Anthony Vandewerdt of Aussie Storage Blog comments:
Using SSH keys to perform password-free login is quite common in Unix hosts and in Appliances that have embedded Unix (like Storwize products).
You effectively have a public key which is shared and a private key (usually with a PPK extension) that is not shared. Think of the public key like the lock in your front door, that everyone can see. Think of the private key like the door key in your pocket or hand-bag. If you keep your private key secure, your door is relatively secure. If you lose your keys, your door is most likely no longer secure (unless they are down the back of the couch).
The massive increase in computational power means that generating large secure keys is trivial today. Don’t sell yourself short because a five year old document is telling you to use something small!
Read more at: Bits are cheap! Don’t sell yourself short on key length