SSH keys are used to secure access to and authenticate authorized users to remote servers. They are stored locally on the client machine and are encrypted using public-key cryptography. These keys are used to encrypt communications between the client and server and provide secure remote access.
When you log into a remote machine, you must provide a valid private key to decrypt the traffic. As long as the private key remains secret, only you can access the server. However, if someone obtains your private key, they can impersonate you on the network.
SSH key rotation helps prevent this type of unauthorized access. It reduces the risk that someone has access to your private key, and helps prevent malicious users from being able to impersonate you on your network.
Most security policies and best practices call for rotating your key files on a periodic basis, ranging from yearly to quarterly, depending on the sensitivity of the data on the system. Such policies go a long way to ensuring the security of authentication credentials and the authentication process for sensitive machines.
There are two ways to rotate your keys: manually, and automatically.
To manually perform key rotation, you need to generate a new pair of keys. Each time you do this, you create a new key pair. You then upload the public key file to the server you wish to connect to. Once uploaded, the server uses the public key to verify that you are who you say you are.
An alternative approach is to use automatic key rotation. With automatic rotation, you don’t need to generate a new key pair each time you change your password. Instead, you simply update the permissions on your existing key file.
The following steps show how to configure automatic rotation.
1. Generate a new keypair
2. Upload the public key to the remote server
3. Configure the remote server to use the new keypair
4. Update the permissions on the old keypair file
5. Delete the old keypair
6. Logout from the remote server
On Linux systems, use the “man” command to learn more about the following:
- ssh-keygen command
- ssh-public-key command
- upload-ssh-public-key command
The examples should provide options for command parameters and sample command output for your operating system.
For more information about the SSH protocol, you can review the Wikipedia article here.