Key length security (calculations!)

[solman at MIT.EDU]

[I describe the shamir triple pass key exchange protocol]

> I suspect this protocol is covered by the Diffie-Hellman patent, which is
> quite broad, covering many sorts of key exchanges.  Diffie-Hellman is now
> owned by PKP, the sister company to RSA.  If so, Shamir has not undercut his
> own financial interests by this work.  (Also, this does not obsolete PK
> since it requires several exchanges before communication can occur, making
> it inappropriate for high-latency communications, such as for most email.)

Can anybody verify this? I thought that DH only applied to public key systems.
Surely the idea of exchanging keys can't be patented. You have to patent the
process and I though DH just took care of the public key symetric key exchange 
process.

JWS