Have a look at this link https://help.github.com/articles/working-with-ssh-key-passphrases/
But I don’t want to enter a long passphrase every time I use the key!
Neither do I! Thankfully, there’s a nifty little tool called
ssh-agentthat can save your passphrase securely so you don’t have
to re-enter it. If you’re on OSX Leopard or later your keys can be
saved in the system’s keychain to make your life even easier. Most
linux installations will automatically start ssh-agent for you when
you log in.