SOLUTION OF THE LAST OF THE “HMS HURRICANE” INTERCEPTS


By Dan Girard

Image "Enigma message from Kplt Herrmann Rasch"
U106 war diary
After ten years of trying, and innumerable runs of my Bombe-simulator program, I’ve finally broken (with Michael Hörenberg’s generous assistance) the last of the three naval Enigma messages that Ralph Erskine included in his 1995 letter to Cryptologia, and that had been intercepted by H.M.S. Hurricane in 1942. For now, I’ll just give the solution; I’ll explain the method in a later article.

The ciphertext used differs in a few letters from the ciphertext as it appears in Mr. Erskine’s letter. I’ll explain why later.

The message is from Kplt Herrmann Rasch U 106 (1914 - 1974). Read the war diary.



Ciphertext:

HCEYZTCSOPUPPZDICQRDLWXXFACTTJMBRDVCJJMMZRPYIKHZAWGLYXWTMJPQUEFSZBOTVRLALZXWVXTSLFFFAUDQFBWRRYAPSBOWJMKLDUYUPFUQDOWVHAHCDWAUARSWTKOFVOYFPUFHVZFDGGPOOVGRMBPXXZCANKMONFHXPCKHJZBUMXJWXKAUODXZUCVCXPFT

Enigma Machine Settings:

Reflector: B
“Greek” Wheel: Beta
Wheels: 613
Ring Settings: ZZDG
Message Key: NAQL
Plugs: BQ CR DI EJ KW MT OS PX UZ GH

Alternate Ring Settings and Message Key:

Ring Settings: ZZTG
Message Key: NBHL

Plaintext:

BOOTKLARXBEIJSCHNOORBETWAZWOSIBENXNOVXSECHSNULCBMXPROVIANTBISZWONULXDEZXBENOETIGEGLMESERYNOCHVIEFKLHRXSTEHEMARQUBRUNOBRUNFZWOFUHFXLAGWWIEJKCHAEFERJXNNTWWWFUNFYEINSFUNFMBSTEIGENDYGUTESIWXDVVVJRASCH

Plaintext with word divisions, and with garbled letters corrected:

BOOT KLAR X BEI J SCHNOOR J ETWA ZWO SIBEN X NOV X SECHS NUL CBM X PROVIANT BIS ZWO NUL X DEZ X BENOETIGE GLAESER Y NOCH VIER KLAR X STEHE MARQU BRUNO BRUNO ZWO FUNF X LAGE WIE J SCHAEFER J X NNN WWW FUNF Y EINS FUNF MB STEIGEND Y GUTE SICHT VVV J RASCH

Formatted German plaintext:

Boot klar. Bei “Schnoor” etwa 27. Nov. 60 cbm. Proviant bis 20 Dez. Benötige Gläser, noch 4 klar. Stehe Marqu. BB 25. Lage wie “Schaefer”. NW 5, 15 mb steigend, gute Sicht. Von “Rasch”.

English translation (words in square brackets added to make the meaning more clear):

Boat clear. [Will rendezvous] at Schnoor about 27 November. 60 cubic meters [fuel oil remaining], provisions [sufficient] until 20 December. Need binoculars; [only] four now serviceable. Am at naval square BB 25. Situation like Schaefer’s. [Wind] northwest [force] 5, [atmospheric pressure] 15 millibars rising, good visibility. From Rasch.

Note 1: U-boats were usually referred to in radio messages by their commanders’ names. “Schnoor” was the commander of the fuel-tanker submarine U-460, “Rasch” was the commander of U-106, which had been ordered to rendezvous at U-460’s position for refueling, and “Schaefer” was the commander of U-183, which had been operating in the same general area as U-106.

Note 2: The position given, naval square BB 25 (approximately 49°41'N , 58°34'W), is an error, probably on the part of the radio operator who prepared the message. The boat’s actual position was CB 25 (approximately 41°35'N, 62°28'W). The two positions are more than 500 nautical miles apart.