: the verification of the invariants against the service specification and their testing on the PoC collected execution traces.

Several researches are currently dealing with the validation of ad hoc routing protocols. But almost all of them stress their analysis from simulation or emulation studies. We present in this paper a formal methodology for the conformance and interoperability testing of the DSR protocol based on a formal specification of the protocol designed in SDL. Difficulties in interoperability testing are illustrated and solutions are proposed.