Bletchley Park’s work on JN-25

2025/11/21 by Chris Christensen · 1 voice
Computer Science · Mathematics · Physics and Astronomy · #History and Developments in Astronomy #History and Theory of Mathematics #History of Computing Technologies

paper · doi:10.1080/01611194.2025.2547612

openalex publication_date 2025/11/21 · openalex created_date 2025/11/23 · openalex updated_date 2026/06/13

Abstract

This article describes the work done by codebreakers in the Naval Section at Bletchley Park on the primary World War II Japanese naval cipher JN-25. It also describes the relationship between the US Navy’s OP-20-G and Bletchley Park’s JN-25 codebreakers. To put the work at Bletchley Park into context, the initial breaks into JN-25, the changes to JN-25, the formal agreements between OP-20-G and the Government Code and Cypher School, and various techniques that used differencing of additive-enciphered code are described in detail. In many cases, the story is told using the words of the World War II codebreakers.

Discussions

• It should be noted that, in addition to the US and Great Britain, the Australians and the Dutch also worked on JN-25. doi.org/10.1080/0161... [bsky, 4 points, 0 comments]

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