I have kept this U.S. Signal Corps story bottled up for 47 years, but now it's obvious to me that modern cryptographic techniques have rendered these secrets "moot", or maybe even obsolete.
A code is a secret substitution of words for words. For example, the word GOAT may be secretly agreed upon to stand for the word TOWN as in this message: "The GOAT is now surrounded."
A cipher, on the other hand, is much more complex, as it is the secret substitution of letters for letters. The five-letter group RWEMP may stand for the five-letter word SQUAD, as in this message: "Send bomb RWEMP to defuse the object."
Well, in W.W.II, the main Allied cipher machine was called the SIGABA. This super-secret word-letter scrambler was used throughout the European and Pacific Theaters of Operaton. All U.S. British, Canadian, ?u??c, and French Commands had them at Army, Corps, and Division Headquarters, and they were also part of the secret communications ssystems for the Air Forces and Navies. Ships at sea above the level of destroyers all had SIGABAs.
It was a massive, electric typewriter with four big ROTORs, or wheels, in its innards instead of keys with typefaces. Each ROTOR had the entire English alphabet on its rim, in type face. At midnight each night the four ROTORs were changed around in accordance with dated documents kept in a safe beneat the monstrous machine. It is mathematically ridiculous to try to figure the odds against the enemy (German or Japanese) behing able to match the changing arrangement of the alphabet thus set secretly, times four (x4) I know that this system was securely maintained throughout W.W.II, ??? we continued to use it in the Army? of Occupation.
But our security efforts were very demanding. We had our Code Rooms in places like old bathrooms, with only one door. There was an armed guard at that door 24 hours a day. We carried magnesium bombs to destroy all equipment and documents in case of imminent capture. These bombs were so hot that if you pulled the pin, the light would be blinding, and they would quickly burn their way through the steel safes, through the machines, through the documents, and on through the floor beneath. We, of course, were supposed to die fighting for our sacred, secret stuff!
The SIGABA machine worked like magic. You would be confronted by pages of five-letter "?mish-?mash" that came in by radio, teletype, telephone, pigeons, plane, jeep, or foot messenger that looked like this: RWEMP FXQRE GLAUN FJALZ VHOYI JWBZK--and on and on, pages of it. If you had your SIGABA set up right--and the guy at the other end (the sender) did too--you typed what you saw, and you got cleartext like: "20th DIVISION REPORTS HEAVY ARTILLERY RESISTANCE AT THE VILLAGE OF BITCHE" (Neat, huh?)
The Allied line-up for the Battle of the Rhineland in the winter of 1944-1945 looked like this, from south to north: ?First French Army (General de Lattre de Tassigny); U.S. Seventh Army--our outfit--(General Alexander Patch); U.S. Third Army (General George Patton); British, Canadian, ?Iuzoc? Armies (General Bernard Montgomery).
The most hazardous time for the security of our code-cipher ?mysteries? was when we were on the move, and a "?Jeep Train" with all this equipment had to move forward to a new Command Post. (Some of my current back problems are due to the strain of having to lift these heavy safes on and off our trucks) Well, it was a fast-moving war. In Alsace-Lorraine alone, I remember these locations and having to establish a new Code Room at each: Nancy, Baccarat, Ribeauville, M??h??ge, S???qu??i??es, Ste Marie aux Mines, and Colmar. We were often driving and working in slush and snow.
Now, the French, on our right, in the Vosges Mts. had some Algerian troops with them--fierce fighters, very spirited, but also often quite undisciplined. Well, on one such move, the First French Army reluctantly reported that a Code Truck, with a SIGABA aboard, had simply disappeared!
All Hell broke loose! The secret code systems of all Allied
Forces--land, sea, and air, world-wide--had been compromised.
We had to abandon use of our magic machine and resort to slow, laborious
manual code techniques, one of which called "STRIPS" was a
bit like crossword puzzles. The whole war ground to a screeching
halt because of delay or failure of communications.
We never heard an official version. (The French were just too embarassed), but the story goes that the French "Jump Team" of two Signal people had briefly left this vehicle unguarded to attend to some distraction: Food? Drink? A "call of nature"??? Sex???? Who knows????? And a couple of Algerians, no doubt drunk, saw a golden opportunity to go for a joy ride. When they sobered up enough to realize they had a ?cargo "too hot to handle," they simply ran the truck off a bridge! (a la Chappaquiddick?)