Brute force searching, the typical set and Guesswork
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Medard_Brute force.pdf
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352.25 KB
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Author(s)
Christiansen, Mark M.
Duffy, Ken R.
Medard, Muriel
Calmon, Flavio du Pin
Date Issued
July 2013
Journal
Proceedings of the 2013 IEEE International Symposium on Information Theory
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Citation
Christiansen, Mark M., Ken R. Duffy, Flavio du Pin Calmon, and Muriel Medard. “Brute Force Searching, the Typical Set and Guesswork.” 2013 IEEE International Symposium on Information Theory (July 2013).
Version
Original manuscript
Abstract
Consider the situation where a word is chosen probabilistically from a finite list. If an attacker knows the list and can inquire about each word in turn, then selecting the word via the uniform distribution maximizes the attacker's difficulty, its Guesswork, in identifying the chosen word. It is tempting to use this property in cryptanalysis of computationally secure ciphers by assuming coded words are drawn from a source's typical set and so, for all intents and purposes, uniformly distributed within it. By applying recent results on Guesswork, for i.i.d. sources it is this equipartition ansatz that we investigate here. In particular, we demonstrate that the expected Guesswork for a source conditioned to create words in the typical set grows, with word length, at a lower exponential rate than that of the uniform approximation, suggesting use of the approximation is ill-advised.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Research Laboratory of Electronics
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1109/ISIT.2013.6620428
