....
The authenticity of the user is verified against 2 factor authentication. The first factor is validation of 3 different AD attributes. User will need to provide 3 different information which only he will know such as Home Telephone, Pin Code or any new AD attribute say PIN, Date of Birth, Date of Joining etc.
The second factor is One Time Password (OTP). After successful validation of First Factor, a OTP is sent to the Email address of the user, may it be official or personal.