Re: Security Considerations section for draft-fair-ipdvb-req-04.txt

[Haitham Cruickshank <H.Cruickshank@eim.surrey.ac.uk>]

Hi again,

Before answering the specific issues that Art raised, I like to say that most of
the material in my previous email (Security Considerations section for
draft-fair-ipdvb-req-04.txt) are taken from two source:

* draft-ietf-pilc-link-design-15.txt:  This document has the consensus of many
people in the IETF, where Gorry is a co-author.
* Mr. Laurent Claverotte email, where Alcatel are actively developing DVB-RCS
equipment.

See in-line for extra replies:

"Allison, Art" wrote:

> The suggestion made in the email from Haitham Cruickshank did not seem a
> reasonable one to me; but I stand ready to hear additional, relevant
> reasons.  To start, I would like to probe the reasons  that I found lacking
> in applicability a bit.. see embedded excerpts and responses.
>
> Art
> ::{)>
> Art Allison
> Director Advanced Engineering
> NAB
> 1771 N St NW
> Washington DC 20036
> 202 429 5418
>
> -----Original Message-----
> From: Haitham Cruickshank [mailto:H.Cruickshank@eim.surrey.ac.uk]
> Sent: Wednesday, March 17, 2004 6:00 AM
> To: ip-dvb@erg.abdn.ac.uk
> Subject: Security Considerations section for draft-fair-ipdvb-req-04.txt
>
> Hi All,
> <snip>
>
> However, subnetwork security is important [LINK] and should be
> encouraged, on the principle that it is better than the default
> situation, which all too often is no security at all.  Users of
> especially vulnerable subnets (such as radio/broadcast networks and /or
> shared media Internet access) often have control over at most one
> endpoint - usually a client and therefore cannot enforce the use of
> end-to-end mechanisms.
> AA> Just what is the alleged vulnerability? To what exactly?

The vulnerability refers to two separate issues:

1. Satellite and wireless links are more vulnerable to attacks such as
eavesdropping and traffic analysis due to the broadcast nature of these links.
2. End users might not have control on the overall link such as the link between
the service provider and the satellite gateway.

>
>
> A related role for subnetwork security is to protect users against
> traffic analysis, i.e., identifying the communicating parties and
> determining their communication patterns and volumes even when their
> actual contents are protected by strong end-to-end security mechanisms
> (this is important for networks such broadacst/radio, were
> eaves-dropping is easy).
> AA> Let us explore this a bit. What communication pattern? All that I can
> see is that the emission station sends x% of their packets using ULE. How is
> a traffic analysis of any kind going to harm a broadcaster in any way?
> Please describe how this a threat to the transmitter operator?
> /

Even if the information is encrypted, it is possible for intruders to identify
communicating parties identities from IP addresses (if not encrypted) or
satellite terminal MAC addresses.  Therefore intruders can identify the
satellite operator customers and this is really bad if the customer is a high
profile organization (such as UK MoD or US DoD).

>
>
> Finally an important role for subnetwork
> security is the protection of the subnetwork itself.  Possible threats
> to subnetwork assets include theft of service
>
> AA> Please explain what service is protected from being stolen by this
> addition.
> If the contents are not usable, (and each service has many means to so
> insure), what can one do with these packets?
> /

This point is really about source authentication to prevent intruders from high
jacking a satellite link and pretending to be a legitimate user.

>
>
> and denial of service;
> shared media subnets tend to be especially vulnerable to such attacks
> AA>I don't see this in the RF domain.

Yes I agree it is difficult in the RF domain

> One way to deny service from a DTV
> transmitter is to create interfering RF energy that prevents reception.
> While possible, RF DFing works fine to track down and eliminate the attacker
> were it to occur- and it wipes out all reception, not just some packets. I
> fail to see a motive for anyone to make such an investment, the cost of
> which is directly related to the number of receivers interfered with. For a
> satellite service it is much harder to interrupt as one must get into the
> aperture of the antenna.
>
> But you posit a even more complex and sophisticated attack... here is what I
> think would be required to do selective denial of service at the MPEG packet
> level:
> One would have to demodulate the stream, then strip <just> the packets that
> contain the service to be denied, the re-emit the altered stream (replacing
> the deleted packets with null or faked packets) and recreate the RF
> modulation. And even then the attacker would only affect those where he
> could achieve local undesired to desired signal levels (as he has to
> override the desired stream with his undesired stream).
> /
>

Yes agree.

>
> Security concerns not just the packet data being communicated, but also
> the control protocols.
> AA> Please explain how the control protocols could be altered in the real
> word considering the RF systems.
> /
>

This is a system issues not RF. Control protocol refer to two areas:
* Connection establishment/termination messages
* Network management and routing messages.

If intruders can send bogus control/routing messages, then legitimate users
might experience denial of service attacks.


>
> Appropriate security functions must therefore be
> provided for ipdvb support protocols [LINK].
>
> AA> Please provide additional information to show what risk is mitigated in
> order to support your assertion that this 'must' be done. So far you have
> not enabled me to see any concrete basis for this complexity, nor that there
> is even a very small real attack risk.

It is interesting to see that you have such optimistic views about security
relating issues, where companies such as CANAL+   have paid a heavy price for
smart card frauds (DVB-S Conditional Access).

Haitham

>
>
> Art
> ::{)>
> Art Allison
> Director Advanced Engineering
> NAB
> 1771 N St NW
> Washington DC 20036
> 202 429 5418

--
Dr. Haitham S. Cruickshank

Senior Research Fellow
Communications Centre for Communication Systems Research (CCSR)
School of Electronics, Computing and Mathematics
University of Surrey, Guildford, Surrey GU2 7XH, UK

Tel: +44 1483 686007 (indirect 689844)
Fax: +44 1483 686011
e-mail: H.Cruickshank@surrey.ac.uk
http://www.ee.surrey.ac.uk/Personal/H.Cruickshank/