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

[...]

The U.S. government considered the book so volatile that the National Security Agency, the country’s premier cryptology arm, pondered how to block its publication. It even considered breaking into Mr. Kahn’s home in Great Neck, N.Y.

[...]

In a curious twist, in 1993, the N.S.A. invited Mr. Kahn to be its scholar in residence. Despite the agency’s earlier efforts to sideline his work, by the 1990s it had come to respect him for advancing the field of cryptology. In 2020, he was even named to its hall of fame.

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