Just as it does for stock and bond prices, Goldman recently began posting digital asset prices on its Marquee platform for big clients like hedge funds, preparing for a time when the bank might be able to support trading in cryptocurrencies.In 2019, a unit of JPMorgan called Onyx introduced JPM Coin, a digital currency backed by the dollar that ran on Quorum, an internal technology that mimicked the structure of blockchain. But the bank controlled Quorum, unlike Bitcoin’s blockchain, which is decentralized. It recently spun off Quorum to a software start-up.JPMorgan also started an all-digital system that mimics the traditional “overnight repo” market, where banks exchange short-term U.S. government debt securities for cash. These transactions used to take more than a day to complete — hence the “overnight” label — but JPMorgan’s platform does them in just 15 minutes, reducing risk. It has only three users so far, and two are JPMorgan’s own businesses. Goldman this year became its first outside participant. If more banks join, JPMorgan could end up controlling one of the most crucial short-term funding markets in the world.Igor Pejic, an expert on cryptocurrencies, said JPMorgan was one of a few major banks whose experimentation with blockchain — the technology underlying digital currency transactions — has made them digital pioneers poised to profit in the future from systems they’re testing now because, he said, “they are setting up an infrastructure which at the end of the day they control.”But soon after JPM Coin went live, regulators began calling, said a person familiar with the matter who was not authorized to speak publicly. They worried that the movement of the coins around the financial system could cause a buildup of risk because they were tied to the dollar, sparking a panic and leading to the 21st century version of a bank run. The bank had to cut back on the scope of JPM Coin’s use.Now, JPM Coin cannot be used to transfer value outside JPMorgan’s internal systems. Bank customers can use it to move dollars and other assets back and forth inside the bank almost instantly, but it is meaningless in the wider world.Regulators have also trained their sights on smaller banks trying to build cryptocurrency businesses. In 2018, the New York-based Quontic Bank, with just $1 billion in assets, asked the top U.S. banking regulator, the Office of the Comptroller of the Currency, for feedback on its plans to launch a debit card program that gave customers rewards denominated in Bitcoin.