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Public key authentication is more secure than password authentication. This is particularly important if the computer is visible on the internet. If you don’t think it’s important, try logging the login attempts you get for the next week. My computer – a perfectly ordinary desktop PC – had over 4,000 attempts to guess my password and almost 2,500 break-in attempts in the last week alone.

With public key authentication, the authenticating entity has a public key and a private key. Each key is a large number with special mathematical properties. The private key is kept on the computer you log in from, while the public key is stored on the .ssh/authorized_keys file on all the computers you want to log in to.