Step One—Create the RSA Key Pair
The first step is to create the key pair on the client machine (there is a good chance that this will just be your computer):
ssh-keygen -t rsa
Step Two—Store the Keys and Passphrase
Once you have entered the Gen Key command, you will get a few more questions:
Enter file in which to save the key (/home/demo/.ssh/id_rsa):
You can press enter here, saving the file to the user home (in this case, my example user is called demo).
Enter passphrase (empty for no passphrase):
It's up to you whether you want to use a passphrase. Entering a passphrase does have its benefits: the security of a key, no matter how encrypted, still depends on the fact that it is not visible to anyone else. Should a passphrase-protected private key fall into an unauthorized users possession, they will be unable to log in to its associated accounts until they figure out the passphrase, buying the hacked user some extra time. The only downside, of course, to having a passphrase, is then having to type it in each time you use the key pair.