Re: A Key Exchange Puzzle for sci.crypt readers

From: lyal (lyalc_at_spam.ozemail.com.au)
Date: 12/08/03 

Date: Mon, 8 Dec 2003 19:29:22 +1100

"Paul Rubin" <http://phr.cx@NOSPAM.invalid> wrote in message
news:7xllpng6ub.fsf@ruckus.brouhaha.com...
> jsavard@ecn.aSBLOKb.caNADA.invalid (John Savard) writes:
> > A and B wish to communicate securely.
> >
> > Anyways, they share a secret key-exchange key which consists of a
> > simple substitution table with 256 entries.
>
> If they have a shared secret key, they can use a normal secret-key
> protocol. What's the purpose of your crazy one?

There are many environments where the bandwidth and CPU involved with
symmetric key exchanges are to expensive.

Generating a message unique key that is easily recoverable by the entity
holding the same master key as the sender is much easier than the 3 or 4
pass symmetric protocols, and enormously faster and more efficient than
public key in our experience.

Saving 5k bytes of cert size of a 9600 bps link (e.g. mobile phones) has a
huge payoff in network and useability benefits.

Lyal

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