From: Timothy A. Ryan <gymnast@Crissy.Stanford.EDU>
Date: Sat, 12 Feb 94 18:11:10 PST
To: Jim_Miller@bilbo.suite.com
Subject: Re: a protocol
In-Reply-To: <9402130044.AA01412@bilbo.suite.com>
Message-ID: <9402130204.AA03480@Crissy.Stanford.EDU>
MIME-Version: 1.0
Content-Type: text/plain


> 
> 
> An idea came to me today for a protocol for exchanging keys  
> point-to-point (inspired by the Robert Cain messages).  The protocol  
> is a just combination of the Interlock Protocol described on page 44  
> of "Applied Cryptography" and Diffie-Hellman, describe on page 275.
> 
> Keeping with the terminology of the book, Alice will attempt to  
> exchange a key with Bob, and Mallet will attempt to sit in the middle  
> without being detected.
> 
> As has been demonstrated in the past, I haven't read a lot of the  
> cryptography papers that are out there, so for all I know, this is a  
> well known protocol (or simple variation).  However, I haven't seen  
> it, and it seems interesting.  Anyways, on with the show...
> 
> 
> 1) Alice sends Bob her public key.  (ala Interlock Protocol)
> 
> 2) Bob sends Alice his public key.
> 
	:
	:
	:

> Jim_Miller@suite.com
> 
> 

	Could someone briefly explain the Interlock Protocol, I don't
have "Applied Cryptography".  However, it seems that Jim's protocol
depends on the Interlock Protocol guaranteeing that Alice really
gets Bob's public key and vice versa.  Otherwise, it seems that
Mallet could give each of Alice and Bob his (or is that a feminine
name?) public key, go through Jim's protocol with each party, then
just translate every message from cipher-text to clear-text then
back to cipher-text using the key for the other half of the conversation.

	tim