A century ago, a commuter train carrying hundreds of passengers from Park Row to Brighton Beach, New York, took a perilous stretch of rail at seven times the appropriate speed.

At the controls was Edward Luciano, a young and inexperienced driver with only two hours of training, brought in as a substitute to cover a strike. As chronicled in Uptown, Downtown, a 1976 book by Stan Fischler, Luciano was defeated by the confusing braking system, and the train derailed on a jinking set of curves, killing at least 93 people and injuring hundreds more.

The wreck led to a raft of safety improvements, among them, it is believed, the dead man’s switch, a fail-safe now found in all kinds of modern machinery. A dead man’s switch can take the form of a handle or pedal to which force must be continuously applied, or a button that has to be pressed at intervals, but the principle is the same: If the human operator fails to respond, the machine shuts down.

In 2017, another New Yorker, Zach Hamilton, began to wonder how the same concept might be applied to the digital realm. He had identified a problem: People were getting locked out of their cryptocurrency wallets without any means of recovering access, and their heirs were finding it difficult to access their digital assets after they died. Billions of dollars’ worth of crypto has been lost this way. Hamilton figured that a digital dead man’s switch, which would release a document payload instead of switching off a machine, could help someone to recover their wallet or pass credentials to an inheritor without having to trust a third party. In theory, it could be used for all manner of other things, too. For years, a “quick and dirty” sketch sat dormant on Hamilton’s computer, he says. But when New York locked down for the Covid pandemic, he began to develop his idea. He called it Sarcophagus.

Hamilton was not the first to come up with a digital dead man’s switch. These kinds of services have been available for years from providers such as Stochastic Technologies. Firms including Google and Microsoft offer similar functionality, letting users nominate someone to inherit their account after a period of inactivity. The primary difference is that Sarcophagus is built atop crypto technology, meaning the contents of users’ documents are never visible to a third party and that the availability of their payloads does not depend on the service provider remaining in operation.

It works like this: A user submits a file via the Sarcophagus web app, specifies a recipient, and sets a timeframe. Then they agree to pay one or more fellow users to act as the file’s protector and post the fee in escrow. The file is encrypted and sequestered in a decentralized file storage network called Arweave, which aims to store information permanently by incentivizing people to contribute their own hard drive space. If the user fails to make an attestation proving they are alive within the timeframe, the file is released to the recipient and decrypted using a combination of their own credentials and those of the chosen protector. Only after the file has been successfully handed on does the protector receive the payment.

The system, says Hamilton, is designed to be “anti-fragile,” meaning it depends on no party’s good will to achieve its end. Nobody but the originator and recipient have access to the contents of the file, all other parties are financially incentivized to cooperate, and redundancies ensure the payload is always available. “Little strings of data control our lives,” says Hamilton. Because humans are “gooey”—that is, unreliable and prone to mistakes—the only sensible protection for those strings is cryptography, he adds.

There are various other ways, says Hamilton, that Sarcophagus might be applied outside of a crypto setting. A digital dead man’s switch could be used by a whistleblower to release incriminating material or by a dissident or journalist who suspects a threat to their life, as a kind of SOS. In a more mundane context, it could be used to pass account credentials from one generation of employees to the next.

Sarcophagus has received $6 million in funding to date from investors including Placeholder, Blockchange, and Hinge Capital. The project is managed by a decentralized autonomous organization, or DAO—a collective that governs the Sarcophagus treasury and development process through a system of community voting. In its present state, Sarcophagus is best described as an “early beta,” says Hamilton. The service is operational but not widely used, and it does not generate significant revenue—only a small cut of every payment.

One barrier to broader adoption is that recipients must already have access to a crypto wallet, whose credentials are used to decrypt the data payload. There is an option to create a new wallet for someone, along with a PDF walking them through the process for accessing it, but a level of crypto literacy would certainly help.

As the generation of people comfortable with crypto grows older and begins to reckon more seriously with their mortality, Hamilton thinks a larger subset will begin to understand the need for a service like Sarcophagus. “Millennials are just starting to think about this problem,” he says. Hamilton imagines that more accessible services will be built atop Sarcophagus technology, too. These “boomer products,” as Hamilton calls them, one of which his own team is developing, will abstract away some of the technical complexity, such that people won’t realize they are using crypto infrastructure. (Although there is an inevitable trade-off between security and convenience.)

In any case, says Hamilton, the present system—whereby credentials to high-value crypto wallets might be stored in bank vaults protected by armed guards—approaches the absurd. The “billion-dollar file cabinet” has to go, says Hamilton. “We are still relying on heavy metal doors and guys with guns when cryptography itself can act as a steel wall of incredible thickness.”

This article originally appeared in the May/June 2024 issue of WIRED UK.