getting the password from Active Directory and partial password verification.

I am trying to write an asp .net login verification system which asks users to login with a random selection of letters from the users password.
e.g if the password was experts, they are asked to supply 1,2 6 and they would have to supply e,x and t.
I am combining it with a record of their last used i.p address and if that changes a mobile phone sms security pin confirmation.
My problem is I cannot find a way of accessing the password from active directory to construct the partial match authentication or a way to test the 3 letters against the password for partial match and this may not be possible.
My alternative is to force our users to supply a different login password for the login system or we manually set it in an accessible field.
Is there a way to achieve what I need without taking these steps?
Regards,
dgloverukAsked:
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Guy LidbetterCommented:
Hi there,

AD does not store a copy of the users password, only a hash which is generated using the entire phrase. So there would be no way of achieving this.

This type of login is generally a second factor auth of which a plain text or encrypted password can be recalled and compared for specific characters post the user providing a full username\password login.

Regards

Guy

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dgloverukAuthor Commented:
Thanks Guy,
If it is not possible then that's the answer :)
Regards,
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