From: rishab@dxm.ernet.in Incidentally Next Computer's Fast Elliptic Encryption, FEE, used elliptic curves, and is patented (by R E Crandell, USP# 5,159,632,27 October 1992); Does anybody have a copy of this to see exactly what is claimed? elliptic crypto is probably covered by the DH/PKP patents. If you believe RSADSI it is. Now, are they going to say otherwise? The fact of the matter is, you can't patent ideas, nor general characteristics of devices. You can patent particular processes or mechanisms for particular purposes. If you come up with a different process or mechanism, the patent does not cover it. If you come up with a different purpose (!), the patent does not hold. The limitation to this difference is the doctrine of extension. A patent covers not only the particular thing patented but also things substantially similar to it. This is to prevent trivial changes from remaining unprotected. Another, less relevant, protection is given to inclusion. If a device includes a patented mechanism, then the patent is required to practice the device, even if the larger device is also patented. Ciphers typically do not include other specific ciphers wholesale, so this doesn't typically apply. One big exception is the blind signature, which does use specifics of RSA. This may be one of the issues with respect to restricted availability of the ecash trial in the USA. In my opinion, RSADSI is claiming far too much for their patent portfolio. In particular, claiming "all public key" is just hogwash. Elliptic curve cryptosystems certainly use a different enough mechanism not to fall under extension. El Gamal is a completely new mechanism; if RSADSI wants to claim that modular exponentiation for crypto is covered, they'll have a hard time actually arguing that one. Eric