Matt Blaze: Finding the Hole in the Clipper Chip

In 1994 the United States government had a plan for the future of private communication: a chip, designed in secret by the NSA, that'd scramble your phone calls while keeping a spare key for the police. It was called Clipper, and a young researcher at AT&T Bell Labs found the hole in it.

Matt Blaze has spent the three decades since doing a version of the same thing to whatever catches his attention: master-keyed locks, safes, wiretap boxes, voting machines, the FBI's favorite arguments. Every few years another industry discovers that the professor with the camera has been taking its product apart.

He also owned, for 25 years, one of the most coveted domain names on the internet, and spent the last of those years fending off strangers who wanted to pay him millions for it. That story ends the way you expect. The rest of them mostly don't.

Matt Blaze at a Glance

• Blaze earned a bachelor's at Hunter College in 1986, a master's at Columbia and a Ph.D. from Princeton in January 1993, then became a researcher at AT&T Bell Laboratories.
• At Bell Labs he built CFS, an encrypting file system for Unix, and co-designed swIPe, a forerunner of the IPsec protocol that now protects internet traffic.
• In 1994 he showed that the Clipper chip's "Law Enforcement Access Field" could be forged by brute force in about 42 minutes, undermining the government's key-escrow plan.
• He coined the term "trust management," built the PolicyMaker and KeyNote systems with colleagues, and co-wrote the 1997 and 1998 reports on the risks of key recovery.
• A 2003 paper showed how to derive a building's master key from a single ordinary key, infuriating locksmiths; a 2004 follow-up applied the same thinking to safes.
• He moved to the University of Pennsylvania, directed its Distributed Systems Lab, co-wrote "Keys Under Doormats" in 2015 and joined the Tor Project's board in 2016.
• He co-founded the DEF CON Voting Village in 2017 and testified to Congress on election security in 2020; in 2018 he finally sold crypto.com, which he'd registered in 1993.
• Now the McDevitt Chair in computer science and law at Georgetown, he shared the 2023 USENIX Lifetime Achievement Award and testified on the Salt Typhoon telecom hacks in April 2025.

The Life of Matt Blaze

From Hunter College to Bell Labs

Matt Blaze collected his degrees up and down the East Coast: a bachelor's from Hunter College of the City University of New York in January 1986, a master's from Columbia in 1988, and a master's and Ph.D. from Princeton, the doctorate awarded in January 1993 for a thesis on caching in large-scale distributed file systems.

He joined AT&T Bell Laboratories, the research lab that'd already produced Unix, C and the transistor. His early projects were practical: CFS, a cryptographic file system for Unix that encrypted data transparently as it was stored, presented at the first ACM computer security conference in November 1993, and swIPe, a network-layer encryption protocol he designed with John Ioannidis that became a predecessor of IPsec.

Then the government announced Clipper.

The Clipper Chip Has a Hole

The Escrowed Encryption Standard, better known by the chip's name, used a classified NSA cipher called Skipjack and a feature nobody outside government wanted: every encrypted call carried a Law Enforcement Access Field, or LEAF, holding a copy of the session key encrypted so that agencies with the escrowed chip keys could listen in.

Blaze got his hands on prototype hardware and studied the protocol. The LEAF was 128 bits: a chip identifier, the 80-bit session key encrypted with the device's unit key, and a 16-bit checksum. Sixteen bits isn't many, and a rogue user could simply try bogus LEAFs until one passed the checksum, a brute-force search he measured at about 42 minutes on average, after which two Clipper devices could talk securely with no usable key for the government at all.

The paper, "Protocol Failure in the Escrowed Encryption Standard," appeared that November, by which time the flaw was already national news and the debate over Clipper had turned. The chip never recovered. Blaze went on to edit reports in 1997 and 1998, written with a group of the field's leading cryptographers, arguing that key-recovery systems are inherently less secure and more expensive than systems without them, work he credits with shifting U.S. encryption policy.

Trust Management

Back at the lab, Blaze asked a quieter question: how should a system decide whether to allow a dangerous action? With Joan Feigenbaum and Jack Lacy he answered it in a 1996 paper, "Decentralized Trust Management," coining the term and introducing PolicyMaker, a language for writing down who may do what.

