by Dorothy E. Denning

About the author: Dorothy E. Denning is a computer science professor at Georgetown University in Washington, D.C., and a specialist in computer and communication security. Denning was consulted by the federal government to review its Clipper encryption system.

Imagine you are the program manager for a new, energy-efficient airplane. You fax the design plans to the manager of an overseas plant that will manufacture parts of the plane. You also discuss the design by phone with engineers in the plant. A few months later, your company loses a bid for a fleet of planes to an overseas competitor who proposed a nearly identical design. The rival stole your plans by intercepting your voice and fax communications.

Fortunately, electronic communication can be protected against such industrial espionage with encryption—scrambling of data...