SSH can automatically authenticate connections when the client presents an authorized key. A client gives it’s public key to a server and then when it connects the server knows it’s allowed in and automatically allows the connection. The Keys are specific to users, so a key for user_a will not let user_b in.
Few Simple Steps
If the keys don’t exists already you must create them. Look in your ~/.ssh for files called id_rsa and id_rsa.pub. If those files don’t exist say ssh-keygen -b 2048 -t rsa to create them.
Place Keys on Server
Copy id_rsa.pub to the server then append that to ~/.ssh/authorized_keys
Optionally you can use a DSA key, simply replace `rsa` with `dsa` above