How Geo-Encryption Makes Copyright Protection Global - ' Making of a Security '

Math Lessons

Denning was always bucking the odds. As a brainy teenager growing up in Grand Rapids, Mich., in the 1950s, Denning had been encouraged to teach high school math. Instead, she became interested in computer security while taking a seminar on operating systems as a doctoral student at Purdue University—and later married the professor who taught the class.

In the years that followed, she literally wrote the book on modern cryptography: Her Ph.D. thesis on encryption devised the now-famous "lattice model" for secure information flow so that sensitive data, such as tax records or classified information that is viewed and manipulated by software, could not be disclosed to unauthorized individuals. In the mid-1980s, at SRI, Denning developed a model for an intrusion detection system for the Navy, one of the first designed to spot real-time deviations from ordinary patterns.

But it wasn't until 1987, when Denning joined Digital Equipment Corp.'s then-new distributed systems research lab in Palo Alto, Calif., that she got her first taste of the new security threats that the Internet poses for governments and commercial interests—and wanted to do something about it. When a member of the infamous 1980s hacker group called "Legion of Doom" interviewed Denning for his 'zine, Worm, Denning became fascinated by the hacker underground, its movements, motivations and techniques. "It made me realize how little I knew," Denning recalls.

She kept in touch with the hacker community to learn more, and in 1990, she became a key defense witness against the government in a well-publicized computer case in which federal prosecutors attempted to send a 20-year-old college student to jail for 65 years because he published a purloined telephone company document in an electronic newsletter called Phrack.

Denning easily demonstrated that the information in the stolen document could not have been used to break into telephone systems and disrupt service, effectively demolishing the core of the prosecution's case.

But the experience also served to solidify Denning's conviction that existing levels of security were no match for the new world of digital-data hackers. "All of a sudden," she recalls, "it really hit me. A lot of security research had no relevance to what hackers were actually doing. We had been addressing the obscure threats, not the real ones."

Her newfound passion made her work at DEC seem less relevant, and in 1991, Denning returned to the classroom, this time as chair of Georgetown University's computer science department. There, Denning moved beyond mathematics and technology to influence the development of national security and technology policy. A short time after moving to Georgetown, Denning was invited by the National Security Agency to scrutinize the inner workings of a controversial "clipper chip" encryption code designed by the agency to enable investigators to digitally wiretap communications of hackers using strong encryption.

Six experts before Denning had declined the NSA's invitation, in part due to widespread opposition to the plan, which most felt at the time would end up giving the NSA, the nation's premier surveillance agency, increased powers to spy on citizens. But Denning, typically, refused to be swayed by public opinion. Instead, she relished the challenge as yet another intellectual puzzle to solve.

Commuting between her Washington office in Georgetown and the NSA's high-security enclave outside Baltimore, she worked from a computer workstation, trying to break code written by the government's most gifted cryptographers. After three weeks of trying, Denning was happy to report that she had failed. Her endorsement of the government's electronic code book brought a storm of criticisms from the computer hackers she once defended, with some routinely referring to her in chat rooms and listservs as the "Wicked Witch of the East."

"People suggested my books should be boycotted," Denning says. "My credentials were questioned. They said I was a dupe for the government." But Denning stood firm. "During that time, Dorothy displayed a core of toughness and a willingness to keep going despite a lot of obstacles," says Stewart Baker, the NSA's former general counsel.

Even adversaries, including privacy activist Marc Rotenberg, founder and director of the Washington-based Electronic Privacy Information Center, admired her "intellectual honesty." Says Rotenberg: "Although we clearly disagreed, she was not afraid to take unpopular positions."