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Summary

This is the ciphertext of the first part of the 14-part message which was delivered by the Japanese to the US Government on December 7, 1941. The source of the original document is: NARA. RG457 NSA Historical Cryptographic Collection. Copies of Messages 901, 902, 907 and 910 from Tokyo to Wash On 6 and 7 Dec 41 . NR. 1815, Box 738.

Note the hand-written calculations at the upper right which deduce the initial positions of the stepping switches and the stepping order from the message indicator. First the additive for the month of December 1941 is subtracted, then the digits are rearranged according to the deduced transposition. The resulting number determines the starting positions, 9 for the sixes and 1, 24, 6 for the twenties, and the stepping order as number 4, which corresponds to 231.

Licensing

This article or image contains materials that originally came from a National Security Agency (NSA) website or publication. It is believed that this information is not classified , and is in the public domain in the United States. See the privacy and security information.

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