Chris Christensen Department of Mathematics and Statistics Northern Kentucky University

Encipher U.S. Navy24396 Additive65358 False sum89644 Transmitted89644 Additive65358 U.S. Navy24396 Decipher

Marshall Hall. Jr.

(Codegroup 1 + Additive) (Codegroup 2 + Additive) Codegroup 1 – Codegroup 2

Mean =

Marshall Hall devised [Halls weights] at a time when the indicator system had been broken, but just in case …. Its time did come when the Japanese introduced bigram ordinates to specify additive starting points in December Edward Simpson

30 November 1943 Tentative Method for the Alignment of JN-25 Traffic Without Use of Code or Keys. Lawrance Shinn Ray C. Hackman

My initial reaction to it was to wonder why anyone would go down that road. Collapsing five-figure groups into mod 10 sums of their digits loses an awful lot of information.

Differences of Scanning Groups Distribution of Differences

DifferenceShinn Weights or or or or

Mean =

Copperhead V Cancelled after 25 July Mamba