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Colossus: The Secrets of Bletchley Park's Codebreaking Computers

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The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years. Colossus was built during the Second World War at the Government Code and Cypher The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years. Colossus was built during the Second World War at the Government Code and Cypher School at Bletchley Park. Until very recently, much about the Colossus machine was shrouded in secrecy, largely because the code-breaking algorithms that were employed during World War II remained in use by the British security services until a short time ago. In addition, the United States has recently declassified a considerable volume of wartime documents relating to Colossus. Jack Copeland has brought together memoirs of veterans of Bletchley Park--the top-secret headquarters of Britain's secret service--and others who draw on the wealth of declassified information to illuminate the crucial role Colossus played during World War II. Included here are pieces by the former WRENS who actually worked the machine, the scientist who pioneered the use of vacuum tubes in data processing, and leading authorities on code-breaking and computer science. A must read for anyone curious about code-breaking or World War II espionage, Colossus offers a fascinating insider's account of the world first giant computer, the great great grandfather of the massive computers used today by the CIA and the National Security Agency.


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The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years. Colossus was built during the Second World War at the Government Code and Cypher The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years. Colossus was built during the Second World War at the Government Code and Cypher School at Bletchley Park. Until very recently, much about the Colossus machine was shrouded in secrecy, largely because the code-breaking algorithms that were employed during World War II remained in use by the British security services until a short time ago. In addition, the United States has recently declassified a considerable volume of wartime documents relating to Colossus. Jack Copeland has brought together memoirs of veterans of Bletchley Park--the top-secret headquarters of Britain's secret service--and others who draw on the wealth of declassified information to illuminate the crucial role Colossus played during World War II. Included here are pieces by the former WRENS who actually worked the machine, the scientist who pioneered the use of vacuum tubes in data processing, and leading authorities on code-breaking and computer science. A must read for anyone curious about code-breaking or World War II espionage, Colossus offers a fascinating insider's account of the world first giant computer, the great great grandfather of the massive computers used today by the CIA and the National Security Agency.

30 review for Colossus: The Secrets of Bletchley Park's Codebreaking Computers

  1. 5 out of 5

    J_BlueFlower

    The book is more like collection of articles on the subject. Many authors have written a bit, a few pages, a chapter,... and the result is the XOR operation is explain at least 30 times. The overall impression is a bit messy, and some subjects like limitations are treated in a three page long appendix. If you are fascinated by code-breaking at least read Simon Singh: The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography before this one. However if you are interested in The book is more like collection of articles on the subject. Many authors have written a bit, a few pages, a chapter,... and the result is the XOR operation is explain at least 30 times. The overall impression is a bit messy, and some subjects like limitations are treated in a three page long appendix. If you are fascinated by code-breaking at least read Simon Singh: The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography before this one. However if you are interested in another aspect of code-breaking during WWII than the Enigma, this is the book.

