Does shuffle() produce uniform result ?

[Antoon Pardon]

On 2007-09-03, Paul Rubin <http> wrote:
> Antoon Pardon <apardon at forel.vub.ac.be> writes:
>> If I understand correctly that you are using urandom as a random
>> generator I wouldn't trust too much on this performance. Urandom
>> uses the systemwide entropy-pool. If other programs need this pool
>> too, your performance can drop spectaculary. 
>
> No the idea is that once there's enough entropy in the pool to make
> one encryption key (say 128 bits), the output of /dev/urandom is
> computationally indistinguishable from random output no matter how
> much data you read from it.

If you were talking about /dev/random I would agree. But this is what
the man page on my system says about /dev/urandom

       A read from the /dev/urandom device will not block waiting for
       more entropy.  As a result,  if  there  is  not  sufficient
       entropy  in the entropy pool, the returned values are
       theoretically vulnerable to a cryptographic attack on the algorithms
       used by the driver.  Knowledge of how to do this is not available
       in the current non-classified literature, but it is the-
       oretically possible that such an attack may exist.  If this is a
       concern in your application, use /dev/random instead.

And reading from /dev/random can block if there is not enough entropy.

-- 
Antoon Pardon