Thursday, May 07, 2009

How to guarantee bad passwords (part 2)

As I described in a recent post, overly complex password rules lead to hard-to-remember passwords that get written down. Well, I tried not to write it down, and promptly forgot it. So I called the helpful help desk person, who reset it for me to a random value, and had me reset the password. Other than the cost to the organization of having to have a person involved in password resets, so far so good.

But then the kicker: your new password can't have any two character sequence the same as any of your previous 9 passwords. Makes sense to some extent - you shouldn't be able to switch from "myDOGspot!!" to "myDOGspot??". However, it means that in order to do this check, they're almost certainly not storing one-way hashes of the passwords (as good security engineers do), but rather the original passwords. The help desk person assured me that the passwords are encrypted, so there's nothing to worry about. So even if someone breaks into their site, all they'd get is the encrypted passwords.... Of course, if someone figures out how to get in below the level of encryption, then game over.

Moral of the story: "improving" security by strong passwords can backfire in many ways, by causing users to write them down, having servers that store the original passwords, etc.


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