David Kahn, leading historian of codes and code breaking, dies at 93

David Kahn, whose 1967 book “The Codebreakers” made him the world's foremost authority on cryptology (the science of making and breaking secret codes), died Jan. 24 in the Bronx. He was 93.

His son Michael said the death in a care home was the result of the long-term effects of a stroke in 2015.

Before Mr. Kahn's book, cryptology itself was something of a secret. Despite an explosion of cryptological technology and techniques in the twentieth century and the central role they played during World War II, this topic has generally been overlooked by historians, if only because their possible sources were still highly classified.

“Code deciphering is the most important form of secret intelligence in the world today,” Mr. Kahn wrote in the foreword to his book. “Yet it never had a chronicler.”

Over the course of more than 1,000 pages, along with some 150 pages of notes, Mr. Kahn explained the long history of cryptology, beginning with ancient Egypt 4,000 years ago and continuing through the French and American revolutions, the innovations that were brought about by the advent of cryptology. telegraph and telephone until the mid-20th century and the beginning of computer-aided code breaking.

The US government considered the book so ephemeral that the National Security Agency, the country's top cryptology arm, considered how to block its publication. Consideration was even given to breaking into Mr. Kahn's home in Great Neck, NY

Ultimately, the agency opted for more overt means and demanded that the publisher, Macmillan, not release it. The company refused; instead, MacMillan and Mr. Kahn submitted the text to the Defense Department for review. Mr. Kahn agreed to cut a few paragraphs about Britain's code-breaking efforts during World War II, which were still classified, but otherwise kept the book intact.

Despite its weight and then-mysterious subject matter, 'The Codebreakers' was a hit. It sold about 75,000 hardcover copies, earned Mr. Kahn an appearance on “The Tonight Show” and introduced countless readers to the subject.

It also inspired a growing community of private sector cryptologists who had previously been stymied by federal authorities. Until the late 1960s, anyone who filed a patent on a cryptological device or technique was visited by an agent; the government would even go so far as to hire such inventors – simply to gain control over their intellectual property.

“There was so little available about cryptography,” Steven Levy, the author of “Crypto: How the Code Rebels Beat the Government Saving Privacy in the Digital Age” (2001), said in an interview. “And once you got past the children's books on how to use a wheel, decoder rings and things like that, the serious work was classified.”

But as Mr. Kahn argued in his book and elsewhere, cryptology had to be free; the coming digital communications revolution and the need to keep such communications secure required this. By providing a detailed map of where cryptology had been, he motivated aspiring coders to go further — Mr. Kahn's book, Mr. Levy said, was “their Bible.”

David Kahn was born on February 7, 1930 in Manhattan and grew up in Great Neck, on the north shore of Long Island. His mother, Florence (Abraham) Kahn, owned a glass factory and his father, Jesse Kahn, was a trial attorney.

A chance encounter sparked David's interest in codes. When he was a teenager, he discovered a book in the Great Neck Public Library: Fletcher Pratt's “Secret and Urgent” (1939), a history of secret codes filled with the kind of cloak-and-dagger intrigue that sets a heart passionate about racing.

“It got me hooked – and I never grew up,” he told The Washington Post in 1978.

Mr. Kahn received a bachelor's degree in social sciences from Bucknell University in 1951 and then went to work as a reporter for Newsday on Long Island.

Cryptology remained a side issue until 1960, when he wrote an article for The New York Times Magazine on the history of the subject, inspired by the defection of two National Security Agency employees to the Soviet Union; they took with them a treasure trove of American code-breaking secrets.

The story sparked public interest at the NSA and earned Mr. Kahn the book contract that resulted in “The Codebreakers.” He left Newsday to write it, then moved to a job as an editor at The International Herald Tribune in Paris.

His marriage to Susanne Fiedler in 1969 ended in divorce in 1994. Together with his son Michael, he is survived by another son, Oliver.

While in Europe, Mr. Kahn obtained his doctorate in modern German history at Oxford, where he studied under the eminent English historian Hugh Trevor-Roper.

His dissertation, entitled 'Hitler's Spies: German Military Intelligence in World War II', was published in book form in 1978.

The book, based in part on extensive interviews with former high-ranking Nazi officials, showed that Germany's intelligence apparatus had lagged woefully behind that of Britain and the United States, and as a result had led the country to commit strategic blunders – including the failure to foresee the Allied invasion of Italy and the assumption that the D-Day landings were a distraction.

Mr. Kahn later returned to Newsday as an editor, but he continued to write about codes. In addition to a number of books, he founded the first scientific journal on the subject, Cryptologia, which he also edited.

In a curious twist, the NSA invited Mr. Kahn as a scientist in residence in 1993. Despite the agency's previous attempts to sideline his work, by the 1990s it had come to respect him for advancing the field of cryptology. In 2020 he was right named after its hall of fame.

“A journalist, scientist and author with a career spanning more than half a century,” the agency said, “Dr. David Kahn has done more than any individual to educate the public around the world about the importance of cryptology to international peace and security.”