or more than half a century, governments all over the world trusted a single company to keep the communications of their spies, soldiers and diplomats secret. The company, Crypto AG, got its first break with a contract to build code-making machines for U.S. troops during World War II. Flush with cash, it became a dominant maker of encryption devices for decades, navigating waves of technology from mechanical gears to electronic circuits and, finally, silicon chips and software. The Swiss firm made millions of dollars selling equipment to more than 120 countries well into the 21st century. Its clients included Iran,...