The Office of the Comptroller of the Currency (OCC) recently published a letter clarifying the authority of national banks and federal savings associations to provide cryptocurrency custody services for customers.  National and state banks and thrifts have long provided safekeeping and custody services, including both physical objects and electronic assets. In the letter, the OCC recognized that providing cryptocurrency custody services, including holding unique cryptographic keys associated with cryptocurrency, is a modern form of traditional bank activities related to custody services. The OCC also noted crypto custody services may extend beyond passively holding "keys." The OCC recognized that, as the financial markets evolve, there will be an increasing need for banks and other service providers to use technology in innovative ways to serve the need of their customers.