Re: One-line password generator

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Andy Smith wrote:
> https://www.2uo.de/myths-about-urandom/#experts

So it is about how Daniel Bernstein justifies his claim that it is
wrong to say:

  "we can't figure out how to deterministically expand one 256-bit
   /dev/random output into an endless stream of unpredictable keys
   (this is what we need from urandom),"

and right to conclude:

   "For a cryptographer this doesn't even pass the laugh test."

How do cryptographers manage to get this miraculous growth of information
if the only secret is the 256 bit of /dev/random output ?

Why would i need more than 2 exp 256 tries to guess the whole stream ?


(I don't point out that this refers to /dev/random as source of
 /dev/urandom, because i assume that this is only rethorical to
 illustrate the more general question.
 Further i understand that Linux changes the key in the time range
 of minutes. This seems to be a much stronger precaution than
 just a single key.)

(And again, it's not about IT but about math. In practice 2 exp 256
 or 2 exp 384 are enormous numbers.
 Nevertheless, being sloppy in math can bite you in practice.)


Have a nice day :)

Thomas