How To Use Key Authentication To Prevent Unauthorized Logins To Your Linux Instance

At our cloud provider, we take security seriously, and one of the best ways to ensure the security of your server is by using public key authentication. Public key authentication is a way to authenticate users without the need for a password. Instead, users generate a public/private key pair, and the public key is placed on the server while the private key is kept secret by the user.

Here are the steps to set up public key authentication on your Linux-based server:

Step 1: Generate a key pair

The first step is to generate a public/private key pair on your local machine. You can do this using the ssh-keygen command:

$ ssh-keygen -t rsa

This command will generate a 2048-bit RSA key pair and save the keys in the ~/.ssh directory on your local machine.

Step 2: Copy the public key to the server

Once you have generated your key pair, you need to copy the public key to the server. You can do this using the ssh-copy-id command:

$ ssh-copy-id user@server_ip_address

This command will copy your public key to the server and add it to the authorized_keys file, which is a file that lists all the public keys that are authorized to access the server.

Step 3: Disable password authentication

To ensure maximum security, it is best to disable password authentication on your server. You can do this by editing the sshd_config file:

$ sudo nano /etc/ssh/sshd_config

Find the line that says PasswordAuthentication and change its value from yes to no. Then save and exit the file.

Step 4: Test the connection

Now that you have set up public key authentication and disabled password authentication, you can test the connection. Try to connect to your server using the ssh command:

$ ssh user@server_ip_address

If everything is set up correctly, you should be able to connect to the server without entering a password.

In conclusion, public key authentication is a secure and efficient way to authenticate users on your Linux-based server. By following the steps outlined in this guide, you can set up public key authentication and prevent unauthorized logins. If you have any questions or need further assistance, please don't hesitate to contact our support team.