[RC5] Fast way of Decrypting RSA keys -- not really

Peter Cordes peter at llama.nslug.ns.ca
Sat Mar 3 18:05:49 EST 2001

On Mon, Feb 05, 2001 at 12:03:52PM -0800, Skinnee T wrote:
> http://www.mb.com.ph/INFO/2001-02/IT020201.asp
> http://www.mb.com.ph/INFO/2001-02/IT020601.asp
> Check out those two stories to see how a math guy found the answer to
> decrypting the algorithm fast.

 Correction: he _thought_ he had broken RSA.  It was a good try, but it
turns out his method is not actually fast when used on normal-sized keys.
(he'd been trying it on tiny ones.)

 Ron Rivest, in a letter to /. editor jamie, when asked what was going on:

     A fellow by the name of Leo de Velez from the Phillipines had
     thought he had broken RSA, and a reporter colleague wrote up this
     story and published it. This is probably what you have heard about.
     Mr. Velez also wrote to me with his ideas. Unfortunately for him,
     his approach is actually much *slower* than the naive approach to
     factoring by trial division by 2, 3, 4, .... His approach doesn't
     improve on any known techniques, and doesn't constitute a "break"
     of RSA at all.

     If you write to Mr. Velez (leo at teammail dot com) he will

 See the whole story at: http://slashdot.org/articles/01/02/05/1911258.shtml

 Whenever you see stories about guys who think they've figured something
out, it's a good idea to do a search and see if anyone agrees with them, or
actually comes out and shows that they've made a mistake.  Ron Rivest is the
"R" in "RSA", so it's quite likely that he's got the facts right :)

#define X(x,y) x##y
Peter Cordes ;  e-mail: X(peter at llama.nslug. , ns.ca)

"The gods confound the man who first found out how to distinguish the hours!
 Confound him, too, who in this place set up a sundial, to cut and hack
 my day so wretchedly into small pieces!" -- Plautus, 200 BCE
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