The Codebreakers comprehensively chronicles the
history of cryptography from ancient Egypt to the time of its writing. It is widely regarded as the best account of the history of cryptography up to its publication. Most of the editing, German translating, and insider contributions were from American World War II cryptographer Bradford Hardie III.
William Crowell, the former deputy director of the National Security Agency, was quoted in
Newsday as saying, "Before he (Kahn) came along, the best you could do was buy an explanatory book that usually was too technical and terribly dull." Kahn, then a newspaper journalist, was contracted to write a book on cryptography in 1961. He began writing it part-time, at one point quitting his regular job to work on it full-time. The book was to include information on the National Security Agency (NSA), and according to author
James Bamford writing in 1982, the agency attempted to stop its publication and considered publishing a negative review of Kahn's work in the press to discredit him. A committee of the United States Intelligence Board concluded that the book was "a possibly valuable support to foreign COMSEC [communications security] authorities" and recommended "further low-key actions as possible, but short of legal action, to discourage Mr. Kahn or his prospective publishers."
The Codebreakers did not cover most of the history concerning the breaking of the German
Enigma machine (which became public knowledge only in the 1970s). Nor did it cover the advent of strong cryptography in the public domain, beginning with the invention of
public key cryptography and the specification of the
Data Encryption Standard in the mid-1970s. An updated edition in 1996 included an additional chapter covering events since the original publication. == Later career ==