David Kahn
He wrote the book the NSA didn't want published — and then wrote six more.
Cryptohistory Biography
David Kahn
David Kahn was a Jewish-American journalist and historian from New York who spent fifteen years researching and writing the first comprehensive history of cryptography from antiquity to the twentieth century. The Codebreakers (1967) ran to 1,164 pages and covered every significant cipher, cryptanalyst, and intelligence episode Kahn could document. Its pre-publication manuscript was reviewed by the NSA, which reportedly asked Macmillan to delay publication on national-security grounds; the publisher declined. The book became a standard reference, sparked a generation of academic and amateur cryptographers, and helped establish cryptologic history as a widely read field.
Why This Person Matters
Kahn's significance is cultural, historiographic, and indirect-technical. By documenting the complete history of cryptography in one accessible volume, he provided both the historical framework and the motivation for the academic explosion in cryptographic research that characterized the 1970s. Martin Hellman cited The Codebreakers as an influence; it also reached readers who would contribute to modern cryptography. The cryptographic revolution of the 1970s — public-key cryptography, DES, academic cryptanalysis — had many causes, but the existence of a widely read, rigorously researched history of the field that showed both its depth and its unsolved problems was among them. Kahn spent his lifetime ensuring that the field's history was not forgotten.
The Codebreakers (Macmillan, 1967; revised 1996) traces cryptography from ancient Egypt through the NSA era. Its coverage of WWII cryptanalysis — written before Bletchley Park was declassified — relied on fragmentary public sources and interviews with veterans who could say little. The 1996 revision incorporated three decades of post-declassification scholarship. As a reference work it remains comprehensive and accurate; as historical writing it is also engaging narrative. Kahn researched primary sources in German military archives, interviewed veterans across Europe, and consulted mathematical papers in multiple languages.
The NSA objected to parts of the pre-publication manuscript. Some material was removed or modified after discussions; the book was not published wholly unchanged. It nevertheless made a large body of cryptologic history available to general readers. The surviving drafts and correspondence are evidence for this more complicated publication history.
Kahn's subsequent books include: Hitler's Spies (1978), a comprehensive study of German military intelligence in WWII; Kahn on Codes (1983), a general-audience introduction; Seizing the Enigma (1991), a detailed account of US and British naval captures of Enigma material; and The Reader of Gentlemen's Mail (2004), a biography of Herbert Yardley. He died in January 2024 at age 93, after a long career documenting a field whose archives continued to open.
| Born | February 7, 1930, Mineola, New York |
| Died | January 23, 2024, the Bronx, New York |
| Education | Bucknell; Oxford (DPhil, St Antony’s College) |
| Major Work | The Codebreakers (1967, 1996 revised) |
| NSA response | Attempted classified review to delay/suppress publication |
| Later works | Hitler's Spies, Seizing the Enigma, The Reader of Gentlemen's Mail |
| Legacy | Defined cryptohistory as a field; inducted NSA Cryptologic Hall of Honor 2009 |