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Date: Wed, 12 Mar 2003 12:54:40 -0800
From: Greg Stein <gstein@lyra.org>
To: dev@apr.apache.org
Subject: Re: apr_generate_random_bytes() blocks forever
Message-ID: <20030312125440.B24764@lyra.org>
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 from ben@algroup.co.uk on Wed, Mar 12, 2003 at 08:23:21PM +0000

On Wed, Mar 12, 2003 at 08:23:21PM +0000, Ben Laurie wrote:
> Karl Fogel wrote:
> > Branko Cibej <brane@xbc.nu> writes:
> > 
> >>>Or gstein has suggested that apr_generate_random_bytes() can grow a
> >>>new flag, indicating urandom is preferred.

Actually, when we were talking, I was thinking flags to define its behavior,
more like what Ben is talking about below. For example, a flag to say
"pseudo random data is acceptable". Certainly nothing as low-level as "don't
block". The flag would indicate the *type* of data to return.

>...
> Woah! That's so wrong! The problem is that if you really want n bits of 
> _real_ randomness, you may _have_ to block.

Right.

>...
> The most general fix I can think of is an interface where you pass 
> _three_ numbers. k, n and i, where k is the number of bits of randomness 
> you want, n is the number of bits of entropy you want for _this_ chunk 
> of randomness, and i is the number of initial bits of entropy you want 
> invested in randomness.

Would n==i==0 be a typical pseudo-random generator?

Assuming so, then I like this interface. I'll also note that the UUID
generation would simply ask for k=48, n=i=0. (6 bytes of "good" random data,
but cryptographic randomness is not important)

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/