Its successor, KeyNote, was published as RFC 2704 in September 1999 and found its way into the OpenBSD IPsec implementation. In 2000 he and Steven Bellovin, Dave Farber, Peter Neumann and Gene Spafford filed formal comments with the Justice Department on its technical review of Carnivore, the FBI's internet wiretap box.

Blaze Picks the Lock

Blaze's most notorious paper has nothing to do with computers. "Rights Amplification in Master-Keyed Mechanical Locks," published in IEEE Security & Privacy in 2003, pointed out that a master-keyed lock is essentially an authentication oracle: with one ordinary key and a few blanks, a tenant can probe a lock pin by pin and derive the master key that opens the whole building.

Blaze was told the lock industry had known about the weakness for more than half a century and kept it quiet. He published anyway, The New York Times covered it on January 23, 2003, and his inbox filled with angry letters from locksmiths.

Most of them argued both that everyone already knew and that the method was too dangerous to publish. His reply was an essay titled "Keep it secret, stupid!" In 2004 he followed up with "Safecracking for the Computer Scientist," and to this day his website carries his notes on picking pin-tumbler locks, written for his students.

From Bell Labs to Penn

By late 2004 Blaze had moved to the University of Pennsylvania, where he directed the Distributed Systems Lab and kept one foot in Washington. In 2015 he was one of the authors of "Keys Under Doormats," the paper that answered a new round of government demands for exceptional access with the same verdict as 1994: you can't build a backdoor only the good guys can use.

In July 2016 the Tor Project elected him to its board alongside Bruce Schneier and the EFF's Cindy Cohn, part of a reboot of the anonymity project's leadership.

The Voting Village

In 2017 Blaze co-founded the Voting Village at DEF CON, where attendees were handed real, decommissioned American voting machines and invited to break them. They did, repeatedly, and the village became an annual embarrassment for vendors and a resource for election officials. Blaze still chairs its board.

He testified before the House Administration Committee on January 9, 2020, about securing that year's election, and in 2020 published a Georgetown Law Technology Review article on election vulnerabilities and how to fix them. In August 2026 he was back at the village, lecturing on election security and technology.

The Domain Every Crypto Bro Wanted

Blaze registered crypto.com in 1993, when "crypto" meant cryptography, and used it as his personal website. Then Bitcoin happened.

By 2017 he was fielding offers from cryptocurrency speculators, and his site carried a disclaimer warning that "many cryptocurrencies are scams." His public reply to suitors: "just send me all your bitcoins instead. I promise to lose them for you."

In July 2018 he relented. Monaco, a Hong Kong crypto-card startup, bought the domain for an undisclosed sum that experts had pegged at up to $10 million, then renamed itself Crypto.com.

Three years later that name went up on the Los Angeles arena once known as Staples Center. Blaze's own site lives on at mattblaze.org.

Georgetown and Salt Typhoon

Blaze now holds the McDevitt Chair in computer science and law at Georgetown University, a joint appointment that matches a career spent half in the lab and half in hearing rooms. In 2023 USENIX gave him, Bellovin and Susan Landau its Lifetime Achievement Award. In 2024 the three of them and their co-authors published "Bugs in Our Pockets," a dismantling of client-side scanning proposals.

The policy fights haven't stopped. On April 2, 2025 he testified before a House Oversight subcommittee on Salt Typhoon, the Chinese intrusion into American telephone networks, and in January 2026 he, Landau and Bellovin warned in Lawfare that the U.K.'s push to reach into encrypted cloud backups could let adversaries in too.

Matt Blaze: Still Not for Sale

Thirty years after Clipper, the argument has barely changed: governments want a key, and Blaze keeps showing, with math rather than slogans, why a spare key for one side is a spare key for everyone.

He teaches at Georgetown, chairs the Voting Village, posts his photography online and keeps a blog, Exhaustive Search, whose most recent post decoded the cryptography of Little Orphan Annie's radio decoder badges.

The domain is gone. The stubbornness that kept it for 25 years isn't.