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Computers, printers, and high-rate data-transmission facilities are becoming less expensive and more generally available. It is now possible to distribute customized newspapers and magazines electronically, instead of using a fleet of trucks and a network of vendors to disseminate a common paper version. A major obstacle to the use of electronic distribution is the ease of copying and redistributing electronic documents. This capability can affect a publisher's subscription revenues. The AT — Using cryptographic techniques, so the form of the document, available to a recipient, costs more to redistribute than that disseminated by the publisher; and — Requiring someone who redistributes a document to divulge personal, identifying information with the document. These techniques are being applied in experiments to distribute an issue of a technical journal electronically, and to mark and register paper copies of confidential executive memoranda.
N.F. Maxemchuk (Sat,) studied this question.