File:The Code Breakers Library of National Cryptologic Museum (3321040062).jpg

The Codebreakers by David Kahn

Because The Codebreakers dealt with several potentially sensitive subjects, like the National Security Agency, the US Intelligence and defense communities asked to review the manuscript prior to publication. After its review, the Department of Defense stated they "deplored the book" and "it would not be in the national interest to publish it." Kahn deleted certain portions related to NSA and the book was published without further incidence. Source of material : National Cryptologic Museum

The Codebreakers (from Wikipedia article on David Kahn) 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. 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 journalist, was contracted to write a book on cryptology 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 the author James Bamford writing in 1982, the agency attempted to stop its publication, and considered various options, including 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 authorities" and recommended "further low-key actions as possible, but short of legal action, to discourage Mr. Kahn or his prospective publishers". Kahn's publisher, the Macmillan company, handed over the manuscript to the Federal government for review without Kahn's permission on 4 March 1966. Kahn and Macmillan eventually agreed to remove some material from the manuscript, particularly concerning the relationship between the NSA and its British counterpart, the GCHQ.

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. This book was republished in 1996, and this new edition includes an additional chapter briefly covering the events since the original publication.