Password-less SSH via PuTTY

I need to connect to a Ubuntu 10.10 server via PuTTY, password-lessly.

You can generate the key pair from two places:

• On the Unbuntu server by using ssh-keygen. Detail
• On the local machine, using a utility called PuTTYgen

But using either way alone won't work because:

1. PuTTY only understands the private key file generated by PuTTYgen. PuTTY complains if I select a private key generated by ssh-keygen (on the server).
2. Ubuntu OpenSSH doesn't understand the public key generated by PuTTYgen. The server will give you Server refused our key if I copy the public key generated by PuTTYgen.

The solution is tricky but simple: all I need to do is, generate the key pair on the server by using ssh-keygen. Copy the generated private key to local machine, and load it to PuTTYgen, then convert it into PuTTY format. That's all!