307 digit number factored

[Perry E. Metzger]

Quoting the original article:

   A mighty number falls

   Mathematicians and number buffs have their records. And today, an
   international team has broken a long-standing one in an impressive
   feat of calculation.

   On March 6, computer clusters from three institutions \u2013 the
   EPFL, the University of Bonn and NTT in Japan -- reached the end of
   eleven months of strenuous calculation, churning out the prime
   factors of a well-known, hard-to-factor number that is a whopping
   307 digits long.

   "This is the largest 'special' hard-to-factor number factored to
   date," explains EPFL cryptology professor Arjen Lenstra. (The
   number is 'special' because it has a special mathematical form --
   it is close to a power of two.) The news of this feat will grab the
   attention of information security experts and may eventually lead
   to changes in encryption techniques.


http://www.physorg.com/news98962171.html

My take: clearly, 1024 bits is no longer sufficient for RSA use for
high value applications, though this has been on the horizon for some
time. Presumably, it would be a good idea to use longer keys for all
applications, including "low value" ones, provided that the slowdown
isn't prohibitive. As always, I think the right rule is "encrypt until
it hurts, then back off until it stops hurting"...

-- 
Perry E. Metzger		perry at piermont.com

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