From: lwloen@rchland.vnet.ibm.com (Larry Loen)
Subject: Re: New Encryption Method - a Challenge!
Date: Tue, 10 Nov 1992 23:38:44 GMT
Reply-To: lwloen@vnet.ibm.com
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM Rochester

In article <n0e07t@ofa123.fidonet.org> Erik Lindano writes:

 
 >I don't want to get myself involved in the technical aspects of 
 >cryptology (-graphy?). I was simply in the process of trying to 
 >judge something that had been presented to me, and I wanted to 
 >find out whether any of the people who often write authoritative 
 >articles here about encryption, etc., are really able to actually 
 >crack a certain encryption product or whether they're just good 
 >at writing theoretical posts, that's all.

If only you knew what you were asking for!

Cryptanalysis is often successful, but the work to perform it is
often not trivial, even for systems considered worthless.  
You could be asking for dozens to thousands of hours of work
under the conditions you cite.  Yet, in spite of this
impressive-sounding total, if we succeed in such a short time
under the conditions you are giving out, we could then say
that such a system is totally worthless for virtually 
any purpose and definitely valueless commercially.

Successful designers know this and design to a stricter standard
you and your friend have not learned.  We therefore are entitled
to be strongly suspicious that your system is weak and not worth
a thousand hours of our time just to prove it to your satisfaction.
If we are wrong, we are wrong.  But, a thousand hours is a thousand
hours and before we spend it, we think we are entitled to do it 
under terms we find fairer.
 
Moreover, in any real-world situation of any importance whatever,
the algorithm WILL be known.  And, once published, it can cut down 
the amount of work from weeks to minutes!  Since we'd be providing 
a free service, shouldn't you show a little mercy?  What we are 
asking for is well within historical bounds.  In fact, if the
system is any good at all, we can even ask for much more than
the details of the algorithm.  It's in my FAQ.  There is a lot
about cryptography that is kind of counter-intuitive.  You need
to get "schooled" in it.

Also, it is sometimes possible to invent an algorithm that
encrypts but does not decrypt unambiguously.  In such a situation, 
cryptanalysis is futile, because it isn't a "real" crypto-system 
to begin with!

It's a mistake I've seen made, and it is often very difficult to
discern or prove from just the cipher text.  We could spend months
getting nowhere and then find, after your friend finally relents 
and publishes the algorithm, that it is a non-system.

It could even be a very good system . . . that was invented fifty
years ago or is a trivial variation of one invented fifty years 
ago.  We can probably TELL you that from a description of the
algorithm instead of taking hundreds of hours, perhaps giving up,
and leaving you in ignorance as to the algorithm's true value.

There is a right way and a wrong way to make the challenge.  Since
you and your friend have so far not bothered to learn the subject,
would you at least take our word for what constitutes a fair
challenge?  It's more or less in my FAQ.  If your friend will not
read it, could I ask you to do so?  You seem a fair-minded person;
only a little knowledge would allow you to ask for what you wish
much more sensibly.  You gotta learn the ground rules.

-- 
   Larry W. Loen        |  My Opinions are decidedly my own, so please
                        |  do not attribute them to my employer
Newsgroups: sci.crypt,comp.org.eff.talk,alt.privacy,talk.politics.guns