» From Fish to Colossus: How the German Lorenz Cipher was Broken at Bletchley Park

From Fish to Colossus: How the German Lorenz Cipher was Broken at Bletchley Park Reviews

Customer Rating:
Summary: The definitive book on Colossus
Comment: It is an indictment of the unnecessary over-zealous British penchant for secrecy that arguably the most important tool ever invented, and prime mover of the consequent information technology revolution - the computer - and its first incarnation Colossus, was kept secret by the British until 1996 when American declassified documents became available, whereby the story of high-level machine codebreaking at Bletchley Park could be pieced together and the importance of Colossus in this history became apparent for the first time in the public domain.

The story of Enigma and Bletchely Park is now well-known and widely reported, (which was also suppressed by the British establishment for far too long), but the more important German teleprinter ciphers of the highest security level were of several orders more complex. The massive information manipulation techniques required to process the decrypting of these ciphers spawned the computer age in the first electronic machines such as 'Robinson' and 'Colossus'. This led inevitably to the development after the war in university mathematical departments of increasingly more sophisticated computers and of course what later became the computer industry as soon as commercial machines were practicable and economically viable. That is a story in its own right.

More amazing to me, was the continued resistance of the British establishment to Tony Sale in his determination to re-create a working facsimile of Colossus at Bletchley museum when the secret was out, and his having to overcome great odds to do this, and having to use information provided by American documents, as well as the snippets of memories of some of the very few people still available who worked on Colossus.

It appears to me the Americans are (rightly) very proud of their role in the history of WW2 cryptography and of early computing, and are willing to disseminate the information, whereas the British establishment have had to have it winkled-out painfully and grudgingly very late in the day.
I have a technical computer book published in 1969 for example extolling the virtues of the "first computer" ENIAC in 1946, and of the guiding American mathematician behind it Von Neumann, without any reference to Colossus (first operational in January 1944) or of Alan Turing.

This book 'From Fish to Colossus' is the definitive and best technical treatise available on the breaking of the German Lorenz machine teleprinter cipher (code named 'Fish' by the British), and contains information about other associated machines for similar purposes at the time. It is effectively a collection of all the material available to date (mostly American sources and from Tony Sale) about Colossus and of the mathematical treatment that made it possible.
The mathematical content will of course be difficult for none mathematicians, but there is plenty of historical material, and some which will please the electronics-minded with some circuit diagrams included. I have a particular interest in cryptography and have followed the story as closely as possible, yet found a lot in this booklet which I had not seen before.
It is an absolute must for anyone interested in the technical aspects of the Colossus story.

My only regret is that although it is primarily a great story of brilliant British innovation at its best, it has not sprung from a British author and is based on mainly American source material. The author Harvey G. Cragon of Dallas Texas is to be congratulated on putting this excellent book together for us.

Douglas Denny. BSc.(Hons)
Bosham. England.

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Customer Rating:
Summary: Excellent, for what it does
Comment: I purchased both this book and Jack Copeland's "Colossus: The Secrets of Bletchley Park's Code-breaking Computers" at the same time, and I'm glad to have done so. Copeland's book provides information on many of the personalities and contains sections by some of the individuals who made the breakthroughs, but this book contains more details of the mathematics and is easier to understand. (I also recommend Frank Carter's pamphlets sold by Bletchley Park, which seem to be currently unavailable.)

The breaking of the German Lorenz cipher radioteletype is fundamentally different from the breaking of the Enigmas in that statistical methods are of greater importance and the rotor wiring of a Turing-Welchman Bombe performs a much more complex logical operation at each step than the logical operations possible on the Heath Robinson and Colossus. With a correct crib, only a few possibilities for the rotor order and starting position show up on a Bombe. The Heath Robinson and Colossus breaking depend on correlations in two letter combinations of German military text and these correlations survive (slightly) the modulo-two addition of the psuedo-random cipher text. For this reason, short Enigma messages can be broken, but only much longer Lorenz messages (fortunately, the messages were used for army group level communications and the messages tended to be long). As with Enigma, it took some pretty egregious mistakes by operators to cause the initial breakins by analysts. Cragon carefully leads the reader step-by-step through the logic of breaking the codes, with short examples worked out in full. If you want to understand just how it was done, read this book.

This book also contains many of the details of the circuitry on the Heath Robinsons and Colossi, though some of the schematics are poorly printed (the crucial thyratron ring in Figure 8.14 is unreadable), as are most of the half-tone photographs.

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Customer Rating:
Summary: Very interesting, well researched, quite technical
Comment: This pamphlet is very thoroughly researched and contains the details of how the cipher machine worked and how the cipher was broken, from hand methods up to Colossus. If you are not used to thinking about binary logic then the details of the decryption might be very difficult to understand. However the content is fascinating because it reveals the very first stages in the development of the computer: from mechanical, through relays, then valves, all in a few years, but not yet quite with the idea of the stored program (the program was set by using switches and plugs, hard-coding the machine for each task). It even includes some circuit diagrams, though it doesn't matter if you can't understand them (if you can, they're fascinating, honest!) The pamphlet is obviously self-published and in places could do with some review.

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