The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography by Simon Singh (PDF)

Description

In his first book since the bestselling Fermat’s Enigma, Simon Singh offers the first sweeping history of encryption, tracing its evolution and revealing the dramatic effects codes have had on wars, nations, and individual lives. From Mary, Queen of Scots, trapped by her own code, to the Navajo Code Talkers who helped the Allies win World War II, to the incredible (and incredibly simple) logisitical breakthrough that made Internet commerce secure, The Code Book tells the story of the most powerful intellectual weapon ever known: secrecy.Throughout the text are clear technical and mathematical explanations, and portraits of the remarkable personalities who wrote and broke the world’s most difficult codes. Accessible, compelling, and remarkably far-reaching, this book will forever alter your view of history and what drives it. It will also make you wonder how private that e-mail you just sent really is.

User’s Reviews

Editorial Reviews: Amazon.com Review People love secrets. Ever since the first word was written, humans have sent coded messages to each other. In The Code Book, Simon Singh, author of the bestselling Fermat’s Enigma, offers a peek into the world of cryptography and codes, from ancient texts through computer encryption. Singh’s compelling history is woven through with stories of how codes and ciphers have played a vital role in warfare, politics, and royal intrigue. The major theme of The Code Book is what Singh calls “the ongoing evolutionary battle between codemakers and codebreakers,” never more clear than in the chapters devoted to World War II. Cryptography came of age during that conflict, as secret communications became critical to both sides’ success.Confronted with the prospect of defeat, the Allied cryptanalysts had worked night and day to penetrate German ciphers. It would appear that fear was the main driving force, and that adversity is one of the foundations of successful codebreaking. In the information age, the fear that drives cryptographic improvements is both capitalistic and libertarian–corporations need encryption to ensure that their secrets don’t fall into the hands of competitors and regulators, and ordinary people need encryption to keep their everyday communications private in a free society. Similarly, the battles for greater decryption power come from said competitors and governments wary of insurrection.The Code Book is an excellent primer for those wishing to understand how the human need for privacy has manifested itself through cryptography. Singh’s accessible style and clear explanations of complex algorithms cut through the arcane mathematical details without oversimplifying. –Therese Littleton Review “It would be hard to imagine a clearer or more fascinating presentation. . . . Mr. Singh gives cryptography not only its historical dimension but its human one.” –The New York Times”Entertaining and satisfying. . . . Offers a fascinating glimpse into the mostly secret competition between codemakers and codebreakers.” –USA Today “A good read that, bless it, makes the reader feel a bit smarter when it’s done. Singh’s an elegant writer and well-suited to the task of leading the mathematically perplexed through areas designed to be tricky.” –Seattle Weekly “An absorbing tale of codemaking and codebreaking over the centuries.” –Scientific American”Singh spins tales of cryptic intrigue in every chapter.” –The Wall Street Journal”Brings together…the geniuses who have secured communications, saved lives, and influenced the fate of nations. A pleasure to read.” –Chicago Tribune”Enthralling…commendably lucid…[Singh’s] book provides a timely and entertaining summary of the subject.” –The Economist From the Inside Flap book since the bestselling Fermat’s Enigma, Simon Singh offers the first sweeping history of encryption, tracing its evolution and revealing the dramatic effects codes have had on wars, nations, and individual lives. From Mary, Queen of Scots, trapped by her own code, to the Navajo Code Talkers who helped the Allies win World War II, to the incredible (and incredibly simple) logisitical breakthrough that made Internet commerce secure, The Code Book tells the story of the most powerful intellectual weapon ever known: secrecy.Throughout the text are clear technical and mathematical explanations, and portraits of the remarkable personalities who wrote and broke the world’s most difficult codes. Accessible, compelling, and remarkably far-reaching, this book will forever alter your view of history and what drives it. It will also make yo wonder how private that e-mail you just sent really is. From the Back Cover In his first book since the bestselling Fermat’s Enigma, Simon Singh offers the first sweeping history of encryption, tracing its evolution and revealing the dramatic effects codes have had on wars, nations, and individual