The Washington Post said that for more than 50 years 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 US 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, military juntas in Latin America, nuclear rivals India and Pakistan, and the Vatican.

But apparently 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 decades-long arrangement, among the most closely guarded secrets of the Cold War, is laid bare in a classified, comprehensive CIA history of the operation obtained by The Washington Post.

The account identifies the CIA officers who ran the programme and the company executives entrusted to execute it. It traces the origin of the venture as well as the internal conflicts that nearly derailed it.

It describes how the United States and its allies exploited other nations' gullibility for years, taking their money and stealing their secrets. The operation, known first by the code name "Thesaurus" and later "Rubicon," ranks among the most audacious in CIA history.