Users can authenticate ssh logins without a password by using

Public key authentication is a method used to authenticate SSH logins without the need for a password. In this approach, a pair of cryptographic keys—a public key and a private key—are generated. The private key is kept secure on the client machine, while the public key is placed in a specific file on the server (typically in the ~/.ssh/authorized_keys file of the user account accessing the server).

When a user attempts to log in via SSH, the server challenges the client to prove possession of the private key. If the client successfully responds with the appropriate cryptographic signature, the server grants access without prompting for a password. This method enhances security by eliminating the risks associated with password transmission over the network and by protecting against brute-force attacks on passwords.

In contrast, relying solely on IP addresses does not provide a method for passwordless logins; it can only restrict access based on the originating address but does not facilitate user authentication. The use of 'sudo' is unrelated to SSH logins; it is a command used to execute commands with superuser privileges and does not pertain to the authentication process for SSH sessions. The option 'none of the above' negates the correct choice by implying that there are no suitable methods