I am transfixed by the plummeting signal strength on my phone as employees of cryptocurrency exchange Coinbase close the flap of the stuffy silver tent I’m standing inside. The fabric walls enclose a cubic space about 8 feet across and contain mesh that functions as a Faraday cage, which blocks electromagnetic radiation. By the time the tent is sealed, my connection to the outside world has drained away to nothing. Now the ceremony can begin.

I’m about to witness an arcane ritual intended to bewitch Wall Street and help it fall in love with cryptocurrency.

You may have heard that bitcoin and other cryptocurrencies sets money free. The technology can transfer sums as small as a quarter-cent or as large as a quarter of a billion dollars without the need for a bank, in transactions as irrevocable as handing over cash. Proponents pitch it as an internet-era upgrade from a financial system run on dead trees, 1970s IT infrastructure, and bricks of buttery yellow metal.

But cryptocurrencies come with physical constraints of their own.

One is an unsightly environmental footprint. The computers known as “miners” that thrash through tricky math to verify bitcoin transactions consume as much energy as a small country. Another stems from a great irony: The safest way to store virtual currency is offline, in computers unconnected to the internet. To get its depositors bitcoin offline and then back on, Coinbase has devised an elaborate ceremony that generates encryption keys and prints them out on paper, which are then hidden in a reimagining of the bank vault.

Coinbase is the largest cryptocurrency exchange in the US. It has more than 20 million accounts and looks after billions of dollars worth of bitcoin, Ethereum, and other cryptocurrencies for its customers. Now it wants to lure billions more from conventional financial institutions, such as hedge and investment funds.

Coinbase generates the encryption keys that control clients' cryptocurrency inside a tent, which blocks electromagnetic signals to prevent snooping. Phuc Pham

The company’s pop-up Faraday tent and what happens inside is crucial to that offering. Institutional investors are subject to regulations that require them to place customers’ assets with a “qualified custodian.” The Securities and Exchange Commission indicated earlier this year that it is thinking about how to apply this rule to cryptocurrency. Coinbase founder Brian Armstrong wants his firm to be ready. “There’s a bunch of institutional money interested in the cryptocurrency space,” he says. “But they need a qualified institution to act as a custodian.”

Coinbase’s shielded ceremony is at the heart of that service. Ownership and control of a digital pile of bitcoin or other cryptocurrency comes down to possession of cryptographic keys, one of which might look something like this: 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa. Every now and then, the company pitches its shiny tent inside a randomly chosen secure location in San Francisco to generate and print out thousands of keys. “It takes most of a day, and we’re in there until it’s done,” says Philip Martin, Coinbase’s head of security. Custody clients transfer their assets to one of the new keys when opening an account.

Martin’s is not the only team hoping to attract Wall Street’s crypto-assets. Some institutions already send their bitcoins to Murray, Kentucky, where a small financial company called Kingdom Trust was early to offer cryptocurrency custody services. Japanese investment bank Nomura started offering its own in May. Bloomberg reported this month that Goldman Sachs is exploring doing the same. A spokesperson for the bank says the company hasn’t decided on its cryptocurrency-related offerings.

Martin and his team came up with their key-generation and storage scheme because, while cryptocurrency transactions use cryptography to prevent the same money from being spent twice, funds are still easily defrauded or stolen. The rise of bitcoin, since its creation in 2008, can be tracked by the parade of heists in which exchanges have been hacked. Computer security company Carbon Black estimates that more than $1 billion of cryptocurrency was stolen in just the first half of 2018.