JN25: The Imperial Japanese Navy's Primary World War II Naval Cipher | Virtual Talk

A Virtual Talk by Professor Chris Christensen
A successor to the Red Book and Blue Book codes, JN-25 was introduced by the Imperial Japanese Navy on 1 June 1939.
JN-25 was a 5-digit code that was enciphered by additives. The cipher was first broken by British codebreaker John Tiltman, but after the Japanese attacks that led to war in the Far East, the primary responsibility for breaking JN-25 messages was assigned to the US Navy’s codebreaking section OP-20-G.
This presentation will explore the structure and evolution of the cipher and describe the basic ideas of the codebreaking attacks on JN-25.
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[@d3ntr0x]

Thank you very much for the detailed explanation of the mechanisms behind the JN-25. It illustrates very well the level of attention and resources assigned to intelligence tasks that the competing powers had during WWII.

[@Petertronic]

Excellent talk, so interesting, I learnt a lot.

[@proudsnowtiger]

Fascinating lecture and a good presenter, but the white text on grey background is too low-contrast for my tired old eyes. I appreciate that was the choice of the speaker; perhaps you could come up with some accessibility guidelines to give to future contributors?

[@crystalskullsucked]

This was an amazing presentation- gosh I wish I was smarter to understand some parts of this though

[@SusiesRepeat]

This shows the truly brilliant minds that must have been needed to break these codes. Way above my intelligence.

[@jaanlepnurm]

I thought Japanese language would be cypher enough.