On Tue, 21 Jul 2009, Jonathan Yu wrote: > On Tue, Jul 21, 2009 at 7:03 PM, Don Armstrong<[email protected]> wrote: > > $ for a in $(seq 1 20); do perl -MMath::Random=random_uniform -e 'print > > join(q( ),random_uniform(4)),qq(\n)'; done; > > 0.489988645840918 0.579920159789368 0.993361818807086 0.955731167568429 > > 0.489988645840918 0.579920159789368 0.993361818807086 0.955731167568429 > > Maybe a simpler solution (which doesn't require changes to the local > Math::Random) would be to use a module like Math::TrulyRandom to get > some truly random data, or otherwise get the data from, say, > /dev/random, to use as your seed. You can then set Math::Random's > seed using random_set_seed(@seed)
Yeah; that's certainly one way of fixing it locally. > > It should instead call Perl_seed to generate the random number in > > XS. I'll probably send in a patch in a bit which does this. [I > > probably won't bother to make it compatible with pre 5.8 versions > > of perl which don't have it, but that's not my problem.] > > I'm unfamiliar with how Perl_seed is supposed to work, and how such > a seed is obtained. It may still be safer to use Math::TrulyRandom, > which uses the timing of interrupts to get some real random data... Perl_seed returns some random data which can then be used to seed a random number generator. (If /dev/urandom is available, it uses that; if not, it tries to get some random data from other sources.) > I'm not sure how Perl_seed is shared, between forks and between > threads, so that might be an issue with respect to security. Likely > such a seed isn't intended for cryptographic use, but is used for > seeding the hash algorithm to prevent denial of service type > attacks. It's certainly not for cryptography, but it's the standard method of generating a seed from within perl. See List::Util::shuffle for an example of its use. Don Armstrong -- Information wants to be free to kill again. -- Red Robot http://www.dieselsweeties.com/archive.php?s=1372 http://www.donarmstrong.com http://rzlab.ucr.edu -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]
