Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Re: How likely is rand() to repeat?

by jettero (Monsignor)
on Mar 08, 2012 at 20:59 UTC ( #958535=note: print w/ replies, xml ) Need Help??


in reply to How likely is rand() to repeat?

I think that's a binomial problem beyond that, it really depends on where your random numbers are coming from. Modern OSes have csrngs in them and, I suppose a few shitty bits of entropy from your mouse movements, if that works at all. Does yours? Does your CPU have one of those weird intel dual-frequency hrngs? Mine has a dedicated entropy generator, but crypto nerds are quick to point out you don't need them if you have a good csrng, just a couple good seed bits and you're fine.

I'd expect what you have to repeat eventually. Use a hash, say Digest::SHA1, and I'd expect that to be pretty damn random. Feed it the time, a rand() number, and some sequential number. I'd expect that to have a lot more bits of doesn't-repeat than your method, if only because 25 bytes isn't very many when I have databases with a few hundred thousand payment records in them. Ya know?


Comment on Re: How likely is rand() to repeat?

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://958535]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others imbibing at the Monastery: (10)
As of 2015-07-07 10:58 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (88 votes), past polls