Article View: sci.crypt
Article #938Re: RSA-129 contest
From: D. J. Bernstein
Date: Fri, 21 Aug 1992 23:30
Date: Fri, 21 Aug 1992 23:30
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2367 bytes
In article <9208200145.AA29470@ucbvax.Berkeley.EDU> jbs@WATSON.IBM.COM writes: > What is the point of this contest? To find a good polynomial for RSA-129. To factor RSA-129 with GNFS would take many hundreds or thousands of MIPS-years with a random polynomial. In the two weeks since the contest was announced, quite a few people have submitted polynomials, and the best so far---yours---is roughly 1000 times better than random. That means *three times less work* for GNFS. That is a huge difference. Polynomials another 10 or 20 times better could well be good enough for GNFS to complete in a reasonable time. There are also algebraic criteria which give some polynomials a significant ``boost.'' For instance, a polynomial which has many roots modulo 3, 5, and 7 is nearly 100 times better than a polynomial which has no roots modulo 3, 5, or 7, all else being equal. (Most polynomials are somewhere in the middle.) Keep in mind that f(m) doesn't have to equal n---it be any positive multiple. So there are a huge number of polynomials to search through. Someone who uses clever techniques to search through selected m's may have a better chance of finding a good polynomial than someone who runs through billions of m's by brute force (though brute force never hurts!). It may also be possible to use the extra structure of two-variable polynomials f(m_1,m_2) to obtain better results there--- certainly the optimal two-variable polynomials have much smaller coefficients than the optimal one-variable polynomials. These are open problems. Nobody knows what the best way to search for polynomials is. In any case, the polynomial-searching contest has produced spectacular results so far. Keep those submissions coming in! I'm sorry I don't yet have precise estimates of exactly how much RSA-129 GNFS time is saved by any particular polynomial, but I can assure you that a few weeks of polynomial searching will be time very, very well spent. ---Dan
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Path: arc1-ca.pugleaf.net!sparky!uunet!usc!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!ucbvax!virtualnews.nyu.edu!brnstnd From: brnstnd@nyu.edu (D. J. Bernstein) Newsgroups: sci.crypt Subject: Re: RSA-129 contest Message-ID: <5801.Aug2123.30.1592@virtualnews.nyu.edu> Date: 21 Aug 92 23:30:15 GMT References: <9208200145.AA29470@ucbvax.Berkeley.EDU> Organization: IR Lines: 37