On Tuesday 31 May 2005 02:17, Steven M. Bellovin wrote:
In message <427CCA9B.29132.760A1FC@localhost>, "James A. Donald" writes:
-- PKI was designed to defeat man in the middle attacks based on network sniffing, or DNS hijacking, which turned out to be less of a threat than expected.
First, you mean "the Web PKI", not PKI in general.
The next part of this is circular reasoning. We don't see network sniffing for credit card numbers *because* we have SSL.
I think you meant to write that James' reasoning is circular, but strangely, your reasoning is at least as unfounded - correlation not causality. And I think the evidence is pretty much against any causality, although this will be something that is hard to show, in the absence. * AFAICS, a non-trivial proportion of credit card traffic occurs over totally unprotected traffic, and that has never been sniffed as far as anyone has ever reported. (By this I mean lots of small merchants with MOTO accounts that don't bother to set up "proper" SSL servers.) * We know that from our experiences of the wireless 802.11 crypto - even though we've got repeated breaks and the FBI even demonstrating how to break it, and the majority of people don't even bother to turn on the crypto, there remains practically zero evidence that anyone is listening. FBI tells you how to do it: https://www.financialcryptography.com/mt/archives/000476.html As an alternate hypothesis, credit cards are not sniffed and never will be sniffed simply because that is not economic. If you can hack a database and lift 10,000++ credit card numbers, or simply buy the info from some insider, why would an attacker ever bother to try and sniff the wire to pick up one credit card number at a time? And if they did, why would we care? Better to let a stupid thief find a way to remove himself from a life of crime than to channel him into a really dangerous and expensive crime like phishing, box cracking, and purchasing identity info from insiders.
Since many of the worm-spread pieces of spyware incorporate sniffers, I'd say that part of the threat model is correct.
But this is totally incorrect! The spyware installs on the users' machines, and thus does not need to sniff the wire. The assumption of SSL is (as written up in Eric's fine book) that the wire is insecure and the node is secure, and if the node is insecure then we are sunk. Eric's book and "1.2 The Internet Threat Model" http://iang.org/ssl/rescorla_1.html Presence of keyboard sniffing does not give us any evidence at all towards wire sniffing and only serves to further embarrass the SSL threat model.
As for DNS hijacking -- that's what's behind "pharming" attacks. In other words, it's a real threat, too.
Yes, that's being tried now too. This is I suspect the one area where the SSL model correctly predicted a minor threat. But from what I can tell, server-based DNS hijacking isn't that successful for the obvious reasons (attacking the ISP to get to the user is a higher risk strategy than makes sense in phishing). User node-based hijacking might be more successful. Again, that's on the node, so it can totally bypass any PKI based protections anyway. I say "minor threat" because you have to look at the big picture: attackers have figured out a way to breach the secure browsing model so well and so economically that they now have lots and lots of investment money, and are gradually working their way through the various lesser ways of attacking secure browsing. As perhaps further evidence of the black mark against so-called secure browsing, phishers still have not bothered to acquire control-of-domain certs for $30 and use them to spoof websites over SSL. Now, that's either evidence that $30 is too much to pay, or that users just ignore the certs and padlocks so it is no big deal anyway. Either way, a model that is bypassed so disparagingly without even a direct attack on the PKI is not exactly recommending itself. iang -- Advances in Financial Cryptography: https://www.financialcryptography.com/mt/archives/000458.html --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majordomo@metzdowd.com