Subject: RE: [MSEC] new TESLA draft

From: LANIEPCE Sylvie FTRD/DMI/CAE <[email-masked]>
Date: Fri, 5 Apr 2002 17:12:31 +0200

Hi,

Regarding Ran's TESLA layer placement question, here are some
comments/questions (debate welcome):

I was wondering about the relevance of a msec gateway. Basically, the msec
gateway would operate as a boundary between an unsecured network (where the
data coming from the source are protected by msec) and a safe network (an
intranet for example, where fewer security protections are needed). Note
that this scenario could be efficient in terms of key management, as the
gateway could act in replacement of many receivers located within the safe
network.
So, in this case where data security treatments are externalized from the
receivers, within a gateway, it seems to me that it would be better, for
performance and cost reasons, to provide these security treatments at IP
layer, instead of crossing all the gateway TCP/IP stack up to the
application layer.

I have the feeling (not that easy to demonstrate) that performing MSec
treatments at IP layer is efficient if you opt for possibly externalized
(from members, both sender and receiver) msec functionalities . This
question probably goes with the relevance of outsourced msec functionalities
(data treatment and also key management).

On the source side, could msec perform some sort of traffic analysis
protection (hiding source IP@ ?) if implemented at IP layer ?

Are there any cases where application layer placement could give access to
selectors not available at other lower layers, in order to apply different
security treatments to different types of data within a given application ? 

Would TESLA be one source authentication solution among others for
MESP/AMESP or would MESP/AMESP stick to TESLA ?

Ran, I do not clearly understand why you mention a TCP hypothesis, since
multicast goes with UDP. See TESLA draft, section 5 (drawbacks attached to
TCP delays) ?

I am not especially pushing hard IP layer placement, I am just letting you
know what I can think about (and my analysis is probably (too much)
influenced by the IPSec model, altought any AESP...). I am interested in
considering, understanding and analyzing any argument in favour of an
application layer placement.

In addition, I am keen to look at msec also considering in details :
- the security services msec can provide in real applications
- the opportunities for an ISP to provide msec related functionalities
in order to take into account their impacts (if any) on msec design. Any
opinion on that subject ?

Hope this helps 

Regards
Sylvie
France Telecom R&D - DMI/SIR

-----Message d'origine-----
De : Ran Canetti [mailto:[email-masked]]
Envoye : samedi 2 mars 2002 16:08
A : [email-masked]
Objet : [MSEC] new TESLA draft

[Co-chair hat off]

Folks,

Please take a look at the following new I-D:

http://search.ietf.org/internet-drafts/draft-perrig-msec-tesla-intro-00.txt

It provides a general algorithmic/informational presentation of the TESLA
source authentication mechanism. (This is an updated version of the
irtf-smug draft from a year ago.)

While you read, please keep in mind the following issue. Our planned next
step is to write a standards-track draft describing how to implement
TESLA in a specific scenario. The question is: how to go about it?
In particular, should we first implement TESLA in the application layer
or in the IP layer? There are advantages to each option (they are discussed
in the draft). We would like to get the WG feedback on the draft in general
and on this question in particular.

Thanks,

Ran

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