1919: The American "Black Chamber" began operations.
The following is an excerpt from NSA Web page: Pearl Harbor Review - The Black Chamber. To read more, follow the link at the end of the page.
The sponsor for the Cipher Bureau was the State Department, although the Army and the Navy shared in the budgeting and decrypts. Herbert Yardley, formerly a code clerk for the Department of State, recently a major in command of MI-8, Military Intelligence's wartime cryptologic section, was chosen as head of the new civilian organization. The Cipher Bureau had the distinction of being the first national, civilian intelligence organization in peacetime.
After the Bureau was dissolved in 1929 and Yardley was out of work, he decided to write his story - eventually in the form of a book, "The American Black Chamber." The book was filled with good stories well told, as well as frank descriptions of Yardley's successes in cryptanalysis. It was a best-seller in 1932 -- overseas as well as domestically.
While many of his former colleagues and those now engaged in military cryptanalysis were appalled at the revelations in his book, Yardley defended his publication. He claimed self-righteously that his only motive had been to alert the United States to the weakness of its own systems and to the power of cryptanalysts. What he could do, he said, people in other nations could also do.