building a true RNG

[John S. Denker]

David Wagner <daw at cs.berkeley.edu> writes:
>>> I don't know of any good cryptographic hash function 
>>> that comes with a proof that all outputs are possible.  

What about the scheme
	Pad -> Encipher -> Contract
described at
  http://www.monmouth.com/~jsd/turbid/paper/turbid.htm#sec-uniform-hash

>>> if we apply the Luby-Rackoff construction 
>>> (i.e., 3 rounds of a Feistel cipher), with
>>> ideal hash functions in each round, does this have 
>>> the desired properties? It might.

Paul Crowley wrote:
> >
> > This seems to define a block cipher with no key, which is collision
> > free but not one-way.  Am I misunderstanding what you're proposing?

David Wagner wrote:
> 
> You understood it perfectly.  Good point.
> I didn't notice that problem.  Harrumph.

There is only the most minor of problems here, namely
that DAW mentioned a symmetric cipher.  The problem goes 
away if you use asymmetric crypto.  You want a cipher with
no _deciphering_ key, as described in my paper.  (op. cit.)

---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at wasabisystems.com