100218: BigInteger staticRandom field (original) (raw)

Doug Lea dl at cs.oswego.edu
Thu Jan 5 17:58:32 UTC 2012

On 01/05/12 01:02, Bill Pugh wrote:

So I think the right thing to do is to abandon the original patch, and instead make the following changes:

* add the following method to BigInteger public boolean isProbablePrime(int certainty, Random end) , which allows primality testing with arbitrary Random objects. In many cases, using a well seeded normal Random object will work just fine, and this will give users the ability to provide their own Random objects * Document SecureRandom to note that all instances of SecureRandom depend on a common shared source of randomness, and thus it can be a concurrency bottlenck. * Document that BigInteger.isProbablePrime(int certainty) is a concurrency bottleneck.

This all sounds perfect to me. Joe Darcy - do you have any thoughts?

* Add java.util.concurrent.MostlySecureRandom which uses /dev/random for seeding, and uses only the SHA1PRNG implementation provided by sun.security.provider.SecureRandom to generate subsequent randomness. Feel free to pick a name other than MostlySecureRandom. After the initial seeding, calls to generate randomness using a MostlySecureRandom should not use any shared values.

I think the only question is whether, given low expected usage, it would be OK just to explain how to do this in some javadoc, and also provide in some jsr166.extras package.

-Doug

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