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CESG Seminar: Quantifying multi-user computational security

March 11, 2016 @ 4:00 pm - 5:00 pm

Room 236C WEB

Dr. Ken Duffy/ Professor at the Hamilton Institute, National
University of Ireland Maynooth

Abstract: The talk explores the connection among computational security, probability and information theory. The security of many systems is predicated on the following logic: a user selects a string, for example a password, from a list; an inquisitor who knows the list can query each string in turn until gaining access by chancing upon the user’s chosen string; the resulting system is deemed to be computationally secure so long as the list of strings is large.

Implicit in that definition is the assumption that the inquisitor knows nothing about the likely nature of the selected string. If instead one assumes that the inquisitor knows the probabilities with which strings are selected, then the random variable of interest is dubbed Guesswork, the number of queries required to identify a stochastically selected string, and the quantification of computational security becomes substantially more involved.

We will review the seminal work of J. Massey (1994) and E. Arikan (1996) on the moments of Guesswork before describing some of our contributions, which start by establishing a Large Deviation Principle (LDP) for Guesswork, which enables direct estimates of the Guesswork distribution. As the LDP is a covariant property, it facilitates a significant broadening of the remit of Guesswork to include the computational security of multi-user systems. These developments, as well as others related to information theoretic security, will be discussed. No prior knowledge of the subject will be assumed.

This talk is based on work with M. Christiansen (Maynooth), F. du
Pin Calmon (MIT) and M. Medard (MIT).

Bio: Ken Duffy is a Professor at the Hamilton Institute, National University of Ireland Maynooth. He received the B.A.(mod) and Ph.D. degrees in mathematics from Trinity College Dublin in 1996 and 2000,respectively. His research interests are in probability and statistics, and their application to engineering and the life sciences. Amongst other things, he is currently working on fundamental models of computational security, as well as DNA-coded randomised algorithms for inference in cell biology.

Host: Dr. Duffield



March 11, 2016
4:00 pm - 5:00 pm