David Chaum, managing director of DigiCash, Amsterdam (31)20-665-2611. The rush is on to buy and sell on the Internet. David Chaum's company has developed a system of digital cash. Buyer's identities are kept secret and by encrypting their account numbers and transaction details, privacy and security are assured. He has developed an experimental currency trial on the Internet using "ecash", which uses "cyberbucks" as its virtual currency.