From: Paul Foley <mycroft@actrix.gen.nz>
Date: Sun, 20 Oct 1996 08:12:32 -0700 (PDT)
To: cypherpunks@toad.com
Subject: Re: [crypto-philo]OTP or DES?
In-Reply-To: <199610200808.IAA15049@tcgcs.com>
Message-ID: <199610201246.BAA27860@mycroft.actrix.gen.nz>
MIME-Version: 1.0
Content-Type: text/plain


On Fri, 20 Oct 1995 02:45:28 -0500, walrus wrote:

   it is claimed to be an OTP.  Imagine a plaintext, encrypted with triple-des.
   It looks like a bunch of 1's and 0's to the casual observer, but to you it
   is your secret plan to take over the world.  Or so you would have us believe
   if we crack the cypher.
   actually you plan to take over the world using a completely different plan.
   It is quite easy to take the bits of the des-encrypted message, and
   calculate the OTP key nessasary to decrypt the message into your real plan.

Yes, but if you _really_ used a OTP to encrypt your real plans, the
probability that the ciphertext would decrypt via DES to anything
intelligible is so amazingly minute that no one would believe you.
It's like _one_ monkey typing out flawlessly the complete works of
Shakespeare.  On a Wednesday afternoon... :-)

   using that particular key means nothing, because a true OTP can generate
   that bit sequence.

And I can instantly break any encrypted message I see, by correctly
guessing the algorithm and the key.  I'd bet against it, though.

In fact, I don't even need to see it!!  I can guess the ciphertext, too
:-)

-- 
Paul Foley <mycroft@actrix.gen.nz>       ---         PGPmail preferred

	   PGP key ID 0x1CA3386D available from keyservers
    fingerprint = 4A 76 83 D8 99 BC ED 33  C5 02 81 C9 BF 7A 91 E8
----------------------------------------------------------------------
Fourth Law of Thermodynamics:  If the probability of success is not
almost one, it is damn near zero.
		-- David Ellis