how to use public key n private key for login authentication

Hi,
 
I am working on authentication of Login using public key and private key using C++/MFC.
 
I am new to generation of public key n private key. How to create these keys and how
 
to use these keys for login authentication. As it is a Login, need to create a pair of
 
public key and private key for each user and encrypt the password and decrypt the
 
password at later stages. Can one help me to how generate the key pairs and how to use
 
them. I am very thankful to him.