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AW: Réf. : Re: Encryption control of SNDU
> -----Ursprüngliche Nachricht-----
> Von: owner-ip-dvb@erg.abdn.ac.uk
> [mailto:owner-ip-dvb@erg.abdn.ac.uk] Im Auftrag von
> Tarif.Zein-Alabedeen@space.alcatel.fr
> Gesendet: Donnerstag, 26. Februar 2004 17:23
> An: ip-dvb@erg.abdn.ac.uk
> Betreff: Réf. : Re: Encryption control of SNDU
> Wichtigkeit: Niedrig
>
>
>
>
> Hi alain and every body
> Concerning point I, let me go back to dvb-rcs : encryption at
> the encapsulation layer (which is now MPE but may become ULE
> in the future) has been provisioned and the way it is
> controlled by the 2 bits field in the MPE header has been
> clearly specified (see my precedent mail)
>
> I am not aware of the exact reasons which led poeple who
> contributed to the dvb-rcs definition to do this may be they
> did something wrong or expected a functionnality that will
> never be used....!!!! But it is more probable that they had
> real reasons to do this (so we can avoid to reinvent the
> wheel as you said) Any one has an idea?
Before requiring the adoption of these 2bits we really should know and understand their reasons, and assess if they still exist for ULE.
>
> I see an example which could make case 3 difficult to apply.
> It concerns bridging When forwarding (in the Gateway for
> example) is performed by bridging (as in Ethernet switches)
> and not by routing (as routers), IPsec can not apply because
> the GW handles frames and not datagrams (am I wrong?). Such
> case may happen with e.g a PPPOE access scheme. So if IPsec
> is not applied end-to-end (but this can not be controlled by
> the satellite segment), traffic will be transmitted clear on
> the sat interface
I don't think your example above necessarily means cleartext transmission.
Even when briding is used on the encapsulator, there is a node before, which performs routing functionality. Often this node is controlled by the same entity as the encapsulator in "bridging mode" (e.g. a Teleport operator), so the IPsec SA could start in this case on the router.
In case the encapsulator in "bridging mode" and its closest preceding router are controlled by different entities, you still could apply security on MPEG level.
Cheers,
Wolfgang
>
> Concerning the use of the extension header, the main question
> is : when encryption is applied at ULE level, do we need the
> encryption control field in all SNDUs or not. If yes, the
> extension header solution may turn to be inefficient since it
> would lead to about 5 bytes extra header (taking your example
> below). I submitted this question to Alcatel's security
> experts but would be great if others in this groupe could
> also think about it and make suggestions
>
> regards
>
>
>
>
>
> Alain RITOUX <alain.ritoux@6wind.com>@erg.abdn.ac.uk on
> 26/02/2004 15:25:15
>
> Veuillez répondre à ip-dvb@erg.abdn.ac.uk
>
> Envoyé par : owner-ip-dvb@erg.abdn.ac.uk
>
>
> Pour : IPDVB <ip-dvb@erg.abdn.ac.uk>
> cc :
> Objet : Re: Encryption control of SNDU
>
>
>
>
> Gorry Fairhurst wrote:
>
> > So, I'm trying to build a list of "issues for ULE" and the
> questions I
> have
> > are:
> >
> > (i) Does the proposed ULE base header format (4/12B of
> header) need to
> > be changed to support any required encryption/scrambling?
> >
> > Possible answers include:
> >
> > * Yes - because the ULE header must not be increased when
> > link encryption is used.
> >
> > * No - because the ULE header can specify a TYPE that could
> > indicate an encrypted payload, and hence this issue
> > could be solved by using an extension header of some form.
> >
> > If it is YES, then this has design implications for the ULE Spec.
>
> I would say No, because :
> - I don't really understand the need for ULE level encryption
> see point I)
> - If needed, it can be separated from ULE base specs. see point II)
>
> I) Why ULE level encryption ?
> =============================
> I still don't sse the need for an ULE-level encryption,
> because I see 3 possibilities of encryption
> 1) At MPEG-2 level, i.e. same encryption for whole content of a PID
> 2) At ULE level, i.e. encryption on a per SNDU basis for the case as
> Tarif said, where PID is mutli-receiver (belonging to
> different groups)
> 3) At IP level
>
> but what can distinguish 2 SNDU ?
> - IP addresses ?
> - DVB Mac addr ?
> But the DVB Mac addr is itself the result of IP
> address/prefix resolution (which can use destination and/or
> sources) So I think it can all be expresed in term of either
> destination and/or source Addresses, which can perfectly be
> handled by IPsec. So 2) and 3) seem to me to offer the same
> granularity and 3) is already defined and working.
>
> This is my current understanding, and a counter-example
> where 2) would solve a use-case and not 3) would be very
> helpfull. Anyway, I may have missed something, so :
>
> II) Etxension Header for Encryption
> ====================================
> *IF* an ULE encryption is needed, then some extension header
> can be defined to provide it, so the SNDU would be like :
>
> - [ULE_Header] [DVB_MAC*] [SEC_Header] [xxx SNDU Payload xxx]
> |
> +--> Type = sec_header
> (*) if MAC addres bit is '0'
>
>
> - The SEC_Header would be
> +---+---+---+--// ..... // ----+
> | NH | L | security params |
> +---+---+---+--// ..... // ----+
>
> with NH = Type of SNDU payload (IP, IPv6, ...)
> L = Length of SEC_Header
>
> security params will define key material, type of security
> (encryption, authentication, ....), algo, whatever ...
>
> In the extension headers I proposed, the SEC_Header would be one
> of the "drop packets if unknown" type.
>
> - The SNDU payload woul be clear/encrypt/padded accordingly to what
> params will be found in SEC_Header.
>
> With that approach, the only thing needed is to include the
> Extension Headers mechanism definition in the ULE base specs.
> Then ALL that SEC_Header stuff can be described in a separate
> doc, and good luck with the (re)keying framework/protocols,
> security analysis ...
>
> Regards.
> Alain.
> --
> Alain RITOUX
> Tel +33-1-39-30-92-32
> Fax +33-1-39-30-92-11
> visit our web http://www.6wind.com
>
>
>
>
>
>
> T. Zein
>
> ALCATEL SPACE
> DRT/RST -- Ingénieur Systèmes
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