Secret message capacity of a line network

We investigate the problem of information theoretically secure communication in a line network with erasure channels and state feedback. We consider a spectrum of cases for the private randomness that intermediate nodes can generate, ranging from having intermediate nodes generate unlimited private randomness, to having intermediate nodes generate no private randomness, and all cases in between. We characterize the secret message capacity when either only one of the channels is eavesdropped or all of the channels are eavesdropped, and we develop polynomial time algorithms that achieve these capacities. We also give an outer bound for the case where an arbitrary number of channels is eavesdropped. Our work is the first to characterize the secrecy capacity of a network of arbitrary size, with imperfect channels and feedback. As a side result, we derive the secret key and secret message capacity of an one-hop network, when the source has limited randomness

Corruption: Democracy, Autocracy, and Political Stability

The recent empirical literature on corruption has identified a long list of variables that correlate significantly with corruption but only five were distinguished by Leamer’s Extreme Bounds Analysis as robust to various samples, measures of corruption, and regression specifications. Among these five factors that were found to reduce corruption are decades-long tradition of democracy and political stability. In today’s world, however, there are many countries that combine one of these two robust determinants of corruption with the opposite of the other: politically stable autocracies or newly formed and unstable democracies. The central question raised in this paper is: Is it worth, in terms of corruption, for a country to trade stability with autocratic rule for political freedoms but with transitional instability? We find that the answer to this question is in the affirmative - the level of corruption is indeed lower in unstable democracies than in stable dictatorships. Our results are robust to various measures of corruption, alternative regressor indices, and regression specifications.corruption, democracy, autocracy, dictatorship, political stability

Intellectual Property Protection and Innovation

Well-designed and enforceable intellectual property rights (IPRs) provide economic incentives for research and development (R&D). Despite the apparent benefits to the existence of strong IPRs, many countries have a poor record in IPR protection. This paper develops a game-theoretic model of heterogeneous producers and endogenous innovators to analyze the causes and consequences of IPR infringement. Analytical results show that IPR infringement affects pricing and welfare in the market. The optimal IPR protection for the government depends not only on the pricing decision of the innovator, but also on its country size and its conjecture about the policy of other governments. A government can only use IPR protection as a strategic trade policy tool if the innovator can price discriminate.Research and Development/Tech Change/Emerging Technologies,

LP formulations for secrecy over erasure networks with feedback

We design polynomial time schemes for secure message transmission over arbitrary networks, in the presence of an eavesdropper, and where each edge corresponds to an erasure channel with public feedback. Our schemes are described through linear programming (LP) formulations, that explicitly select (possibly different) sets of paths for key-generation and message sending. Although our LPs are not always capacity-achieving, they outperform the best known alternatives in the literature, and extend to incorporate several interesting scenaria

Tensile force measurement by image processing

The Sometimes unexpected overloads start up in multi sheave friction drives which could cause the breakage of the wire rope.To analyze the breakage and the overload process a 7 sheaves examiner machine was developed and built. Since the visual measuringprocess provides several good advantages in this machine a spring is used instead of wire rope. At the beginning the distance of threadsand pixels (in the picture) were measured manually. The aim of this paper is to show the automation method of the visual measuringprocess by the Matlab software in the Image Processing Toolbox

Secret Communication over Broadcast Erasure Channels with State-feedback

We consider a 1-to-$K$ communication scenario, where a source transmits private messages to $K$ receivers through a broadcast erasure channel, and the receivers feed back strictly causally and publicly their channel states after each transmission. We explore the achievable rate region when we require that the message to each receiver remains secret - in the information theoretical sense - from all the other receivers. We characterize the capacity of secure communication in all the cases where the capacity of the 1-to-$K$ communication scenario without the requirement of security is known. As a special case, we characterize the secret-message capacity of a single receiver point-to-point erasure channel with public state-feedback in the presence of a passive eavesdropper. We find that in all cases where we have an exact characterization, we can achieve the capacity by using linear complexity two-phase schemes: in the first phase we create appropriate secret keys, and in the second phase we use them to encrypt each message. We find that the amount of key we need is smaller than the size of the message, and equal to the amount of encrypted message the potential eavesdroppers jointly collect. Moreover, we prove that a dishonest receiver that provides deceptive feedback cannot diminish the rate experienced by the honest receivers. We also develop a converse proof which reflects the two-phase structure of our achievability scheme. As a side result, our technique leads to a new outer bound proof for the non-secure communication problem

On the Strong Parity Chromatic Number

International audienceA vertex colouring of a 2-connected plane graph G is a strong parity vertex colouring if for every face f and each colour c, the number of vertices incident with f coloured by c is either zero or odd. Czap et al. [Discrete Math. 311 (2011) 512-520] proved that every 2-connected plane graph has a proper strong parity vertex colouring with at most 118 colours. In this paper we improve this upper bound for some classes of plane graphs

Parity vertex colouring of plane graphs

AbstractA proper vertex colouring of a 2-connected plane graph G is a parity vertex colouring if for each face f and each colour c, either no vertex or an odd number of vertices incident with f is coloured with c. The minimum number of colours used in such a colouring of G is denoted by χp(G).In this paper, we prove that χp(G)≤118 for every 2-connected plane graph G