Re: pre-shared key v RSA encryption or RSA signature authentication modes

[Derek Atkins <warlord@mit.edu>]

Yes, the low entropy of shared secrets is due to the fact
that most of them are derived from short or weak passwords.
If you have a 128-256 bit random key for a shared secret, you
have the problem of transmitting that secret confidentially
between the hosts.  If you use RSA, then all you need is
integrity across the distribution channel.

-derek

David Jablon <dpj@theworld.com> writes:

> Derek,
> 
> Is the limited entropy of the shared secret due to the fact that
> it is simply a hash of a password?  If so, then perhaps the current
> simplistic shared-secret key protocol is not such a good fit for these
> common shared-secret password applications.
> 
> -- David
> 
> At 11:39 AM 3/21/2002 -0500, Derek Atkins wrote:
> >The fact that most users wont have a shared secret with 256 bits of
> >entropy?  I suspect that most shared secrets are probably in the 64-80
> >bits of entropy at the highest, and probably much lower than that.
> 
> 

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord@MIT.EDU                        PGP key available