🚀 go-pugleaf

"Clemens" <metax@despammed.com> writes:

> dd if=urandom of=/dev/hdb
> dd if=random of=/dev/hdb
> 
> I want to overwrite my harddisk with random gibberish.
> What are the effects if I use "urandom"?
> What are the effects if I use "random"?
> 
> What would you adwise, what�s more reliable and secure?
> 

Here is the extract from urandom(4) man page on my Debian Linux:

       When read, the /dev/random device will only return  random
       bytes  within the estimated number of bits of noise in the
       entropy pool.  /dev/random should  be  suitable  for  uses
       that  need  very  high quality randomness such as one-time
       pad or key generation.  When the entropy  pool  is  empty,
       reads  to /dev/random will block until additional environ�
       mental noise is gathered.

       When read, /dev/urandom device will return as  many  bytes
       as are requested.  As a result, if there is not sufficient
       entropy in the entropy pool, the returned values are theo�
       retically  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 liter�
       ature, but it  is  theoretically  possible  that  such  an
       attack  may  exist.  If this is a concern in your applica�
       tion, use /dev/random instead.


In other words, /dev/random is more secure but much slower and will most
certainly block when large number of data is required (I think somebody
posted that he needed 10 minutes with /dev/random for the same amount of
data that  /dev/urandom could generated within 10sec).

Now, both of these might be an overkill for you.

HTH, Dragan

-- 
Dragan Cvetkovic, 

To be or not to be is true. G. Boole      No it isn't.  L. E. J. Brouwer