About SSH Keys
SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. While a password can eventually be cracked with a brute force attack, SSH keys are nearly impossible to decipher by brute force alone. Generating a key pair provides you with two long string of characters: a public and a private key. You can place the public key on any server, and then unlock it by connecting to it with a client that already has the private key. When the two match up, the system unlocks without the need for a password. You can increase security even more by protecting the private key with a passphrase.
verify your ssh pub key below cmd # cat ~/.ssh/id_rsa.pub
Make sure have you have safe backup copy following files ~/.ssh/id_rsa.pub and ~/.ssh/id_rsa In case of OS crash or system changed we need to use same id_rsa.pub ,id_rsa keys . Those keys we are going to map for required servers access for individual ssh logins
If not yet generated ssh keys follow the link https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys--2
#As per gopal request removed ssh public keys removed from this page