Storing users passwords

I am currently designing a system that involves customer logins.  One possible login step is entering 3 random chars from the password.

I know typically. passwords are stored as a hash.  However, it is impossible to use 3 random chars with this method.  Can anyone tell me how the passwords should be stored without storing them as plain text?
benmanningAsked:
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Rich RumbleConnect With a Mentor Security SamuraiCommented:
So you want "Two-Factor" authentication... there are a number of ways to do this. While it's a good second measure, with phishing and man-in-the middle, it's not a guarantee, but I feel it adds to the security somewhat. I recommend reading: http://www.schneier.com/blog/archives/2005/03/the_failure_of.html
For your system to ask for 3 random characters from the users password, it should, naturally ask for those first, and the password second. You can store a password in a reversible encryption, and there are other novel methods people are trying for two-factor auth, similar to "captcha" those squiggly text boxes no human can read: http://www.popsci.com/files/imagecache/article_image_large/files/articles/google_captchas_485.jpg
Automated systems are better at solving those than we are, but they have more trouble with questions, like
what is two + 2? or this is a picture of an... "owl" this was made more popular by "kittenauth" where you pick the pictures of kittens http://www.mattwardman.com/blog/wp-content/uploads/20070614-kittenauth-screenshot-1.jpg
http://www.schneier.com/blog/archives/2006/04/kittenauth_1.html
-rich
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ahoffmannCommented:
> .. to use 3 random chars with this method.
no, except brute force
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