Aslan Tchamkerten

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The Mafia fraud consists in an adversary transparently relaying the physical layer signal during an authentication process between a verifier and a remote legitimate prover. This attack is a major concern for certain RFID systems, especially for payment related applications. Previously proposed protocols that thwart the Mafia fraud treat relaying and(More)
A formulation of the problem of asynchronous point-to-point communication is developed. In the system model of interest, the message codeword is transmitted over a channel starting at a randomly chosen time within a prescribed window. The length of the window scales exponentially with the codeword length, where the scaling parameter is referred to as the(More)
We consider the ldquoone-shot frame synchronization problem,rdquo where a decoder wants to locate a sync pattern at the output of a memoryless channel on the basis of sequential observations. The sync pattern of length <i>N</i> starts being emitted at a random time within some interval of size <i>A</i>, where <i>A</i> characterizes the asynchronism level.(More)
Several aspects of the problem of asynchronous point-to-point communication without feedback are developed when the source is highly intermittent. In the system model of interest, the codeword is transmitted at a random time within a prescribed window whose length corresponds to the level of asynchronism between the transmitter and the receiver. The decoder(More)
We study a problem of broadcasting confidential messages to multiple receivers under an information-theoretic secrecy constraint. Two scenarios are considered: 1) all receivers are to obtain a common message; and 2) each receiver is to obtain an independent message. Moreover, two models are considered: parallel channels and fast-fading channels. For the(More)
Burnashev in 1976 gave an exact expression for the reliability function of a discrete memoryless channel (DMC) with noiseless feedback. A coding scheme that achieves this exponent needs, in general, to know the statistics of the channel. Suppose now that the coding scheme is designed knowing only that the channel belongs to a family Q of DMCs. Is there a(More)
The capacity per unit cost, or, equivalently, the minimum cost to transmit one bit, is a well-studied quantity under the assumption of full synchrony between the transmitter and the receiver. In many applications, such as sensor networks, transmissions are very bursty, with amounts of bits arriving infrequently at random times. In such scenarios, the cost(More)
The problem of detecting a transient change in distribution of a discrete time series is investigated when there is a constraint on the number of observed samples. Under a minimax setting where the change time is unknown, the objective is to design a statistical test that minimizes a measure of worst case delay under a constraint on the average time to(More)
Motivated by certain recent problems in asynchronous communication, we introduce and study B(n, d, w), defined as the maximum number of length n binary sequences with minimum distance d, and such that each sequence has weight at least w. Specifically, we investigate the asymptotic exponential growth rate of B(n, d, w) with respect to n and with fixed ratios(More)