Use puttygen.exe to make a private key.

Make .ssh/authorized_keys file and add text ” ssh-rsa ” with spaces,

following the public key from the private key file on one line.

Assign rw permissions only for the owner.

$ chmod 600 ~/.ssh/authorized_keys.

Configure putty to use the private key when connecting (Connection -> SSH -> Auth).

More detailed instructions: http://www.tonido.com/blog/index.php/2009/02/20/ssh-without-password-using-putty/