This tutorial details the steps to establish SSH authentication for connecting to a Linux machine from a Windows machine.

We assume that programs PuTTY and PuTTYgen are installed on the Windows machine.

1. Generate a pair of SSH keys. If you already have them on the Linux machine, you can skip this step. Log in to a Linux machine and generate an SSH key pair named id_rsa by

   ssh-keygen -t rsa -f id_rsa -C yourname
   

   Replace yourname by any comment you want. This will produce a public key file id_rsa.pub and a private key file id_rsa. The public key needs to be in the ~/.ssh/authorized_keys file on any Linux machine you want to connect.

2. Now we want to put the private key on the Windows machine so we can use it to connect to the Linux machine. You can use WinSCP or any other program to transfer this file to your Windows machine, or simply copy the content of id_rsa and paste to a text file on Windows. Let’s assume the private key file on Windows machine is still named id_rsa.

3. Unfortunately the private key format used by PuTTY is different from that of Linux. We use the PuTTYgen program to convert it to an appropriate format for PuTTY. Open PuTTYgen, go to menu Conversions -> Import Key, and select the id_rsa file. Click the Save private key button to save it as say id_rsa_putty.ppk. This is the private key file PuTTY will use.

4. Open PuTTY

   1. enter Host Name (or IP address)

   2. From Connection -> Data, enter your username on the Linux machine to Auto-login username.

   3. From Connection -> SSH -> Auth, load the id_rsa_putty.ppk file to Private key file for authentication.

   4. From Session, provide a session name to Saved Sessions and click Save.

   5. Now each time double-clicking the saved session will connect to the Linux machine via SSH key.