Three applications of Spectral gaps/Expander graphs in cryptography Ramarathnam Venkatesan Microsoft Research, Redmond and Bangalore. 28-09-06 Abstract There are three questions: 1. Does the classic Pollard Rho find discrete log in |G|^{0.5} time on an abelian group G? 2. Do all elliptic curves of the same order have the same difficulty of discrete log? 3. How to build a stream cipher that is word based rather than byte based like the ubiquitous RC4? I outline some answers to these questions, all involving spectral gaps. Item 2 uses the Extended Riemann Hypothesis. Joint works with Stephen Miller (Rutgers) (1) and (2) and (3), David Jao (Waterloo) (2), Ilya Mironov (Microsoft) (3), Natan Keller (Hebrew) (3).
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