A birthday paradox for Markov chains, with an optimal bound for collision in the Pollard Rho algorithm for discrete logarithm

Duration: 24 mins 33 secs
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Description: Montenegro, R (Massachusetts Lowell)
Wednesday 26 March 2008, 14:35-15:05
Markov-chain Monte Carlo Methods
 
Created: 2008-04-01 14:28
Collection: Combinatorics and Statistical Mechanics
Publisher: Isaac Newton Institute
Copyright: Montenegro, R
Language: eng (English)
Credits:
Producer:  Steve Greenham
Author:  Montenegro, R
 
Abstract: We show a Birthday Paradox for self-intersections of Markov chains with uniform stationary distribution. As an application, we analyze Pollard's Rho algorithm for finding the discrete logarithm in a cyclic group G and find that, if the partition in the algorithm is given by a random oracle, then with high probability a collision occurs in order |G|^0.5 steps. This is the first proof of the correct order bound which does not assume that every step of the algorithm produces an i.i.d. sample from G.

Related Links

* http://www.ravimontenegro.com/research/prho.pdf - Preprint of the paper
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