The paper reports on the principles involved and new developments in data encyrption. It describes available encyrption systems, with particular attention to public key cryptosystems. The problems of implementing encyrption in a data network context are considered, along with current developments in the area of national and international standards activities. Finally, the place of encyrption in the International Standards Organization Open Systems Interconnection architecture is examined. Diagrams and 11 references are included. (Author abstract modified)