Re: [boost] GUIDs

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-07-03 17:37:44

Sean Parent wrote:

> If you know of a good library for cryptographic quality random
> numbers I'm interested - that's the core issue right now for the ZUID
> library is ensuring enough entropy for the node ID.

I don't know of a portable library for obtaining entropy; I'd expect 
/dev/urandom to be one on POSIX OSes but its quality would probably vary. 
For Windows XP, there is RtlGenRandom:

http://windowssdk.msdn.microsoft.com/en-us/library/ms732683.aspx

and the algorithm behind it is explained in:

http://blogs.msdn.com/michael_howard/archive/2005/01/14/353379.aspx

For GUIDs, one would typically obtain "a sufficient amount" of entropy only 
once at startup and use it as a seed for a high quality PRNG, so speed 
shouldn't be an issue. I haven't needed a portable PRNG implementation so 
far (usually I also need other crypto facilities and use whatever the crypto 
library provides) so I'm not sure whether a de-facto standard has emerged as 
is the case with encryption (AES) and hash functions (SHA2).