lives. From Mary, Queen of Scots, trapped by her own code, to the Navajo Code Talkers who helped the Allies win World War II, to the incredible (and incredibly simple) logisitical breakthrough that made Internet commerce secure, The Code Book tells the story of the most powerful intellectual weapon ever known: secrecy. Throughout the text are clear technical and mathematical explanations, and portraits of the remarkable personalities who wrote and broke the world’s most difficult codes. Accessible, compelling, and remarkably far-reaching, this book will forever alter your view of history and what drives it. It will also make yo wonder how private that e-mail you just sent really is. About the Author Simon Singh received his Ph.D. in physics from Cambridge University. A former BBC producer, he directed and co-produced an award-winning documentary film on Fermat’s Last Theorem that aired on PBS’s Nova series and formed the basis of his bestselling book, Fermat’s Enigma. He lives in London. Excerpt. © Reprinted by permission. All rights reserved. On the morning of Wednesday, 15 October 1586, Queen Mary entered the crowded courtroom at Fotheringhay Castle. Years of imprisonment and the onset of rheumatism had taken their toll, yet she remained dignified, composed and indisputably regal. Assisted by her physician, she made her way past the judges, officials and spectators, and approached the throne that stood halfway along the long, narrow chamber. Mary had assumed that the throne was a gesture of respect towards her, but she was mistaken. The throne symbolised the absent Queen Elizabeth, Mary’s enemy and prosecutor. Mary was gently guided away from the throne and towards the opposite side of the room, to the defendant’s seat, a crimson velvet chair.Mary Queen of Scots was on trial for treason. She had been accused of plotting to assassinate Queen Elizabeth in order to take the English crown for herself. Sir Francis Walsingham, Elizabeth’s Principal Secretary, had already arrested the other conspirators, extracted confessions, and executed them. Now he planned to prove that Mary was at the heart of the plot, and was therefore equally culpable and equally deserving of death.Walsingham knew that before he could have Mary executed, he would have to convince Queen Elizabeth of her guilt. Although Elizabeth despised Mary, she had several reasons for being reluctant to see her put to death. First, Mary was a Scottish queen, and many questioned whether an English court had the authority to execute a foreign head of state. Second, executing Mary might establish an awkward precedent — if the state is allowed to kill one queen, then perhaps rebels might have fewer reservations about killing another, namely Elizabeth. Third, Elizabeth and Mary were cousins, and their blood tie made Elizabeth all the more squeamish about ordering her execution. In short, Elizabeth would sanction Mary’s execution only if Walsingham could prove beyond any hint of doubt that she had been part of the assassination plot.The conspirators were a group of young English Catholic noblemen intent on removing Elizabeth, a Protestant, and replacing her with Mary, a fellow Catholic. It was apparent to the court that Mary was a figurehead for the conspirators, but it was not clear that she had actually given her blessing to the conspiracy. In fact, Mary had authorised the plot. The challenge for Walsingham was to demonstrate a palpable link between Mary and the plotters.On the morning of her trial, Mary sat alone in the dock, dressed in sorrowful black velvet. In cases of treason, the accused was forbidden counsel and was not permitted to call witnesses. Mary was not even allowed secretaries to help her prepare her case. However, her plight was not hopeless because she had been careful to ensure that all her correspondence with the conspirators had been written in cipher. The cipher turned her words into a meaningless series of symbols, and Mary believed that even if Walsingham had captured the letters, then he could have no idea of the meaning of the words within them. If their contents were a mystery, then the letters could not be used as evidence against her. However, this all depended on the assumption that her cipher had not been broken.Unfortunately for Mary, Walsingham was not merely Principal Secretary, he was also England’s spymaster. He had intercepted Mary’s letters to the plotters, and he knew exactly who might be capable of deciphering them. Thomas Phelippes was the nation’s foremost expert on breaking codes, and for years he had been deciphering the messages of those who plotted against Queen Elizabeth, thereby providing the evidence needed to condemn them. If he could decipher the incriminating letters between Mary and the conspirators, then her death would be inevitable. On the other hand, if Mary’s cipher was strong enough to conceal her secrets, then there was a chance that she might survive. Not for the first