On Wednesday 01 June 2005 10:35, Birger Tödtmann wrote:

Am Dienstag, den 31.05.2005, 18:31 +0100 schrieb Ian G: [...]

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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 never will be..."? Not being economic today does not mean it couldn't be economic tomorrow. Today it's far more economic to lift data-in-rest because it's fairly easy to get on an insider or break into the database itself.

Right, so we are agreed that listening to credit cards is not an economic attack - regardless of the presence of SSL. Now, the point of this is somewhat subtle. It is not that you should turn off SSL. The point is this: you *could* turn off SSL and it wouldn't make much difference to actual security in the short term at least, and maybe not even in the long term depending on the economic shifts. OK, so, are we agreed on that: we *could* turn off SSL, but that isn't the same thing as "should* ? If we've got that far we can go to the next step. If we *could* turn off SSL then we have some breathing space, some room to manouvre. Some wiggle room. Which means we could modify the model. Which means we could change the model, we could tune the crypto or the PKI. And in the short term, that would not be a problem for security because there isn't an economic attack anyway. Right now, at least. OK so far? This means that we could improve or decrease its strength ... as our objectives suggest ... or we could *re-purpose* SSL if this were so desired. So we could for example use SSL and PKI to protect from something else. If that were an issue. Let's assume phishing is an issue (1.2 billion dollars of american money is the favourite number). If we could figure out a way to change the usage of SSL and PKI to protect against phishing, would that be a good idea? It wouldn't be a bad idea, would it? How could it be a bad idea when the infrastructure is in place, and is not currently being used to defeat any attack? So, even in a stupidly aggressive worst case scenario, if were to "turn off SSL/PKI" in the process and turn its benefit over to phishing, and discover that it no longer protects against listening attacks at all - remember I'm being ridiculously hypothetical here - then as long as it did *some* benefit in stopping phishing, that would still be a net good. That is, there would be some phishing victims who would thank you for saving them, and there would *not* be any Visa merchants who would necessarily damn your grandmother for losing credit cards. Not in the short term at least. And if listening were to erupt in a frenzy in the future it would likely be possible to turn off the anti-phishing tasking and turn SSL/PKI back to protecting against eavesdropping. Perhaps as a tradeoff between the credit card victim and the phishing victim. But that's just stupidly hypothetical. The main thing is that we can fiddle with SSL/PKI if we want to and we can even afford to make some mistakes. So the question then results in - could it be used to benefit phishing? I can point at some stuff that says it will be. But every time this good stuff is suggested, the developers, cryptographers, security experts and what have you suck air between their teeth in and say you can't change SSL or PKI because of this crypto blah blah reason. My point is you can change it. Of course you can change it - and here's why: it's not being economically used over here (listening), and right over there (phishing), there is an economic loss waiting attention.

However, when companies finally find some countermeasures against both attack vectors, adversaries will adapt and recalculate the economics. And they may very well fall back to sniffing for data-in-flight, just as they did (and still do sometimes now) to get hold of logins and passwords inside corporate networks in the 80s and 90s. If it's more difficult to hack into the database itself than to break into a small, not-so-protected system at a large network provider and install a sniffer there that silently collects 10,000++ credit card numbers over some weeks - then sniffing *is* an issue. We have seen it, and we will see it again. SSL is a very good countermeasure against passive eavesdropping of this kind, and a lot of data suggests that active attacks like MITM are seen much less frequently.

All that is absolutely true, in that we can conjecture that if we close everything else off, then sniffing will become economic. That's a fair statement. But, go and work in one of these places for a while, or see what Perry said yesterday:

The day to day problem of security at real financial institutions is the fact that humans are very poor at managing complexity, and that human error is extremely pervasive. ....

I'm sure that you'll agree that the likelihood of them closing of all the other attacks is next to nil. Even if some top flight security experts manages to find a client that really cares about security and they together manage to actually lock everything down (a rather low probability, I'd suggest) then there will still be 1000 other places for the attacker to steal the data. The day to day reality of financial institutions is that they do not have good protections in place, they have *adequate* protections for what they *know* about. Which means that there is plenty of pickings out there. So I would suggest that listening for credit cards will never ever be an economic attack. Sniffing for random credit cards at the doorsteps of amazon will never ever be an economic attack, not because it isn't possible, but because there always likely to be easier pickings elsewhere. But don't get me wrong - I am not saying that we should carry out a world wide pogrom on SSL/PKI. What I am saying is that once we accept that listening right now is not an issue - not a threat that is being actively dedended against - this allows us the wiggle room to deploy that infrastructure against phishing. Does that make sense? iang PS: nor does it matter whether I'm right or I'm wrong about my prediction that sniffing will be an economic attack or not - it's just a prediction about the future, just a hypothetical estimate. What matters is now: what attacks are happening now. Does phishing exist, and does it take a lot of money? What can we do about it? -- 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