From: paul@fatmans.demon.co.uk
Date: Sat, 5 Oct 1996 07:09:46 +0800
To: cypherpunks@toad.com
Subject: Re: DESCrack keyspace partitioning
Message-ID: <844458782.11259.0@fatmans.demon.co.uk>
MIME-Version: 1.0
Content-Type: text/plain



> Seems to me that a _subset_ of all possible keys is much more likely
> to appear than a random selection from an equidistributed population 0..2^56.

No, this is not true of a good PRNG

> (P)RNG's just aren't that likely to produce a key of 010101010.....
> nor 001100110011... etc etc and I have been thinking about how one might formalize 
> and exploit this randomness property to increase the probability of finding the key sooner.

Good PRNGs are as likely to produce these key values as anything 
else. the reason random looking patterns occur more often is because 
there are more of them.


> Is not the lack of predictability a predictable, and therefore exploitable, attribute?

The fact is a PRNG may *LOOK* predictable, ie. 111000111000 but the 
next bit will have an equal probability of being a 0 as a 1.

> Any thoughts here?

None whatsoever.
 

  Datacomms Technologies web authoring and data security
       Paul Bradley, Paul@fatmans.demon.co.uk
  Paul@crypto.uk.eu.org, Paul@cryptography.uk.eu.org    
       Http://www.cryptography.home.ml.org/
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     "Don`t forget to mount a scratch monkey"