It is important that any remote access to an Ubuntu system be implemented in a way that provides a high level of security. By default, SSH allows remote system access using password-based authentication. This leaves the system vulnerable to anyone who can either guess a password, or find out the password through other means. For this reason, the use of key-based authentication is recommended to protect system access. Key-based authentication uses the concept of public key encryption involving public and private keys. When implemented, users are only able to connect to a server if they are using a client which has a private key that matches a public key on the server. As an added layer of security, the private key may also be encrypted and password protected. Once key-based encryption has been implemented, the server system is then configured to disable support for the less secure password-based authentication.
This chapter has provided an overview of SSH key-based...