When was the last time you sent a coded message? Well, probably within the last hour, if you’ve
sent an email or logged onto a website. We use codes all the time because we communicate
our private messages in public. Without codes, sending information online
over unsecured networks or networks with security holes would be like standing in Times Square
and shouting your innermost secrets at the top of your lungs, in a crowd of millions
of people doing the exact same thing. So to protect your privacy, you have to send
your messages as codes that can be read by your friends, but not by your enemies. Codes have played a critical role in just
about every major war in recorded history. In ancient Rome, Caesar used a simple code
to send messages to his generals. Two thousand years later, Allied code breakers
saved millions of lives and shortened World War II by cracking the German Enigma code. But codes aren’t just for emperors and soldiers;
today we use them to shop online and say hi to our friends. Let’s say you want to share a secret with
a friend. Here’s what happens after you hit send on
an encrypted email. First, your email services need to agree on
a secret key—a very large number—that will be used to lock and then unlock your
message. But they can’t just send that number over
the internet—an eavesdropper could intercept it. So they use a brilliant trick called public
key cryptography. Both sides start with a publicly available
number, but then add a dash of their own secret numbers and mix them together using mathematical
operations that are extremely difficult to reverse. They swap bowls and do it again—dash of
secret number, mix it up, and bam! Secret key. They used the same recipe, but never shared
their individual secret ingredients, so the key is safe. Now your email service uses that secret key
to transform and scramble your message. It transmits the coded message to your friend’s
email service, which uses the secret key to reverse the scrambles and transformations
and reveal the original text. Phew. That’s a lot of work for one email, but
it happens in the blink of an eye and without any effort on your part. The scary thing is, not all traffic is encrypted. Online payments usually are, but browser history
is not, nor are many text messages. Emails are complicated—they’re usually
encrypted when they’re sent, but are sometimes decrypted before they get to their recipient. Some websites encrypt their traffic; you can
tell by looking for the lock symbol in a URL. If it’s not there, anything you type into
that website can be intercepted. That’s one of the reasons it is so important
to have a different password for every website you visit and to avoid unsecure public Wi-Fi—where
your messages can be easily intercepted. The other problem is: almost every code in
history has been cracked in a way that initially seemed impossible. It could be the case that there is a chink
in the armor of the codes we use that no one has discovered yet. Or perhaps someone has, and is keeping that
information to themselves. So the next time you metaphorically shout
your innermost secret in public, take a moment to consider whether you’ve locked it up
tight enough—and what could happen if it got out.