Creating the same random numbers

Andreas Leppert wudmx at
Sat Jan 29 18:49:10 EST 2011

On Sat, Jan 29, 2011 at 07:59:34PM +0000, creslin at wrote:
> But in short answer yes, if you use the same seed the same answer
> would be generated, assuming no further entropy is used later I.e
> dependent on method employed to expand. Though then the 'randomness'
> is in the seed not the output. Its this capability which allows simple
> access control token devices to operate.
I'm not quite familiar with the number generators in the kernel. Right
now I do this to get a random number betwen min and max:

/* compute the random value within the given min and max wrt to step */
int tmp_bytes, range;

range = max - min + 1;
get_random_bytes(&tmp_bytes, sizeof(tmp_bytes));
if (0 > tmp_bytes)
	tmp_bytes = -tmp_bytes;
new_random_param->curval = tmp_bytes % range + min;

You mentioned the seed value. Is there a way to set a seed value before
I invoke get_random_bytes? Could you direct me to a page / source file
where I can get more information about it?

Thanks for all responses so long!
Andreas Leppert

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