The battle between the crypto community and the U.S. government over financial privacy just escalated dramatically, amid government efforts to crack down on criminals. Tornado Cash is a service that helps some cryptocurrency owners protect their anonymity by scrambling information trails on the blockchain. On Monday, the Treasury Department prohibited Americans from using the service, arguing that it has played a central role in the laundering of more than $7 billion. In a statement, the Office of Foreign Assets Control (OFAC), a Treasury Dept.