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RE: On shared keys (was RE: SOI: identity protection and DOS)

Alex,

With all due respect, I think the ATM network is a great example of why PSK (symmetric kind) security is an expensive and non scalable solution.

First of all, the banks do take security seriously and implement the DES security for ATM's the way we suggest for PSK, but no-body does.

Every ATM is loaded with x months of DES keys by two security guards. Each guard holds one half of a master key that is used to unlock the sets of keys to be loaded into the ATM. You call this a simple and scalable solution? I don't think so. It's expensive as heck, but fortunately for the banks, we get to foot the bill.

And I disagree that internet hosts are an order of magnitude smaller in deployment.

Consider the current situation with SSL-based web transactions. If you consider the number of endpoints, both servers and browsers, participating in a trusted, secured transaction I think you'll find that those numbers are vastly larger than the number of ATMs in the world. The certificate-based trust model is far easier and much more managable to deploy than any shared secret scheme. (I'd sure consider it expensive to have two burly security guards show up at my front door to load 4 months of DES keys into my browser)

Personally, I'd like to see the end of all PSK in IPSec and go to a certificate-based PK trust model. Which is why I really liked the JFK proposal. To those that would like raw public keys, I say this. It's not hard to wrap a PK in a self-signed certificate and it buys you a lot. Moving up to a CA chain buys you that much more.

And finally, as for the compromises of credit card numbers and the like... Not one of those was due to a flaw in security protocols. They were a result of implementation errors in applications. Unfortunately (or maybe fortunately) IPSec does not take on that responsibility.

Lee Dilkie

Mitel Networks
350 Legget Drive
Kanata, ON, Canada
K2K 2W7

Phone: 1-613-592-5660

"It wasn't easy to juggle a pregnant wife and a troubled child, but somehow I managed to fit in eight hours of TV a day."
     - Homer Simpson (from "The Simpsons")


> -----Original Message-----
> From: Alex Alten [mailto:Alten@home.com]
> Sent: Wednesday, November 28, 2001 3:54 PM
> To: andrew.krywaniuk@alcatel.com; 'IPsec WG'
> Subject: RE: On shared keys (was RE: SOI: identity protection and DOS)
> 
> 
> 
> You have completely missed my point, and incorrectly lumped 
> Visa and ATM
> security systems together.
> 
> My point is that for over 20 years hundred's of millions of 
> people have
> been using *DES* to get cash out of ATM machines.  This is a 
> very large 
> scale system, the number of Internet hosts is an order of 
> magnitude smaller.
> As far as I know there has never been a major compromise of 
> this system,
> where lots of money was stolen from thousands of accounts.
> 
> - Alex
> 
> 
> At 08:58 PM 11/27/2001 -0500, Andrew Krywaniuk wrote:
> >Your argument is silly.
> >
> >Visa and ATM transactions aren't secure. There are multiple 
> cases where
> >large credit card databases have been compromised (often 
> when an online
> >merchant's website is hacked). 
> ...
> >
> >
> >> -----Original Message-----
> >> From: owner-ipsec@lists.tislabs.com
> >> [mailto:owner-ipsec@lists.tislabs.com]On Behalf Of Alex Alten
> >> Sent: Tuesday, November 27, 2001 12:24 PM
> >> To: Hugo Krawczyk; IPsec WG
> >> Subject: Re: On shared keys (was RE: SOI: identity 
> protection and DOS)
> >>
> >>
> >> At 01:34 AM 11/27/2001 +0200, Hugo Krawczyk wrote:
> >> >Everyone agrees that public key is the ONLY way to a scalable
> >> >Internet-wide protocol. No question about it. In particular,
> >> >any key-exchange protocol for IPsec MUST provide a 
> PK-based exchange.
> >> >
> >>
> >> No.  I STRONGLY disagree.  I'll give a counter example.  
> The banking
> >> ATM network uses DES keys.  It has scaled, in practice, world wide.
> >>
> >> And BTW, it's security & trust model is excellent.  Have you
> >> ever heard
> >> of a major compromise, say on the scale of 25,000 card #'s
> >> being stolen
> >> (like with Visa?).  Certainly nobody distrusts it because it uses
> >> symmetric keys for authentication.  In fact I'm certain 
> YOU trust it
> >> at least a couple a times a month.  :-)
> >>
> 
> --
> 
> Alex Alten
> Alten@Home.Com
>
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