[cryptography] urandom vs random

James A. Donald jamesd at echeque.com
Sat Aug 17 00:02:46 EDT 2013


On Fri, Aug 16, 2013 at 10:01 PM, James A. Donald <jamesd at echeque.com> 
wrote:
>> If /dev/urandom seeded at startup, and then seeded no further, bad, but not
>> very bad.
>>
>> If /dev/urandom seeded at startup from /dev/random, then should block at
>> startup.
>>
>> If /dev/urandom never blocks, bad.  Should block at startup waiting to
>> receive 160 bits from /dev/random, and never block again.

On 2013-08-17 12:33 PM, shawn wilson wrote:
> I don't follow this - I understand why lack of entropy should block
> urandom but, why shouldn't it block on a running system that
> <low_bound?

Once  /dev/urandom has 160bits of true randomness, can generate 
cryptographically strong pseudo randomness for an unenumerably long time.


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