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The Navy’s Attack on JN-25

The Navy’s Attack on JN-25. Chris Christensen Department of Mathematics and Statistics Northern Kentucky University. OP-20-GM. NCML. US Navy Cryptologic Bombe. Lawrence Steinhardt. JN-25. 1 June 1939. Message. 67854 59199 76833 57699 10047 70863 06138 27924 All “scan.”.

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The Navy’s Attack on JN-25

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  1. The Navy’s Attack on JN-25 Chris Christensen Department of Mathematics and Statistics Northern Kentucky University

  2. OP-20-GM NCML

  3. US Navy Cryptologic Bombe

  4. Lawrence Steinhardt

  5. JN-25 1 June 1939

  6. Message 67854 59199 76833 57699 10047 70863 06138 27924 All “scan.”

  7. Table of Additives

  8. Encipher 67854 59199 76833 57699 10047 70863 06138 27924 48677 26777 66476 09369 47063 29174 67495 14631 05421 75866 32209 56958 57000 99937 63523 31555

  9. JN-11 1 March 1943

  10. Indicators and Depth

  11. 1 December 1943

  12. Copperhead I Aligning Messages in Depth

  13. Double Repeats 05661 06511 07465 07495 12143 14240 14963 18673 78009 57047 79519 06511 90318 72216 12143 94860 70240 05661 06511 07465 07495 12143 14240 14963 18673 40876 06511 90318 72216 12134 94860 70240 54911 32814

  14. Copperhead I

  15. Copperhead I Timetable • 6 December 1943 CH I proposal approved. • 31 January 1944 NCML requested to build CH I. • 1 August 1944 JN-11 became a general purpose cipher. • 25/26 August 1944 how to use CH I on 4-digit ciphers – will install a switch. • 3 November 1944 CH I shipped to Washington. • 5 Copperhead I’s.

  16. Copperhead V Aligning Messages in Depth Using Scanning

  17. Marshall Hall, Jr. (Codegroup 1 + Additive) (Codegroup 2 + Additive) Codegroup 1 – Codegroup 2

  18. Hall’s Weights 10874 96807 20360 07131 11248 44860 19374 97405 03289 35158 01169 01367 01249 11279 513 425 440 515 Mean = 473.25

  19. Shinn Weights 0 0 1 2 6 2 10874 96807 20360 07131 11248 44860 4 5 2 2 19374 97405 03289 35158 7 7 4 0 418 418 365 438 Mean = 409.75

  20. Copperhead V Timetable • 20 December 1943 CH I and CH V mentioned. • 31 January 1944 NCML requested to build CH I and CH V. • 25 July 1944 JN-25 dropped scanning. • Work on CH V stopped.

  21. More Copperheads Copperhead III Copperhead IV

  22. ?

  23. Aligning Messages Against Additives 29720 94370 13723 90122 10983 92197 10951 19298 82306 98130 88929 70898 63750 21452 92715 73079 39653 19374 97405 03289 35158 34380 49054 33416 45139 93655 27740 51535 90688 81108 16959 34255 77661 10874 96807 20360 07131 11248 44860 24894 25385 38000 50955 96199 30366 53758 94993 44165 93766 95469 93389 65986 32194 59861 16664 41540 07255 58798 49815 91541 52762 41057

  24. Copperhead II Aligning Messages Against Additives

  25. Copperhead II 68377 35159 31043 47671 50280 80284 55463 10816 86060 90082 59335 93992 59199 57699 06138 27924

  26. Copperhead II Timetable • 20 December 1943 Copperhead II is low priority and little has been done on it. • 9 November 1944 Copperhead II project was terminated.

  27. Mamba Aligning Messages Against Recovered Additives Using Scanning

  28. Mamba Message 5 6 8 4 6 9 3 5 49073 38472 91259 86989 38094 38898 66585 89960 Additive 5 4 0 6 4 4 4 9 82229 89383 25426 39390 28057 68035 60457 62046

  29. 26 March – 25 April 1944 Mamba Problem

  30. Mamba Timetable • 1 April 1944 JN-11 dropped error detection. • 2 May 1944 build Mamba. • 3 May 1944 high-speed Mamba for JN-11 not required. • 25 July 1944 JN-25 dropped scanning. RU channel uses Love ciphers, which still scanned. • 25 September 1944 Mamba needed in Washington. • November/December 1944 Mamba at Washington. • 1 Mamba.

  31. Mamba

  32. 3 April 1944 John Howard … 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.

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