[87778] in Cypherpunks
Re: Secure phone
daemon@ATHENA.MIT.EDU (Eric Blossom)
Mon Oct 6 16:37:39 1997
Date: Mon, 6 Oct 1997 12:17:25 -0700
From: Eric Blossom <eb@comsec.com>
To: aba@dcs.ex.ac.uk
Cc: frantz@netcom.com, cypherpunks@Algebra.COM
In-Reply-To: <199710061757.SAA01293@server.test.net> (message from Adam Back on Mon, 6 Oct 1997 18:57:44 +0100)
Reply-To: Eric Blossom <eb@comsec.com>
> Bill Frantz <frantz@netcom.com> writes:
> > At 6:25 PM -0700 10/5/97, Adam Back wrote:
> > >On the other hand, using persistent key public key crypto, Tim has
> > >been signing his posts recently, and I have an ancient public key of
> > >his stashed away which his new key is signed with. If we were able to
> > >construct a protocol to bolt on top of the reading of hashes, we could
> > >have much greater protection against MITM.
> >
> > Of course if you can use PGP as well as the secure phone, you can use PGP
> > to exchange a pad of one-time passwords.
>
> The passwords alone don't do you any good: if you read them out over
> the phone, Eve can just repeat them.
There's no reason you couldn't use the passwords in a bidirectional
challenge/response scenario. The units can pass (optionally
encrypted) control messages back and forth while in secure voice mode.
Eric
