Google shows one "geo-encryption" patented by CoinCard, which may or may not be a component of Denning's geo-crypto. Because CoinCard is a Canadian company, its geo-encryption may have nothing to do with Denning's. CoinCard uses a system composed of a swipe card and passive card reader to decrypt, described in a programmers' manual: http://www.coincard.com/download/ProgrammerManual.pdf It looks as though these readers could be rigged for GPS transceiving to assure that encrypted data was physically located where intended by the sender, and/or the recipient's card could be programmed to be read only by that card reader. Is this a novel system? How to spoof GPS location? Can bin Laden be in several caves around the world each equipped with a personal-ID GPS passive transceiver? Do caves serve as acoustic resonators to emit recorded whispers up ventilating shafts? What underling was wearing Rumfeld's personal tracker on 9/11? Why was the SecDef frantically trying to recover it before Mrs. Rumfeld's private investigators? And his secondary tracker?