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microsoft research drm talK
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where every character is rotated halfway through the alphabet.
They used to do this with non-worksafe material on Usenet, back
when anyone on Usenet cared about work-safe-ness — A would
become N, B is O, C is P, and so forth. To decipher, you just add 13
more, so N goes to A, O to B, yadda yadda.
Well, this is pretty lame: as soon as anyone figures out your
algorithm, your secret is g0nez0red.
So if you’re Caesar, you spend a lot of time worrying about
keeping the existence of your messengers and their payloads
secret. Get that? You’re Augustus and you need to send a message
to Brad without Caseous (a word I’m reliably informed means
“cheese-like, or pertaining to cheese”) getting his hands on it.
You give the message to Diatomaceous, the fleetest runner in the
empire, and you encipher it with ROT-13 and send him out of the
garrison in the pitchest hour of the night, making sure no one
knows that you’ve sent it out. Caseous has spies everywhere, in
the garrison and staked out on the road, and if one of them puts
an arrow through Diatomaceous, they’ll have their hands on the
message, and then if they figure out the cipher, you’re b0rked. So
the existence of the message is a secret. The cipher is a secret. The
ciphertext is a secret. That’s a lot of secrets, and the more secrets
you’ve got, the less secure you are, especially if any of those secrets
are shared. Shared secrets aren’t really all that secret any longer.
Time passes, stuff happens, and then Tesla invents the radio
and Marconi takes credit for it. This is both good news and bad
news for crypto: On the one hand, your messages can get to
anywhere with a receiver and an antenna, which is great for the
brave fifth columnists working behind the enemy lines. On the
other hand, anyone with an antenna can listen in on the message,
which means that it’s no longer practical to keep the existence of
the message a secret. Any time Adolf sends a message to Berlin,
he can assume Churchill overhears it.
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