The Black Chamber typically refers to an American organization[0] although, to be fair, it was not the only use. > The term "Black Chamber" predates Yardley's

The Black Chamber typically refers to an American organization[0] although, to be fair, it was not the only use. > The term "Black Chamber" predates Yardley's use of it in the title of his book. Codes and code breakers have been used throughout history, notably by Sir Francis Walsingham in Elizabethan England. A so-called cabinet noir was established by King Henry IV of France in 1590 as part of the Poste aux Lettres. [0]: https://en.wikipedia.org/wiki/Black_chamber https://en.wikipedia.org/wiki/Black_chamber