  2. 5 out of 5

    William Bies

    The success of British intelligence in cracking the Enigma code during the second world war and its crucial role in helping the Allies to win the war has, by now, filtered into the consciousness of today’s popular culture. What is not so well known is that the Enigma machine was a commonly available commercial product, sold for use by business as well as by the military during the interwar decades. The Nazi high command was well aware of Enigma’s potential vulnerability and commissioned its elit The success of British intelligence in cracking the Enigma code during the second world war and its crucial role in helping the Allies to win the war has, by now, filtered into the consciousness of today’s popular culture. What is not so well known is that the Enigma machine was a commonly available commercial product, sold for use by business as well as by the military during the interwar decades. The Nazi high command was well aware of Enigma’s potential vulnerability and commissioned its elite cryptographers and engineers to design and implement a far more powerful encryption scheme, known as Tunny. What is amazing is that British intelligence managed to break the Tunny code in addition to the Enigma code, ultimately through the construction of the Colossus, the earliest functioning example of an almost but not quite all-purpose electronic computer (not the same machine as the so-called Bombe designed by Alan Turing to break Enigma, but an even more advanced device). B. Jack Copeland, an historian and director of the Turing archive for the history of computing, along with others tells at last the story of the Colossus in Colossus: The secrets of Bletchley Park’s codebreaking computers, first published in 2006 by the Oxford University Press and based upon information declassified as recently as the first decade of the twenty-first century. Plan of the work: not a continuous narrative, but collection of some 26 short chapters arranged in six parts, supplemented by twelve technical appendices, covering in Parts 1-2 a history of cryptography since Julius Caesar’s Gallic wars, the establishment of Bletchley Park, a description of the Tunny machine and its evolution from Enigma, a timeline of the building and operation of Colossus and then in Parts 3-6 individual treatments of the sections run by Max Newman, Ralph Tester and Thomas Flowers, who were the principal team leaders at Bletchley Park. A large cast of characters contributed in various roles and recollections from many of them form several of the chapters: for instance, the mathematicians Peter Hilton, Jack Good and Gil Hayward; WRNS [Women’s Royal Naval Service] and ATS [Auxiliary Territorial Service] members Catherine Caughey, Helen Currie, Dorothy Du Boisson and Eleanor Ireland and engineers David Bolam, Harry Fensom and Ken Meyers. The remainder of the chapters are filled out with essays from modern experts in computing and cryptography as well as historians of technology. Their contributions are fairly helpful in giving perspective on the significance of the work on Colossus for post-war developments in the computer industry and such things. Copeland and his coauthors go into about as much technical depth as a general reader could wish for in describing how the Tunny code functions, illustrated by means of numerous worked examples. They skimp somewhat, nevertheless, on the mathematical theory behind the statistical technique of the actual algorithm employed by Colossus. Here is what this reviewer has extracted from their account, in his terms, not in the language of the authors: roughly speaking, given a large enough sample of text in a natural language, one can estimate the sampling frequency distribution of the letters of the alphabet contained in it. Now the population frequency distribution is characteristic of the language in question; for instance, in English ‘e’ is the most frequently appearing letter, followed by ‘t’ etc. Thus, if one has a guess as to the cipher, one can generate the putative clear text from it and compute its relative frequency distribution. If the guess is wrong, the result should be nonsense and the computed frequency distribution of letters in it should bear no relation to the population frequency distribution in natural language text, but if one’s guess is right, the result will be meaningful text and its sampling distribution should agree with that of the population known in advance. Therefore, if one tries out a large number of guesses for the cipher, the correct one should stand out like a sore thumb upon performing, say, a chi-squared test. A few complications intervene in the actual scenario the cryptanalysts faced with Tunny: the texts were not written in natural German but in a language laden with military terminology, there were in addition a few special characters and, most important, even with the speed-up afforded by means of electronic computation, it was not realistic to try out every possible setting due to the immense combinatorics involved. Also, errors in transmission due to bad weather could lead to corrupted cipher text, which rendered many intercepts useless. In practice, then, some pre-analysis was required to provide the operators with shrewd priors on what the wheel settings for a given intercept in fact would be. Fortunately, the analysts at Bletchley Park could often take advantage of lapses on the part of the German radio operators. These were labeled as ‘depths’. Sometimes they would forget