using /dev/random

[Lowell Gilbert]

Robert Huff <roberthuff at rcn.com> writes:

> 	What is the canonical way to get data from /dev/random?
> Specifically: having opened the file, how do I read the stream?
> I'm currently using
>
>
>   union {
>     float f;
>     char c[4];
>   } foo;
>
>   foo.f = 0.0;
>
>   fscanf(rand_fp,"%4c",foo.c);
>
>
> 	which doesn't seem to produce anywhere near "random bytes" as
> promised by the man page.

Have you turned off the "seeded" variable?  You'll fall back to a
software pseudorandom sequence if you don't.

Most computers don't have all that much real random data ("entropy") to
work with, and if you need a lot of random data, you're more or less
forced to use a good pseudorandom generator.  "Good" can vary a bit
depending on application, but random(3) is generally more than good
enough for monte carlo style simulation purposes.

Cryptography is another story.  I have a hardware random number
generator on my server, which helps with performance in some cases...


-- 
Lowell Gilbert, embedded/networking software engineer, Boston area
		http://be-well.ilk.org/~lowell/