From the user's point of view, SSH consists of several client programs and some configuration files. The most commonly used clients are ssh for remote login, and scp and sftp for file transfer. Authentication to the remote host can be accomplished using existing login passwords or with public-key cryptographic techniques. Passwords are more immediately and easily used, but public-key authentication is more flexible and secure. The ssh-keygen, ssh-agent, and ssh-add programs generate and manage SSH keys.