to dial in the new settings, or commit the serious mistake of transmitting two successive messages based on the same setting and so on. In the latter case, one could take the difference between the two and, with some cleverness and insight based upon knowledge of German vocabulary, work out good guesses for some of the wheel settings. Copeland and his coauthors go into a fair amount of detail on this. The process of decoding intercepts became more challenging as time wore on as the German high command kept raising the bar on its security procedures, such as by publishing a new code on a weekly rather than monthly basis (ultimately, on a daily basis). It is clear that the whole decryption effort would have faltered had it not been for a certain laxness in the early period of deployment of Tunny; if say, the German cryptographers had undertaken steps to identify and avoid such vulnerabilities in the first place – but the German high commanders were guilty of hubris; one is reported to have exclaimed on this very point, ‘But we’re winning the war anyway, aren’t we?’ Copeland does not have very much to say about how knowledge derived from the successful decryptions affected the course of the war – nor could he, given that most of the relevant materials have later been obliterated to protect the secrecy of the operation. Yet, he does describe one case thoroughly: he reproduces the clear text of a message sent on April 25, 1943 outlining the disposition of German forces for the upcoming so-called Zitadelle operation, which was Hitler’s last attempt to gain a breakthrough on the eastern front in southern Russia (rather like the Battle of the Bulge on the western front in the winter of 1944-1945). The failure of this campaign in July 1943, certainly largely to be attributed to the Russians’ possession of superior intelligence, was responsible for turning the tide of the entire war. This reviewer wishes not to dilate any further on the contents of the present book – in any event, the interested reader can gain a sense of the flavor of the history, in all its aspects (technical, personnel-related, human interest and such), only by going through the work in full. For it is replete with telling incidental observations not just by Copeland himself but also on the part of numerous others, including retrospective accounts by most of the principal actors. Rather, let us suggest a few themes one might be prompted to ponder upon finishing a study of Copeland’s commendable achievement in recreating a large part of the whole story of Bletchley Park. First, one can wonder about what one has learnt about codebreaking in general. The Colossus’ method of analysis is based completely on unigrams; what could one do given knowledge of bigrams etc., or perhaps with modern techniques of natural language processing? The spies at the NSA (which forms the single largest employer of trained mathematicians in the country) must be almost unimaginably far ahead of the rest of us on this score! Second, one could deliberate on the effectiveness of the secrecy protocols enforced by British intelligence at Bletchley Park – what are the pros and cons of operating on a strictly need-to-know basis? It did cause a certain reduplication of efforts and possibly lowered morale, if it had not been for breaches of regulation mentioned by a handful of the coauthors. Feynman reports anecdotally regarding his participation in the Manhattan project that the lower-level scientists and engineers were motivated to work harder and perhaps more savvily once they had been clued in to what the overall project was about and what its technical goals were. Copeland offers nothing about how the decrypted intercepts could be used to gain an advantage in the conduct of the war without giving away to the German commanders the fact that their code had been compromised – in any event, decisions of this nature lay outside the purview of the codebreakers at Bletchley Park. The reader will also want to reflect on the crucial role played by oversights both on the part of German high commanders and on the part of lowly radio operators: though their security procedures were steadily tightened during the course of the war, these very human shortcomings proved ultimately decisive in losing the war for the Nazis. Another interesting point: Copeland declines to speculate on why Churchill ordered the Colossus machines and records of decoded intercepts destroyed after the cessation of hostilities in the European theater. Just a conjecture, but he may have wished to erase from the historical record his role in underwriting the Allies’ inaction with respect to the Holocaust (the Allied leaders felt that their strategic air forces were too tied up by the all-out effort to commit war crimes against German civilians for them to have any spare capacity to dedicate to a fight to stop the Nazis from committing war crimes of their own against Jews). Most of all, Copeland’s solid history of the Colossus conveys a feeling for what it is like to wage war: one has to exploit literally every opportunity or loophole at one’s disposal in the fight to wrest a marginal advantage over the opponent – this reviewer finds it fascinating how the British cryptanalysts could, for instance, rely on apparently contingent features of the very letter assignments in the binary table used by Tunny to streamline their algorithms just enough to derive a little extra edge. To be canny and wily counts for more than any number of armored divisions!

