Chris Christensen Northern Kentucky University

Naval Communications Washington, DC

Alfred Clifford MIT (Top, 1) Marshall Hall, Jr. Yale (Middle, 2) Andrew Gleason Harvard (Middle, 5)

Howard Engstrom Yale (Top, 5) Lawrence Steinhardt MIT student (Top, 8)

Howard Campaigne Minnesota (Top, 10) Reed B. Dawson Illinois (Top, 11) William A. Blankinship (Top, 12) William Wray Williams (Bottom, 6) J. J. Eachus Purdue (Middle, 6)

National Cash Register Dayton, OH

2011 Inductee

hatsufrom58743, shuushifufull stop50418 maruship name76833 begin45435 good34131 commander-in-chief41595 radio silence66201

Encipher “Full stop”50418 Additive65358 False sum15766 Transmitted15766 Additive65358 “Full stop”50418 Decipher

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

… we also saw a machine for aiding one in the recovery of subtractor groups when messages have been set in depth. A rather similar machine was made by Letchworth for us in early 1940, and although not nearly so convenient as this model, has been used quite a bit I believe. Alan Turing

DisplayColors

D – B = 15103B = 89172

JN-25

1943 The cryptologic crisis of the Battle of the Atlantic eased, and Lt. Lawrence Steinhardt was assigned the responsibility of designing machines to attack Japanese additive cipher systems.

Align message groups vertically – in depth Align message groups and recovered additives

Copperhead I

Align messages in depth

19 November 1943 Proposal for Copperhead I submitted. 3 November 1944 Copperhead I shipped to NCA.

Align messages and recovered additives

Slide recovered additives along messages, subtract, and check for high frequency code groups.

At least 10 additives. At least 8 scanning groups. At least 5 have confirmed meanings.

20 December 1943 Copperhead II is low priority. 8 November 1944 Copperhead II project is terminated.

?

Hall’s weights Shinn weights

*

Differences of Scanning Groups Distribution of Differences

DifferenceShinn Weights or or or or

*418

Align JN-25 messages in depth

Never Produced.

Align JN-25 messages and recovered additives

Message Additive

12 April 1944 “Mamba Theory.” 18 November 1944 Status of Mamba? Acme Pattern and Tool Company.

1 December 1943 – 1 July 1945 production

1 December 1943 – 1 July Copperhead One1 Parallel Grenade1 Cilli Grenade 10 Vipers1 Mamba8 Inverted Bombes 1 Mike30 Wave FiltersModified 25 Bombes 3 Rattlers60 Boa25 Squelcher Circuits 2 Gypsy-Topas10 Special Boa 1 Double Bombes1 Satyr 1 Asp495 Pluggable Reflectors 2 Sliding Grenades4 Standard Grenades 60 M-91 Drag Grenade 8 M-81 Coast Guard Grenade

It is believed that considerable thought should be given to the desirability of building equipment of general usefulness which might do this and other jobs rather than a number of machines each designed to meet a specific need.

This thought is advanced because it is felt that we should be building for the future where in machines built for specific purposes may become obsolete but the value of a more generally universal machine might become enhanced. J. Howard

Joseph Wenger Howard Engstrom William Norris John Parker ERA