the public key minefield

[smb at research.att.com]

	 > You seem to have missed my earlier summary of how patents are struct
	ured.
	 > A separate part of the patent from the claims describes how to build
	 the
	 > claimed device.  The claims aren't supposed to.

	 Do you agree or disagree that:

	  'the concept of "anti-gravity" device is not patentable.
	   If I could duplicate the effect of your anti-gravity device without
	   using any of the same novel mechanisms.  My device would be
	   separately patentable.' ?

	 If you agree, then how can you patent "public key systems" as a
	 concept?

	 If you disagree, then we can leave it at that.

The question is phrased improperly.  Apart from the fact that the
concept (though not the reality) of anti-gravity is prior art, they
didn't patent the concept of public-key cryptography.  Rather, they
patented a class of devices fitting a certain description, with one
public key cryptosystem as an example and as a separate set of claims.
To use your analogy, I could patent anti-gravity achieved by interposing
a screen of some substance opaque to gravity, and patent Cavorite as
an instance of that class.  If you had another use for Cavorite, you'd
be home free.  Or if you found a way to neutralize gravity by beaming
anti-gravitons downward, you'd probably be clear, too.  But if you
found another substance besides Cavorite that was opaque to gravity --
yes, that would be covered by my patent.  (Fortunately, H.G. Wells didn't
patent his literary device.  But I can't think of another science
fiction author who used that technique....)

It's certainly possible that all possible cryptosystems that achieve the
same effect would be covered by their description.  That, of course, is
the mark of a good patent attorney's work -- that he or she managed to
fashion so broad a claim.  But maybe you can find a better way to do what
you really want to do, which is trade keys and authenticate messages.
And if you do -- well, then, the patent system has succeeded in its goals,
in that the monopoly assigned to someone else has stimulated you to find
another way to do things, and thus furthered the useful arts and sciences.