Nmap Development: Re: Performance thoughts

[Diman Todorov <diman () xover mud at>]

> Interesting.  We assumed that the OpenSSL random number generator
> would be better and so we use that if it is available.  But it sounds
> like it isn't as efficient as using Linux's /dev/urandom .  I'll
> remove that (openssh random number) functionality for ALPHA3.
>
> o Nmap no longer gets random numbers from OpenSSL when it is available
>   because that turned out to be slower than Nmap's other methods
>   (e.g. /dev/urandom on Linux, /dev/arandom on OpenBSD, etc.).  Thanks
>   to Marek Majkowski for reporting the problem.
Yes /dev/urandom should perform better but it is not really random.
I have run into problems with it's short period before.
A look at the mersenne twister at http://www.math.sci.hiroshima- 
u.ac.jp/~m-mat/MT/emt.html
might be a good idea. They provide c code for the random number
generator although I don't know how well it performs compared
to openssl and /dev/urandom
I have used their code to draw random samples of 5k from datasets of  
10bio samples
which worked ok.

cheers
Diman


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