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

If what you say is true, then the current shared-secret protocol for
IKE seems like a very bad mismatch for applications that require
use of shared-secret passwords or other man-handled keying material.

-- David

At 12:19 PM 3/21/2002 -0500, Derek Atkins wrote: 
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@xxxxxxxxxxxx> 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@xxxxxxx                        PGP key available