On Sep 3, 2009, at 12:26 AM, Peter Gutmann wrote:

Steven Bellovin <s...@cs.columbia.edu> writes:

This returns us to the previously-unsolved UI problem: how -- with today's users, and with something more or less like today's browsers since that's what today's users know -- can a spoof-proof password prompt be presented?

Good enough to satisfy security geeks, no, because no measure you take will ever be good enough. However if you want something that's good enough for most purposes then Camino has been doing something pretty close to this since it was first released (I'm not aware of any other browser that's even tried). When you're asked for credentials, the dialog rolls down out of the browser title bar in a hard-to-describe scrolling motion a bit like a supermarket till printout. In other words instead of a random popup appearing in front of you from who knows what source and asking for a password, you've got a direct visual link to the thing that the credentials are being requested for. You can obviously pepper and salt this as required (and I wouldn't dream of deploying something like this without getting UI folks to comment and test it on real users first), but doing this is a tractable UI design issue and not an
intractable business-model/political/social/etc problem.

Several other people made similar suggestions. They all boil down to the same thing, IMO -- assume that the user will recognize something distinctive or know to do something special for special sites like banks. Both, to me, are unproven assumptions. Worse yet, both the security literature and what I've seen of user behavior strongly suggest to me that neither scenario is true.

Peter, I'm not sure what you mean by "good enough to satisfy security geeks" vs. "good enough for most purposes". I'm not looking for theoretically good enough, for any value of "theory"; my metric -- as a card-carrying security geek -- is precisely "good enough for most purposes". A review of user studies of many different distinctive markers, from yellow URL bars to green partial-URL bars to special pictures to you-name-it shows that users either never notice the *absence* of the distinctive feature or are fooled by a tailored attack (see, e.g., the paper on picture-in-picture attacks). Maybe Camino is really better -- or maybe it just hasn't been properly attacked yet, say by a clever flash animation or some AJAX weirdness. Given the failure of all previous attempts -- who, amongst the proponents of EV certificates, realized that attackers could and would use all-green favicon.ico files to fool users -- I think the burden of proof is on the proponents.

                --Steve Bellovin, http://www.cs.columbia.edu/~smb

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