So, back from a delicious dinner with Gisela😋😋😋
PAt Re:
"It was the Lorenze machine that was cracked with the first electronic computer built by Tommy Flowers .."
Actually the Lorenz machine, a high security teleprinter cipher machine ordered by the German Army, was cracked BY HAND! By a team led by Bill Tutte and without ever seeing the machine until the end of the war!
The Lorenz used obscuring characters to hide the message. An additive system devised by in 1918 by Gilbert Vernam. Example-
Message character is A. Machine adds obscuring character C, transmitted output is F.
At TX: A
C = F, at RX: F C = A and so on.
Brigadier John Tiltman, one of the top codebreakers in Bletchley Park, took a particular interest in these enciphered teleprinter messages. Tiltman knew of the Vernam system and soon identified these messages as being enciphered in the Vernam manner.
Because the Vernam system depended on addition of characters, Tiltman reasoned that if the operators made a mistake and used the same Lorenz machine starts for two messages (a depth), then by adding the two cipher texts together character by character, the obscuring character sequence would disappear. He would then be left with a sequence of characters each of which represented the addition of the two characters in the original German message texts. For two completely different messages it is virtually impossible to assign the correct characters to each message. Just small sections at the start could be derived but not complete messages.
Again German operators helped! Against strict orders they reset their machines to the same start sequence when required to repeat a message which was badly received.
Obscuring characters were generated according to a pseudo random sequence, pseudo implying a repetition period. The repeated message, with some minor changes, short cuts made by the sending operator, gave some clues.
Tutte tried various repetition periods until he found the one setting that decoded the 4000 character message by writing out all the bit patterns of each of the 5 channels (5 bit Baudot code) of the teleprinter.
Then over the next two months Tutte and other members of the Research section worked out the complete logical structure of the cipher machine (Pic 1). Remember; NOT having seen the physical machine.
Post Office Research Labs at Dollis Hill were asked to produce an implementation of the logic worked out by Bill Tutte & Co.
Frank Morrell produced a rack of uniselectors and relays which emulated the logic (Pic 2). It was called "Tunny". So now when the manual code breakers at Bletchley had laboriously worked out the settings used for a particular message, these settings could be plugged up on Tunny and the cipher text read in. But this all took several weeks, by which time the message was stale and useless.
Speeding things up😀
The mathematician Max Newman now came on the scene. He thought that it would be possible to automate some parts of the process for finding the settings used for each message.
He approached TRE at Malvern to design an electronic machine to implement the double-delta method of finding wheel start positions which Bill Tutte had devised. The machine was built at Dollis Hill and was known as Heath Robinson after the cartoonist designer of fantastic machines. There were problems with Heath Robinson keeping two paper tapes synchronised at 1,000 characters per second. One tape had punched on to it the pure Lorenz wheel patterns that the manual code breakers had spent weeks laboriously working out. The other tape was the intercepted enciphered message tape.
THEN-
THIS is where Tommy Flowers came in Pat.
Heath Robinson worked well enough to show that Max Newman's concept was correct. Newman then went to Dollis Hill where he was put in touch with Tommy Flowers, the brilliant Post Office electronics engineer. Flowers went on to design and build Colossus to meet Max Newman's requirements for a machine to speed up the breaking of the Lorenz cipher.
Tommy Flowers' major contribution was to propose that the wheel patterns be generated electronically in ring circuits thus doing away with one paper tape and completely eliminating the synchronisation problem.
Cutting a long story 'sidevays😁'-
Colossus design started in March 1943. By December 1943 all the various circuits were working and the 1,500 valve Mark 1 Colossus was dismantled, shipped up to Bletchley Park, and assembled in F Block over Christmas 1943 (Pic 3). The Mark 1 was operational in January 1944 and successful on its first test against a real enciphered message tape.
Colossus reduced the message decoding time from several weeks to a few hours.
But it did not in itself break the coding system. It effectively used the knowledge gained by hand by Bill Tutte &Co. From first reception of Lorenz messages to fast, operationally useful decoding four years elapsed, 1940-44.
For more info and tech detail see links below.
Cheers All, Doug😎
https://www.codesandciphers.org.uk/lorenz/index.htm
https://www.codesandciphers.org.uk/lorenz/colossus.htm
