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From: Bram Cohen (bramgawth.com)
Date: Thu May 24 2001 - 20:43:19 CDT
On 24 May 2001, lcs Mixmaster Remailer wrote:
> What is the best way to find a prime p for which (p-1)/2 is also prime?
> Some people seem to have very fast algorithms.
I found the one I posted the other day just by scan searching and using
amkCrypto's isPrime() function.
isPrime works by first checking for a bunch of small factors and if none
are found doing one of the probabilistic primality tests. I probably could
have speeded it up a lot by doing the sieve on both n and (n-1)/2 before
doing the stronger check on either of them, but other than that I don't
know any special speedup tricks.
"Markets can remain irrational longer than you can remain solvent"
-- John Maynard Keynes