Martin Hellman: From Sharing Secrets to Preventing Nuclear War

Martin Hellman has spent his life on two problems that look nothing alike. The first was how two strangers could share a secret over a wire anyone might be tapping. The second is how humanity avoids blowing itself up.

He solved the first one in 1976 with Whitfield Diffie, and the answer now sits inside every secure web page on earth. The second one he's been working on since the 1980s, with a Stanford professor's tools: probability, risk analysis and a stubborn refusal to look away.

Along the way he picked a fight with the National Security Agency, nearly lost his marriage and won the biggest prize in computing. He'll tell you those three things are connected.

Martin Hellman at a Glance

• Born in New York City in October 1945, Hellman earned an electrical engineering degree at NYU in 1966 and a Stanford PhD in 1969.
• After stints at IBM's Watson lab and MIT, he returned to Stanford as a professor in 1971 and took in a wandering cryptography obsessive named Whitfield Diffie.
• Their November 1976 paper "New Directions in Cryptography" invented public key cryptography and put Hellman on a collision course with the NSA.
• In 1977 an NSA employee warned that publishing such research could amount to arms trafficking. Hellman, backed by Stanford's lawyers, presented the work anyway.
• From 1985 he turned to nuclear risk, co-editing a 1987 book with Soviet scholars and later putting a number on how often deterrence pulls the trigger in "nuclear roulette."
• In 2016 he and Diffie received the million-dollar ACM Turing Award, and that same year he and his wife Dorothie published a book that treats a marriage and the Cold War as the same problem.
• Professor emeritus since 1996, Hellman is still writing and speaking in his 80s, now about quantum computers and the odds of catastrophe.

The Life of Martin Hellman

Hellman's Early Years

Martin Hellman was born in New York City in October 1945. He studied electrical engineering at New York University, graduating in 1966, then headed west to Stanford for a master's in 1967 and a doctorate in 1969.

The career started conventionally. He spent 1968 and 1969 at IBM's Thomas J. Watson Research Center and the next two years as an assistant professor at MIT.

In 1971 Stanford hired him onto the faculty. He's been there ever since.

The Foolish Problem

Cryptography in the early 1970s was a strange thing for a young professor to care about. Nearly all serious work was classified, and the NSA regarded the subject as its property.

Hellman cared anyway. He could see that computers were about to start talking to one another over networks, and that banks, businesses and ordinary people would need secrets that didn't depend on anyone's goodwill.

Then a visitor turned up with the same conviction and no job. Whitfield Diffie had walked away from Stanford's AI lab to chase cryptography across the country, and Hellman took him into his lab.

New Directions

The two worked together through 1975, joined in 1976 by Hellman's doctoral student Ralph Merkle. The problem on the whiteboard was ancient: to share a secret, you first had to share a key, and sending the key was the dangerous part.

Their answer was to split the key. Publish one half to the world, keep the other half private, and anyone can send you a message that only you can read. The same trick, run backward, gives you a digital signature nobody can forge.

"New Directions in Cryptography" appeared in the IEEE Transactions on Information Theory in November 1976. Its first line was a promise: "We stand today on the brink of a revolution in cryptography."

The Diffie-Hellman key exchange still carries their names, though Hellman prefers to call it Diffie-Hellman-Merkle, in recognition of his student's contribution.

Apoplectic

The academic world was thrilled. The NSA, as Stanford's alumni magazine put it, was "apoplectic."

In July 1977 an NSA employee named J.A. Meyer wrote to the IEEE asserting that publishing cryptography research could violate the International Traffic in Arms Regulations. "These modern weapons technologies, uncontrollably disseminated," he warned, "could have more than academic effect."

Hellman took the letter to Stanford's counsel, John Schwartz, who advised that publishing would most likely break no law. Later that year Hellman went to a symposium at Cornell and presented the work of his students Merkle and Pohlig himself.

The same year he and Diffie published "Exhaustive Cryptanalysis of the NBS Data Encryption Standard," arguing the new government cipher's 56-bit key was too short. The magazine later described how the NSA had pushed IBM to shorten it, a role the agency's director denied in 1979 and declassified documents eventually confirmed.

Knapsacks and Trade-offs

Hellman kept publishing. In 1978 he and Merkle proposed a public key system built on "trap door knapsacks," and in 1980 he described a cryptanalytic time-memory trade-off, a way of spending storage to save computing time that password-cracking tools still build on.

Something else changed in those years. Hellman had seen the NSA as an enemy, but a meeting with Admiral Bobby Ray Inman, who ran the agency, convinced him the two sides had more in common than either admitted.

Looking at a conflict from both sides, he later said, "resolved an apparently intractable impasse." It was a lesson he'd use again.

Beyond War

In 1985 Hellman published a paper with a blunt title, "On the Inevitability and Prevention of Nuclear War," and shifted most of his attention from ciphers to the arms race.

He joined the Beyond War movement and, in 1987, co-edited Breakthrough: Emerging New Thinking with the Soviet scholar Anatoly Gromyko, a collection published in both Russian and English at the height of the Cold War.

His wife, Dorothie, a former accountant at Touche Ross, became vice president of fundraising at the Beyond War Foundation. The two of them were also, at the time, barely speaking.

About a decade into the marriage they came close to divorce. The way back, they've both said, ran through a group called Creative Initiative and a rule they still repeat: "Get curious, not furious."

Nuclear Roulette

Hellman's second career is an engineer's answer to a political question. In 2008 he published "Risk Analysis of Nuclear Deterrence," treating the bomb the way a safety engineer treats a reactor, as a system with a failure rate.

His estimate, he told InfoWorld in 2024, was that the risk of a major nuclear war was roughly equivalent to pulling the trigger in "nuclear roulette" once every fifteen years. With the conflicts of recent years, he argued, the trigger is being pulled closer to once a year.

He's made the case in the Bulletin of the Atomic Scientists and in essays timed to the anniversaries of the Cuban Missile Crisis, the most recent in October 2022, titled "Time to Stop Playing Russian Roulette."

A Prize and a Map

On March 1, 2016, the Association for Computing Machinery announced that Hellman and Diffie had won the 2015 A.M. Turing Award, with a $1 million prize mostly funded by Google. The FBI was fighting Apple over an encrypted iPhone that week, and both laureates said a government back door would put everyone at risk.

The same year the Hellmans self-published A New Map for Relationships: Creating True Love at Home and Peace on the Planet. Its first chapter is about a road map Martin took from Dorothie "to help," and which she tore to pieces.

They pieced it back together, which is roughly the book's argument about nations too. "What got us initially started was not wanting to save the world," Hellman told Dark Reading. "It was wanting to save our marriage."

Hellman Today

Hellman has been professor emeritus at Stanford since 1996, which hasn't slowed him down. He and Dorothie have been married for more than 56 years and have given talks together for years.

In June 2026, fifty years after the paper, Cybernews marked the anniversary by asking how the invention will hold up against quantum computers. The short answer is that the world is now busy replacing the locks the two of them built.

He keeps a page at Stanford that lists his papers, his awards and, with equal weight, his work on "rethinking national security." He doesn't consider the two halves of his life separate.

Martin Hellman: Get Curious, Not Furious

The young professor who ignored every warning and published anyway turned out to be right about the internet before the internet existed. Then he spent forty years asking whether the species would be around to use it.

What ties the halves together is a habit: when the other side looks crazy, go find out what they're actually thinking. It worked with the NSA. It worked at his kitchen table.

He's still trying to make it work for the rest of us.