Subject: [ippm] Re: owamp protocol

From: stanislav shalunov <[email-masked]>
Date: 29 Jun 2004 18:45:51 -0400

[[email-masked] added to CC]

Roman Lapacz <[email-masked]> writes:

> very soon I will deploy OWAMP implementation in PSNC (there was the
> discussion about this with Eric Boyd during Terena 2004 Conference) but
> before that I would like to have a solid knowledge about OWAMP protocol
> (and furthermore its implementation on the C code level).
> 
> I've read the draft of the protocol and I have few questions. First, the
> process of establishing an encrypted and authenticated connection is
> rather unclear for me. I know MD5 and AES, what is for and how it works
> generally, but according to the draft I can't understand exactly the use
> (step-by-step) of Username, Token and Client-IV fields.

Roman,

I presume you're talking about the instructions in section 5.1 of
draft-ietf-ippm-owdp-08.txt.  Which part do you have difficulty
interpreting?

It would be helpful if you asked more specific questions.

Username is a string, 16-octet long, used to refer to a particular
shared secret.  The server might be prepared to conduct encrypted
sessions with more than one client.  The Username tells the server
which key to use.

Token is described in the paragraph starting with ``Otherwise,
[...]''.  It is necessary to know what Cipher Block Chaining means.
This has the standard meaning, i.e., the plain text of second block is
XORed with the cipher text of the first block before the former is
encrypted.

It might help to take a look at a cryptography book to refresh the
terminology.  For example, the _Handbook of Applied Cryptography_ is
immediately available for free in electronic format at
http://www.cacr.math.uwaterloo.ca/hac/, but Bruce Schneier's _Applied
Cryptography_ might be a better source.

If you have more specific questions, please do not hesitate to ask
them: if you have difficulty understanding something, there will be,
no doubt, someone else with the same difficulty.  But to make the text
better and more understandable, it must be known what is the exact
part that causes problems.

-- 
Stanislav Shalunov		http://www.internet2.edu/~shalunov/

Sex is the mathematics urge sublimated.                 -- M. C. Reed.

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From: Roman Lapacz <[email-masked]>
Date: Wed, 30 Jun 2004 13:15:36 +0200

> sessions with more than one client.  The Username tells the server

Stanislav,

finally, I understand section 5.1 (it took me a while :). I think (maybe
I'm wrong) there should be exact information in the text that there are
the same bindings 'username-secret_key' stored on both sides (client ad
server) before the protocol starts. Maybe this could clarify the
description of secured session establishing.

Roman