> ------- Start of forwarded message -------
> From: David Hopwood <###@###.###>
> Newsgroups: comp.lang.java.security
> Subject: Re: Algorithm behind java.math.BigInteger isProbablePrime
> Date: Thu, 16 Apr 1998 19:01:39 +0100
> Message-ID: <###@###.###>
> References: <###@###.###>
>
> -----BEGIN PGP SIGNED MESSAGE-----
>
> In message <###@###.###>
> Twan van der Schoot <###@###.###> wrote:
>
> > Dear Reader,
>
> > Can someone tell me which algorithm is used in the probabilistic
> > primality test in java.lang.BigInteger isProbablyPrime()?
>
> > I guess it is Miller-Rabin. Is this correct?
>
> Yes, although there is a bug in the implementation:
>
> public boolean isProbablePrime(int certainty) {
> /*
> * This test is taken from the DSA spec.
> */
> int n = certainty/2;
> if (n <= 0)
> return true;
>
> should be changed to:
>
> public boolean isProbablePrime(int certainty) {
> /*
> * This test is taken from the DSA spec.
> */
> int n = certainty/2;
> if (certainty % 2 == 1)
> n++;
> if (n <= 0)
> return true;
>
> This doesn't make a great deal of difference for typical certainty
> values, but it is annoying (especially since I pointed it out to
> JavaSoft several months ago, and they don't appear to have done anything
> about it).
>
> - --
> David Hopwood <###@###.###>
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