For 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.

This company was called Crypto AG, and got its first contract to build code-making machines for U.S. troops during World War II.

The Swiss firm made millions of dollars selling equipment to more than 120 countries well into the 21st century. Its clients included Iran, military juntas in Latin America, nuclear rivals India and Pakistan, and even the Vatican.

But... There is a but. What none of its customers ever knew was that Crypto AG was secretly owned by the CIA in a highly classified partnership with West German intelligence. These spy agencies rigged the company’s devices so they could easily break the codes that countries used to send encrypted messages.

The Washington Post and ZDF, a German public broadcaster, in a joint reporting project were able to disclose the decades-long arrangement, among the most closely guarded secrets of the Cold War.

The account identifies the CIA officers who ran the program and the company executives entrusted to execute it.

The operation, known first by the code name “Thesaurus” and later “Rubicon,” ranks among the most audacious in CIA history.