On Nov 6, 2009, at 4:19 PM, Erwan Legrand wrote:

On Tue, Nov 3, 2009 at 9:41 PM, David-Sarah Hopwood
<david-sa...@jacaranda.org> wrote:
Jerry is absolutely correct that the practical result will be that most
users of OpenID will become more vulnerable to compromise of a single
password.

Do you really believe most people use different passwords for different sites?

Let's face it: most people use the same password for every single Web
site they connect to. Starting from here, I can't see OpenID becoming
much of a problem.
While I'm sure this is widely believed, I wonder if it's really true. Is anyone aware of research on the subject?

Even if it's true to a large degree, the details may matter. People may routinely use the same password for all their "low value" accounts, but come up with something better for their bank or other "high value" accounts. Paradoxically, the *lack* of a standard for password quality may help here. High-value sites often place some requirement on the nature of passwords, but the requirements vary: Letters and digits only; letters plus digits plus at least one "special" character - with the set of allowed "special" characters varying in pretty arbitrary ways; etc. It's tough to come up with a single password that will be broadly accepted at such sites, and anything someone does come up with will be so inconvenient that it's unlikely to be something they'll want to use at low-value, any- password-accepted, sites.

A widely-used single sign on system is certainly great from a usability point of view, and does actually have some positive effects on security: You no longer need to hand your actual password to sites programmed by someone whose background in security is minimal. The downside is that you now have a single super-high-value password, the compromise of which would be very painful.

                                                        -- Jerry

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