Crack the Code!

This message was sent by the Chinese embassy to North Korea, and was intercepted by the US Navy, operating a listening post atop the superstructure of a destroyer in the Sea of Japan. The message probably contains the phrase "North Korea" and/or "North Koreans."

Good luck!

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Frequency Distribution of Ciphertext

 

Frequency Distribution of English

A joint project of Brendan Bard, Prof. Gregory Bard, and Prof. Seth Dutter, University of Wisconsin---Stout (January 30th, 2019)