time, a life hung on the strength of a cipher.The Evolution of Secret WritingSome of the earliest accounts of secret writing date back to Herodotus, ‘the father of history’ according to the Roman philosopher and statesman Cicero. In The Histories, Herodotus chronicled the conflicts between Greece and Persia in the fifth century bc, which he viewed as a confrontation between freedom and slavery, between the independent Greek states and the oppressive Persians. According to Herodotus, it was the art of secret writing that saved Greece from being conquered by Xerxes, King of Kings, the despotic leader of the Persians.The long-running feud between Greece and Persia reached a crisis soon after Xerxes began constructing a city at Persepolis, the new capital for his kingdom. Tributes and gifts arrived from all over the empire and neighbouring states, with the notable exceptions of Athens and Sparta. Determined to avenge this insolence, Xerxes began mobilising a force, declaring that ‘we shall extend the empire of Persia such that its boundaries will be God’s own sky, so the sun will not look down upon any land beyond the boundaries of what is our own’. He spent the next five years secretly assembling the greatest fighting force in history, and then, in 480 bc, he was ready to launch a surprise attack.However, the Persian military build-up had been witnessed by Demaratus, a Greek who had been expelled from his homeland and who lived in the Persian city of Susa. Despite being exiled he still felt some loyalty to Greece, so he decided to send a message to warn the Spartans of Xerxes’ invasion plan. The challenge was how to dispatch the message without it being intercepted by the Persian guards. Herodotus wrote:As the danger of discovery was great, there was only one way in which he could contrive to get the message through: this was by scraping the wax off a pair of wooden folding tablets, writing on the wood underneath what Xerxes intended to do, and then covering the message over with wax again. In this way the tablets, being apparently blank, would cause no trouble with the guards along the road. When the message reached its destination, no one was able to guess the secret, until, as I understand, Cleomenes’ daughter Gorgo, who was the wife of Leonides, divined and told the others that if they scraped the wax off, they would find something written on the wood underneath. This was done; the message was revealed and read, and afterwards passed on to the other Greeks.As a result of this warning, the hitherto defenceless Greeks began to arm themselves. Profits from the state-owned silver mines, which were usually shared among the citizens, were instead diverted to the navy for the construction of two hundred warships.Xerxes had lost the vital element of surprise and, on 23 September 480 bc, when the Persian fleet approached the Bay of Salamis near Athens, the Greeks were prepared. Although Xerxes believed he had trapped the Greek navy, the Greeks were deliberately enticing the Persian ships to enter the bay. The Greeks knew that their ships, smaller and fewer in number, would have been destroyed in the open sea, but they realised that within the confines of the bay they might outmanoeuvre the Persians. As the wind changed direction the Persians found themselves being blown into the bay, forced into an engagement on Greek terms. The Persian princess Artemisia became surrounded on three sides and attempted to head back out to sea, only to ram one of her own ships. Panic ensued, more Persian ships collided and the Greeks launched a full-blooded onslaught. Within a day, the formidable forces of Persia had been humbled.Demaratus’ strategy for secret communication relied on simply hiding the message. Herodotus also recounted another incident in which concealment was sufficient to secure the safe passage of a message. He chronicled the story of Histaiaeus, who wanted to encourage Aristagoras of Miletus to revolt against the Persian king. To convey his instructions securely, Histaiaeus shaved the head of his messenger, wrote the message on his scalp, and then waited for the hair to regrow. This was clearly a period of history that tolerated a certain lack of urgency. The messenger, apparently carrying nothing contentious, could travel without being harassed. Upon arriving at his destination he then shaved his head and pointed it at the intended recipient.Secret communication achieved by hiding the existence of a message is known as steganography, derived from the Greek words steganos, meaning ‘covered’, and graphein, meaning ‘to write’. In the two thousand years since Herodotus, various forms of steganography have been used throughout the world. For example, the ancient Chinese wrote messages on fine silk, which was then scrunched into a tiny ball and covered in wax. The messenger would then swallow the ball of wax. In the fifteenth century, the Italian scientist Giovanni Porta described how to