Subject: [SIP] SIP gateways and authentication

From: "James A. Donald" <[email-masked]>
Date: Sun, 03 Sep 2000 20:00:51 -0700

--
James A. Donald writes:
 > > In all public key solutions,the public keys are used to set up a
 > > symmetric key that is not subject to dictionary attacks.

At 09:32 AM 9/1/2000 -0700, Michael Thomas wrote:
 > False. A public key solution that chose bad  symmetric keys would be
 > subject to dictionary attacks and much more.

All existing public key protocols, for example https, generate ephemeral 
computer generated symmetric keys that are invulnerable to dictionary attack.

The SPEKE protocol, the various EKE protocols and the PGP phone protocol 
also generate ephemeral computer generated private keys that are 
invulnerable to dictionary attack, as well as generating ephemeral computer 
generated symmetric keys that are invulnerable to dictionary attack.

James A. Donald:
  > > Existing symmetric key solutions (Kerberos) are vulnerable to
  > > dictionary attack

Michael Thomas
 > This is a ludicrous strawman.

This is a simple fact, as has been proven by experiment.  Once again, I 
point you to http://theory.stanford.edu/~tjw/krbpass.html

 >  People choose dictionary attackable symmetric keys, not Kerberos.

People will always choose such passphrases.  Kerberos allows the 
attack.  Modern systems do not.

Modern systems, such as SPEKE, are secure even when people choose such 
passwords, as they almost always do.

     --digsig
          James A. Donald
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      UP7kKPgsDeT0+7xcZCaBx+MpR1w99cX8FWDKmH3Z
      4/komD2VbLq1nRMs2vSomlGd1IBRC+OkbOsQGFW6x

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