Re: Plaintext

Brian Murphy (
Wed, 2 Jul 1997 14:17:02 -8

> From: "Thompson, Christopher" <>
> To: "''" <>
> Subject: Plaintext
> Date: Wed, 2 Jul 1997 14:38:07 -0600

> Something's been bothering me for a few days.
> If we hadn't have known _anything_ about the plain text of the
> DES-encrypted message, we wouldn't have been able to decrypt it,
> even using brute force. Is this correct?

It would have been just as easy to hit the correct key, it just would
have been a little harder to realize when it was that you found it,
without knowing at least something about what was inside, whether it
be a known string, or knowing that it was something in English, or
whatever. If the secret message had just been itself a random series
of characters, there would have been no way to figure out if you had
the right one, or not.

It wasn't all too unrealistic of RSA to provide some known plaintext
though. In most real world applications, you'll have at least some
information about what's inside, whether it's time-stamps, or
headers, on a Word document, or whatever.


Brian Murphy
Network Engineer
Earthlink Network, Inc.