  3. 4 out of 5

    Jakub Šimek

    The book introduces some previously unknown (to the public anyway) information and dispels many common myths about code breaking in WW2 and about the birth of modern computing. I appreciate the technical detail of the book, which lets you follow the logic that the code breakers used in order to 'beat' the ciphers and ciphering machines. Included is also a rather detailed explanation of the machines involved, with obvious emphasis on the German Tunny machine and the computers constructed to break The book introduces some previously unknown (to the public anyway) information and dispels many common myths about code breaking in WW2 and about the birth of modern computing. I appreciate the technical detail of the book, which lets you follow the logic that the code breakers used in order to 'beat' the ciphers and ciphering machines. Included is also a rather detailed explanation of the machines involved, with obvious emphasis on the German Tunny machine and the computers constructed to break it, but some other machines are also mentioned, with their workings briefly explained. What I didn't like that much is that the book is a collection of more or less disconnected essays by over a dozen of authors. This results in some things being explained multiple times by multiple people in multiple ways. This is not only rather tedious at times, but I've also found some of the re-explanations (and jumps all over the timeline) confusing. While this format might be more valuable to a historian, I would prefer if professor Copeland instead took all the information he got from the sources and compiled into a single cohesive narrative.

  4. 4 out of 5

    Bill Leach

    This book describes the work carried out at Bletchley Park during World War II to break German military messages. It is a series of 26 chapters and 12 appendices, written by those with a detailed knowledge of the work at Bletchley Park. Many of the authors were directly involved, including Thomas Flowers, Donald Michie, Max Newman and William Tutte. The material is quite technical, describing the code breaking processes in detail. As the Colossus machines were destroyed at the end of the war and This book describes the work carried out at Bletchley Park during World War II to break German military messages. It is a series of 26 chapters and 12 appendices, written by those with a detailed knowledge of the work at Bletchley Park. Many of the authors were directly involved, including Thomas Flowers, Donald Michie, Max Newman and William Tutte. The material is quite technical, describing the code breaking processes in detail. As the Colossus machines were destroyed at the end of the war and all material classified, this book is provides detail that had previously been unavailable. Soon after the First World War ended, the German inventor Arthur Scherbius patented the Enigma cipher machine. It was based on a set of wheels with fixed wiring that translates each letter, the wheels advancing after each letter in the nature of a mechanical counter. The initial setting specifies the choice of wheels from a larger set and their starting positions. During the second World War, the German military used machines based upon the Enigma concept. The British used the "fish" family of names to refer to the German ciphers and the machines that generated them. - Tunny was used by the army and over land links, with the Lorenz SZ40 machine - Sturgeon was used by the navy and air force, with the more complex T-52 (four models a/b through e) - Thrasher was used only at the end of the war, with the Siemens T43 one-time code machine, Decryption of Tunny was primarily done with a machine designed by Alan Turing called the bombe. The first attempt to decrypt the Sturgeon cipher was done with an electro-mechanical machine called the Heath Robinson. Colossus - the world's first programmable digital electronic computer - followed, based on ideas from Max Newman, William Tutte and Alan Turing. Tommy Flowers was the chief designer. The book provides insight into the logistics of the code breaking - the methods used, the step-wise process, the compartmental methods to maximize security. Of interest is the development of techniques over time that improved the code breaking, but also the setbacks as the Germans updated their machines and procedures. Classified until recently, the roles of various individuals are described - it is clear that the brilliant engineer Thomas Flowers was the chief designer of Colossus. Descriptions of the personalities are interesting, giving insight into what were Alan Turing, Hugh Alexander, Max Newman and others really like. The book is important as much speculative and fictional work (for example the film, The Imitation Game) has incorrectly portrayed the Bletchley Park operations.

  5. 5 out of 5

    Peter

    A phenomenal collection of historical reminiscences of British codebreaking and the development of the first electronic computers during World War 2. It may not be perfect but then it was written 60 years after the event. That it exists at all is a huge bonus. I enjoyed the cryptography too. Just enough detail to understand the principles involved. Not logically laid out and a lot of repetition, but that’s the nature of the book.

  6. 4 out of 5

    Jules Bertaut

    This book is about Colossus, the electronic computer used to break one of the German ciphers in WWII. It's probably a bit niche interest because it gets rather into the technical details of the cipher, how decrypting it worked, and the computer. I thought it was really interesting, though! This book is about Colossus, the electronic computer used to break one of the German ciphers in WWII. It's probably a bit niche interest because it gets rather into the technical details of the cipher, how decrypting it worked, and the computer. I thought it was really interesting, though!

  7. 5 out of 5

    Al

    Although a struggle to get through in places, overall, Colossus is a spell-binding chronicle of Bletchley Park, Britain's top secret agency charged with breaking of German military codes during World War II. The story is told from many viewpoints and many of chapters are written by the original masterminds of the operation. Due to the many authors, the story is a bit uneven and repetition abounds. But the latter is not all bad, since the subject matter can be confusing to the non-cryptologically Although a struggle to get through in places, overall, Colossus is a spell-binding chronicle of Bletchley Park, Britain's top secret agency charged with breaking of German military codes during World War II. The story is told from many viewpoints and many of chapters are written by the original masterminds of the operation. Due to the many authors, the story is a bit uneven and repetition abounds. But the latter is not all bad, since the subject matter can be confusing to the non-cryptologically inclined reader. Although you really don't have to comprehend the math behind the story to enjoy the book, a basic understanding adds greatly to realizing the daunting task these pioneers faced -- and their resounding success! In my opinion, it is worthwhile to take the time to at least work through the rudimentary examples of cryptography and cryptanalysis provided. In addition, some of the denser chapters may require a second reading to get the point. One of the book's strong points is the illumination of the roles that many obscure figures, e.g., Thomas Flowers and Max Newman, play in the embryogenesis of digital computing. Due to British intelligence repression, they usually get little or no credit in most histories of computing. The towering Alan Turing's role in Bletchley is somewhat minimized, but I think this is primarily done to emphasize the roles of his less well known co-workers. In short, Colossus will fascinate those readers interested the history of computing and WWII espionage alike.

  8. 4 out of 5

    Ian

    At times the technicality of the mathematics beat me, but that's because I'm too lazy to put in the effort so no criticism of book or authors and please don't let that comment put anyone off! Note that I said authors, as although Copeland is clearly the main author and editor there are about 15 contributors (including Roy Jenkins who worked as a code breaker at Bletchley Park before his career in politics). The book is a collection of stories by individuals who worked on breaking the "Tunny" ciph At times the technicality of the mathematics beat me, but that's because I'm too lazy to put in the effort so no criticism of book or authors and please don't let that comment put anyone off! Note that I said authors, as although Copeland is clearly the main author and editor there are about 15 contributors (including Roy Jenkins who worked as a code breaker at Bletchley Park before his career in politics). The book is a collection of stories by individuals who worked on breaking the "Tunny" cipher, at first by hand but later with the assistance of Colossus, arguably the world's first electronic computer - certainly predating ENIAC always claimed by the Americans to be the first. Immediately after the war Churchill ordered all the Colossi machines to be destroyed and the work on tunny remained secret until 1970 - some elements are still classified apparently. This has resulted in some stories of great pathos, wives who could never tell their husbands what they did in the war, and one of the authors describes his great sadness that both his PPP parents died without ever knowing that their son had made such a significant contribution to the fight against Hitler. Eisenhower stated that the work done by the Colossus teams had shortened the war by at least two years! So, not the easiest of reads but very rewarding and most enjoyable.

