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International audience; The Lightning Network is a second layer technology running on top of Bitcoin and other Blockchains. It is composed of a peer-to-peer network, used to transfer raw information data. Some of the links in the peer-to-peer network are identified as payment channels, used to conduct payments between two Lightning Network clients (i.e., the two nodes of the channel). Payment channels are created with a fixed credit amount, the channel capacity. The channel capacity, together with the IP address of the nodes, is published to allow a routing algorithm to find an existing path between two nodes that do not have a direct payment channel. However, to preserve users' privacy, the precise balance of the pair of nodes of a given channel (i.e. the bandwidth of the channel in each direction), is kept secret. Since balances are not announced, second-layer nodes probe routes iteratively, until they find a successful route to the destination for the amount required, if any. This feature makes the routing discovery protocol less efficient but preserves the privacy of channel balances. In this paper, we present an attack to disclose the balance of a channel in the Lightning Network. Our attack is based on performing multiple payments ensuring that none of them is finalized, minimizing the economical cost of the attack. We present experimental results that validate our claims, and countermeasures to handle the attack.

A medium access control protocol based on quantum entanglement has been introduced by Berces and Imre (2006) and Van Meter (2012). This protocol entirely avoids collisions. It is assumed that the network consists of one access point and two client stations. We extend this scheme to a network with an arbitrary number of client stations. We propose three approaches, namely, the qubit distribution, transmit first election and temporal ordering protocols. The qubit distribution protocol leverages the concepts of Bell-EPR pair or W state triad. It works for networks of up to four CSs. With up to three CSs, there is no probability of collision. In a four-CS network, there is a low probability of collision. The transmit first election protocol and temporal ordering protocols work for a network with any number of CSs. The transmit first election builds upon the concept of W state of size corresponding to the number of client stations. It is fair and collision free. The temporal ordering protocol employs the concepts of Lehmer code and quantum oracle. It is collision free, has a normalized throughput of 100% and achieves quasi-fairness., 18 pages, 12 figures, 3 tables; manuscript under review

International audience; In this paper, we propose a Hybrid Multi-Channel Multi-hop Medium Access Control (HMM-MAC) meeting the safety and non-safety requirements in Vehicular Ad-hoc Networks when no infrastructure is present (V2V communication) with only a single transceiver at each vehicle. The simulation results showed that our scheme could achieve a higher delivery ratio of road safety messages and a high probability to select a free transmission channel in a certain region and during a certain time

International audience; In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. The Link Quality Indicator (LQI) is defined in the 802.15.4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. However, the challenge of clustering mechanisms is to form the smallest number of clusters by maximizing distances separating cluster heads to provide an efficient cover of the network and also minimizes the cluster overlaps. This reduces the amount of channel contention between clusters, and also improves the efficiency of algorithms that run at the level of the cluster heads. Therefore we propose an analytical model based on the use of the LQI in order to derive an optimally one-dominating set in which the smaller distance separating two cluster heads is improved

The Link Quality Indicator (LQI) is defined in the 802.15.4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. However, in cluster formation, it is quite important to sufficiently outspread the clusterheads (or caryommes) in order to improve the network efficiency. Therefore we propose a LQI based d-clustering protocol (LQIDCP) which produces clusters of which each clusterhead has a better positioning regarding the locations of other clusterheads. Simulation results show that the caryommes resulting from LQIDCP are sufficiently outspread. LQI-DCP also reduces the density of clusterheads and then improves the WSN energy efficiency, while each sensor remains still at less than d-hops from a caryomme

International audience; This article provides a historical look at the past four years of nanosatellites launch activity. In this period, there were recorded 55 nanosatellites launches, 16 of them were lost in 26th July 2006, as the launcher Dnepr-1 has exploded 86 seconds after launch.This paper presents an analysis of the nanosatellites launches in the period 2004 - 2007, based on the following criteria: the owner country of the payload, mass and mission category, type of orbit, type of launcher, spaceport, mission status and type of activity

The increasing commercialization of manned and unmanned space travel as well as ever more ambitious missions for the scientific investigation of the solar system and far space require the development of more efficient, more economical and more resistant space technologies and systems in the future. The main aim of this study is to carry out a general overview of nanosatellite systems, explaining the application potential of nanosatellites in the future space missions. In the first chapter of this paper, we present the applications of nanosatellites and their advantages and limitations in comparison with the traditional satellites. Analysis of the evolution of the nanosatellites launches in the last 18 years shows an ascendant trend as a result of the increasing nanosatellites launches especially in the last 7 years. In the second chapter, we present four nanosatellites programs developed by different universities : CanX program, ION-F program, the Munin nanosatellite and the QuakeSat nanosatellite. A summary of the nanosatellite programs developed in different countries is also included. The third chapter includes a comporative analysis of nanosatellite systems and the last chapter of this study presents the trends in the nanosatellite domain

Telecommunication is critical at all phases of disaster management. The real-time information before, during and after emergencies would be very valuable in-order to provide emergency services. Due to the development of new low cost satellite systems like nano, pico satellite, there exist a feasible option in providing satellite system in rural area where existing telecommunication infrastructure is indadequate or non-existent. There are various challenges in performance of the on-board satellites system, mainly storage. Hence there exist a need for good buffer management policy to improve the performance of the system. We show that adaptive buffer management optimally exploit the limited onboard resource (buffer size) and therefore to maximize the science return