On the Homewood campus, and beyond into the wider world of less-savvy laymen who are appalled to learn that their every keystroke may be audited by someone in Beijing or Moscow or Fort Meade, Matt Green has become the go-to guru of cyber-crypto, quoted and cited by The New York Times, the Washington Post, PBS’s Frontline, The New Yorker, and WIRED, to mention only a few.

In a world where, as he tells today’s class, anyone’s computer can be enfiladed by 30,000 hacking attempts in just a few minutes, engineering a way to exchange bulletproof envelopes of information has become a task of vital importance to individuals, businesses, governments, and nations.

Case in point: the theft of more than 70 million credit- and debit-card numbers from people who shopped at Target stores late in 2013. Among the victims: Professor Matthew Green.

“If I had to sum up what we’ve learned over the past year,” he tweeted in early March, “it’s fricking hard to stay anonymous on the Internet.”

The quest to engineer new ways to secure—or disrupt—our online lives is leading Green and his research team into twin realms, both of them prominent in recent headlines, for better or for worse: personal privacy and digital currency.

“There seems to be a growing community of people who are aware of, and are interested in, information security on the Web,” he says in an interview. “For me, when I have a thought, [I go] right into Google and I don’t think about it at the time, but then I realize that you could pretty much read my mind if you have access to what I put on there.

“Older people like my parents don’t use computers in the same way that [I do] and younger people do, so it’s not as big a problem for them. But so much of your mind goes into these devices—I’d be less concerned about someone putting a bug in my room than in one of my devices.”

Last summer, the revelations of the runaway cyber-patriot (or traitor) Edward Snowden made it shockingly clear that the National Security Agency was moving toward intercepting, auditing, and archiving every single email, text, and telephone call placed in the United States—and those made by the leaders of its putative allies abroad. Green says he was “pretty appalled. It’s clear that if the NSA wants to get you, then they can get you and there’s nothing you can do about it. But there’s also a growing feeling that there are people who want to do something about this.”

“What is the answer?” he is asked.

“The antidote is either to make people stop spying on us, which seems hard, or do something technological. Congress can only stop the ones who actually work for us.”

Thwarting all the other folks who are peeping through our digital keyholes, Green says, is a major part of the allure of Practical Cryptographic Systems.

“Some of the students really love crypto,” Green reports. “They love working on issues involving online privacy. They love the idea that you can use cryptography to do things to fundamentally change the way we interact with the electronic world—powers that would mean that nobody else can see what you’re doing.”

There was a time when the cyber-cryptographer was on a path that might have made him, if not quite the next Beethoven, then at least the first Matt Green. Raised in Vermont, just across the Connecticut River from Dartmouth University, where his mother (French) and his father (Religion and Philosophy) were professors, he remembers dinner-table arguments about computer-age ethics and Gallic literature.

“My Dad became an ethicist, and he wrote a program called ‘The Ethical Manager’ for the IBM PC,” Green says. “Depending on your answers to certain questions, it drew a big face and you could make it smile more or less.” Attracted to computers, the younger Green enrolled at Oberlin College in Ohio intending to catch the early wave of electronic music, then added computing as a second major.

“What I liked about electronic music,” he says, “is that I could sit in a lab and produce pieces without ever having to perform in public. I took three and a half years of music theory. Just like computer code, music is very mathematical and when it fits together right, it’s beautiful and when it doesn’t, it’s awful and frustrating.”

After Oberlin, Green went to work at AT&T Laboratories as the company dabbled in what he remembers as “this crazy new idea of selling music over the Internet. We were researching this question of how do you sell music securely so people can’t make copies themselves and cost us money?”

It was a question that the Apple Corporation— and not AT&T—would answer with iTunes and the portable MP3 player. About that time, Green came to an epiphany:

“Instead of implementing other people’s ideas, you could have your own.”