[cryptography] urandom vs random

ianG iang at iang.org
Sat Aug 17 06:01:39 EDT 2013

On 17/08/13 10:57 AM, Peter Gutmann wrote:
> Nico Williams <nico at cryptonector.com> writes:
>> It might be useful to think of what a good API would be.
> The problem isn't the API, it's the fact that you've got two mutually
> exclusive requirements, the security geeks want the (P)RNG to block until
> enough entropy is available, everyone else wants execution to continue without
> being blocked.  In other words a failure of security is preferred to a failure
> of functionality.  Until you resolve that conflict, no API (re)design is going
> to help you.

(not answering the posts sepcifically but) the rule of thumb I've always 
used is this:

If you don't care so much about security then use the tools that are 
provided, and suffer an occasional glitch.  Don't worry too much about 
the glitches coz your business already told you, you don't care too much 
about the security / randomness.  All those cypherpunkian arguments can 
go to hell, you've got customers to care for.

OTOH, if you care a lot, then you have to write your own.  The design is 
now very well established.  Many sources -> mixer/pool -> deterministic 
PRNG.  It's really not that hard, this is an intern level project, folks.

In result, if you care enough to argue about random v. urandom then you 
already put yourself in the second camp, and your problem is solved. 
Just use urandom and collect some other sources yourself.  You no longer 


More information about the cryptography mailing list