From: Eli Brandt <ebrandt@jarthur.cs.hmc.edu>
Date: Sat, 5 Mar 94 00:59:38 PST
To: cypherpunks list <cypherpunks@toad.com>
Subject: Re: Standard for SteGAnography
In-Reply-To: <Pine.3.89.9403050329.B28194-0100000@delbruck.pharm.sunysb.edu>
Message-ID: <9403050859.AA13734@toad.com>
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> Newbie questions:  What is OTP?  What about probabilistic encryption
>                    vs quantum cryptography?

OTP is one-time pad.  There was an article on quantum cryptography
in the October '92 Scientific American.  For probabilistic encryption,
I think the sci.crypt FAQ has a reference.

> How do they give one 100% certainty that they can't be broken?

OTP and some flavors of probabilistic encryption are information-
theoretically secure.  For OTP, this is obvious if you think about
it a bit.  Quantum cryptography relies on the math of quantum mechanics,
whose validity is ultimately empirical but rather well tested.

> 100% objective certainty of the scheme's invulnerability.

My point is, invulnerability to *what attack*?  An attacker may know
the algorithm, or not; may have known plaintext; may be able to
choose plaintext; may be able to read a channel, or to garble it, or
to change it; may have limited or unlimited space and time; might be
able to factor in polynomial time -- there are a lot of parameters
here.  And it makes no sense at all to say, "Well, let's just
consider the strongest possible attack."

   Eli