  9. 5 out of 5

    Tony

    Very informative. Contained a lot of information which was recently declassified, at the time of publishing. A common misconception is that Colossus was created to break Enigma. That is incorrect. Previous machines had already accomplished that. Colossus was created to break the German Lorenz cipher, which wasn't nearly so portable as Enigma but was heavily used for orders to field units for the Wehrmakt and the Luftwaffe. Lorenz was a teleprinter, which took messages in punched tape, encrypted t Very informative. Contained a lot of information which was recently declassified, at the time of publishing. A common misconception is that Colossus was created to break Enigma. That is incorrect. Previous machines had already accomplished that. Colossus was created to break the German Lorenz cipher, which wasn't nearly so portable as Enigma but was heavily used for orders to field units for the Wehrmakt and the Luftwaffe. Lorenz was a teleprinter, which took messages in punched tape, encrypted them and transmitted them. Enigma was, due to the difficulty of its use, used for relatively messages. Lorenz could, and routinely did, transmit pages of text at a time. The brilliance of the people working at Bletchley Park is hard to fathom. The people who created Colossus and broke the Lorenz cipher never had access to one until after the war. From the encrypted messages alone, they determined the basic workings of the machine and how to break it. It is a rather long and ponderous tome. If you really enjoy a deep dive into technological history, this book delivers.

  10. 4 out of 5

    David

    For those who are fascinated by code-breaking this is a must read. The mathematics is beyond me, but there's more here. The characters who worked at Bletchley Park, the secrecy within the place. The worlds first real computer was Colossus. At wars end, everything was ordered destroyed. Britain could have been at the front of computer technology. Paranoia about military secrets set the country on a course from which it never recovered. Britain won the war, and lost it's empire. Churchill and othe For those who are fascinated by code-breaking this is a must read. The mathematics is beyond me, but there's more here. The characters who worked at Bletchley Park, the secrecy within the place. The worlds first real computer was Colossus. At wars end, everything was ordered destroyed. Britain could have been at the front of computer technology. Paranoia about military secrets set the country on a course from which it never recovered. Britain won the war, and lost it's empire. Churchill and others had no idea of the potential of computers.

  11. 5 out of 5

    Doug Haskin

    Contains some interesting personal histories of code breaking and primitive computing at Bletchley Park, but much of the book is quite technical in nature and difficult to follow if you're not strong in mathematics. Contains some interesting personal histories of code breaking and primitive computing at Bletchley Park, but much of the book is quite technical in nature and difficult to follow if you're not strong in mathematics.

  12. 5 out of 5

    Lizzie

    Excellent thorough exploration if the ongoing at bletchley Park. The collection of essays introduces you to the concepts of the colossus in a way that any reader could understand and offers multiple perspectives on the people who worked there.

  13. 4 out of 5

    Gabriel

    A somewhat dry but otherwise well-written history, written by the Colossus' constructors themselves. Essential to anyone with an interest in the history of computing. A somewhat dry but otherwise well-written history, written by the Colossus' constructors themselves. Essential to anyone with an interest in the history of computing.

  14. 4 out of 5

    Alain van Hoof

    A good balance between personal stories en technical details. After reading other books about Bletchley Park it looked like all was done there was decrypting Enigma, this books shows otherwise.

  15. 4 out of 5

    Tim

    We know about the Enigma machine but this is about Tunny, a more advanced machine used in the later parts of the war that the British also broke into. Based on material only declassified in 2000.

  16. 5 out of 5

    Aron Edwards

  17. 4 out of 5

    Deb

  18. 5 out of 5

    Christine Burns

  19. 4 out of 5

    Lisa Stimmell

  20. 5 out of 5

    Barry Hill

  21. 5 out of 5

    Mark

  22. 4 out of 5

    JOHN G

  23. 4 out of 5

    Andy

  24. 5 out of 5

    Tom

  25. 5 out of 5

    Cleveland Thornton

  26. 4 out of 5

    Jim Masson

  27. 5 out of 5

    Paul Goggin

  28. 4 out of 5

    Len

  29. 4 out of 5

    Ken

  30. 5 out of 5

    Neil Paul

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