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Title: Secrecy in two-way channels: An information theoretic prospective

Speaker: Aly El Gamal

Abstract: In 1948, Claude Shannon defined the notion of reliable rate of communication from a source to a destination as the rate at which the maximal probability of error over all possible codewords can be made arbitrarily small under no delay limitations. The maximum of such rates was named as the capacity of the channel and its relation to the mutual information between the two random variables denoting the input and output of the channel was proved.

He then studied secrecy systems, where he introduced the notion of perfect secrecy. In this work, the possibility of characterizing the security of a system regardless of the strategy used by the eavesdropper was introduced through the definition of equivocation at the eavesdropper as the uncertainty (entropy) of the original message given the observation, and perfect secrecy is achieved when this value equals the unconditional entropy of the original message.

In this talk, we consider a communication system with two users, each of which has a transmitter and a receiver. The two users intend to interchange messages, while satisfying both reliability and secrecy constraints, in the presence of a passive eavesdropper Eve without sharing a secret key a priori. Natural applications to this problem arise in Ad-hoc networks where low complexity security approaches are desired. This requirement is needed in wireless settings due to the presence of power limitations, especially for portable and small devices such as the case in Wireless Sensor Networks.

We consider newly developed coding schemes for the two way wiretap channel. The key idea is to allow the two users to randomize their transmissions by inserting artificial noise, or what we call a prefix channel. Classical information theoretic techniques are then used to exploit the created secrecy advantage with respect to Eve’s channel. As we conclude in the sequel, through numerical and experimental results, the underlying ideas can offer non-trivial advantages in certain practical applications, e.g. Wireless Body Area Networks.

Speaker Bio

Aly El Gamal received the B.Sc. in Computer Engineering from Cairo University in 2007, M.Sc. in Wireless Communications from Nile University in 2009. This talk is about the topic of my M.Sc. thesis. I had internships in Ohio State University in summer ’05 and ’06, where I was involved in implementing a light-weight reliable data collection protocol for wireless sensor networks. My research interests usually lie in the areas of information theory, coding for wireless networks, communication systems, and artificial intelligence.