Which utility is used to create public and private key pairs for SSH authentication?

`adduser` is a command used to create new user accounts on a Linux system, not to generate cryptographic key pairs.

The `ssh-keygen` command is the standard utility on Unix-like operating systems that creates new public and private key files, which are essential for establishing secure, passwordless SSH connections based on public key cryptography.

While 'keygen' refers to a key generator, `ssh-keygen` is the precise and correct utility name for generating SSH keys.

`ssh` is the client program used to initiate a secure shell connection to a remote server, not to generate the underlying authentication keys.