Subject: Re: replace kernel random number function
To: None <firstname.lastname@example.org>
From: Kenjiro Cho <email@example.com>
Date: 10/23/2000 23:43:41
> >> deraadt told me that i should not replace random(9), as there can be
> >> some code depending on poorness, or uniformity, of random(9).
> >??? Can you/he point to some examples of this? Sounds a little bit
> >suspect to me...
> sys/arch/sparc/sparc/clock.c assumes that random(9) returns uniform
> random number (at least the comment says so).
> if we take a safer side, we should not replace random(9), or we should
> repalce random(9) with a random number generator with uniform
> number distribuion. i still am not really sure if it matters (i
> suspect it does not).
Traditionally, uniformity is the most important property of a
pseudo-random generator in computer science.
Also, in the Internet research, lots of new algorithms such as RED
employ probablistic behavior. The curent random() is good for them.
I believe that the algorithm was designed for the following
- its cycle should be as long as possible
- "random() % N" should be fairly uniform for any N (32bit interger)
I read the original paper a long time ago, so, I could be mistaken.
"Random number generators: good ones are hard to find",
Park and Miller, Communications of the ACM, vol. 31, no. 10,
October 1988, p. 1195.