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Linux Journal: Doing It All with OpenSSH, Part 2

“Welcome back to the Sysadmin’s Corner and the continuing saga
of secure communications, SSH-style. Logging in to an SSH server is
easy enough and provides you with secure communications, while
still opening you up to the whole world. You could set up a
firewall that allows in certain IP addresses only to port 22, but
that presents another problem. If you are on the road and you need
access to your own system, you might be connecting from an
untrusted system with a dynamic IP. A nice iptables rule isn’t
going to help here, unless you’ve got somebody permanently standing
by who can answer your phone call and enter the commands for
you–somebody with root access, no less. No matter how you look at
it, it can get messy.

“Another option is to leave port 22 wide open and set your
server to allow only public key authentication. This option
requires a little more work than merely running sshd and forgetting
about it. But as an added bonus, you can securely log in without a
password. Did he just say ‘without a password?’ Yes, he did, and
you can do so securely. In fact, public key authentication can be
safer than the classic password system because knowing the password
isn’t enough.

“Here’s how it works. Using a key generation program, you create
a key pair consisting of a public key, which is copied to the
server, and a private key, which you keep on your PC and guard with
your life. No authentication can take place without both
keys…”

Complete
Story

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