set up putty key login

1. generate key pair from server side or from putty side
   ssh-keygen
2. put public key into serverside
    cat id_rsa.pub >> ~/.ssh/authorized_keys2
    remove your email from the end.
   
3. set up putty session with private key.


reference:
http://www.howtoforge.com/how-to-configure-ssh-keys-authentication-with-putty-and-linux-server-in-5-quick-steps