Diffie-Hellman

[Bill Stewart]

Unfortunately, Diffie-Hellman *is* patented, and I'm pretty sure Public Key Partners
(closely related to RSA) holds the patent, just as they hold RSA's.
To quote Steve Bellovin: 
	U.S. Patent Number: 4200770
	Title: Cryptographic Apparatus and Method
	Inventors: Hellman, Diffie, Merkle
	Assignee: Stanford University
	Filed: September 6, 1977
	Granted: April 29, 1980
	[Expires: April 28, 1997]
So we're stuck with it being patented until 1997.
Too bad - I was starting to think along the same lines about doing a D-H-based mailer.
It's non-trivial, if you have to worry about active eavesdroppers swapping
mail messages on you, and it's easier to do if there's a trusted Key Distribution
Center, and if you think about all the cases carefully you tend to re-create
either Needham-Schroeder or the Everhart-Osborn Bell Labs patent (~1980++),
but you can certainly do it for the common case that says the Bad Guys are
only listening to your mail and not tampering with it.

			Bill Stewart, wcs at anchor.ho.att.com