conceal a message within a hard-boiled egg by making an ink from a mixture of one ounce of alum and a pint of vinegar, and then using it to write on the shell. The solution penetrates the porous shell, and leaves a message on the surface of the hardened egg albumen, which can be read only when the shell is removed. Steganography also includes the practice of writing in invisible ink. As far back as the first century ad, Pliny the Elder explained how the ‘milk’ of the thithymallus plant could be used as an invisible ink. Although transparent after drying, gentle heating chars the ink and turns it brown. Many organic fluids behave in a similar way, because they are rich in carbon and therefore char easily. Indeed, it is not unknown for modern spies who have run out of standard-issue invisible ink to improvise by using their own urine. The longevity of steganography illustrates that it certainly offers a modicum of security, but it suffers from a fundamental weakness. If the messenger is searched and the message is discovered, then the contents of the secret communication are revealed at once. Interception of the message immediately compromises all security. A thorough guard might routinely search any person crossing a border, scraping any wax tablets, heating blank sheets of paper, shelling boiled eggs, shaving people’s heads, and so on, and inevitably there will be occasions when the message is uncovered. Hence, in parallel with the development of steganography, there was the evolution of cryptography, derived from the Greek word kryptos, meaning ‘hidden’. The aim of cryptography is not to hide the existence of a message, but rather to hide its meaning, a process known as encryption. To render a message unintelligible, it is scrambled according to a particular protocol which is agreed beforehand between the sender and the intended recipient. Thus the recipient can reverse the scrambling protocol and make the message comprehensible. The advantage of cryptography is that if the enemy intercepts an encrypted message, then the message is unreadable. Without knowing the scrambling protocol, the enemy should find it difficult, if not impossible, to recreate the original message from the encrypted text.Although cryptography and steganography are independent, it is possible to both scramble and hide a message to maximise security. For example, the microdot is a form of steganography that became popular during the Second World War. German agents in Latin America would photographically shrink a page of text down to a dot less than 1 millimetre in diameter, and then hide this microdot on top of a full stop in an apparently innocuous letter. The first microdot to be spotted by the FBI was in 1941, following a tip-off that the Americans should look for a tiny gleam from the surface of a letter, indicative of smooth film. Thereafter, the Americans could read the contents of most intercepted microdots, except when the German agents had taken the extra precaution of scrambling their message before reducing it. In such cases of cryptography combined with steganography, the Americans were sometimes able to intercept and block communications, but they were prevented from gaining any new information about German spying activity. Of the two branches of secret communication, cryptography is the more powerful because of this ability to prevent information from falling into enemy hands.In turn, cryptography itself can be divided into two branches, known as transposition and substitution. In transposition, the letters of the message are simply rearranged, effectively generating an anagram. For very short messages, such as a single word, this method is relatively insecure because there are only a limited number of ways of rearranging a handful of letters. For example, three letters can be arranged in only six different ways, e.g. cow, cwo, ocw, owc, wco, woc. However, as the number of letters gradually increases, the number of possible arrangements rapidly explodes, making it impossible to get back to the original message unless the exact scrambling process is known. For example, consider this short sentence. It contains just 35 letters, and yet there are more than 50,000,000,000,000,000,000,000,000,000,000 distinct arrangements of them. If one person could check one arrangement per second, and if all the people in the world worked night and day, it would still take more than a thousand times the lifetime of the universe to check all the arrangements. Read more

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐I have been fascinated by cryptography since my age was single digits, and enjoyed decrypting messages and developing codes when I was a teenager. I was introduced to public key cryptography in 1977 by Martin Gardner’s Mathematical Games column in Scientific American, and was thrilled by it. (Yes, “thrilled”. Really. I was.) What’s more, I now have a degree in mathematics. In my Number Theory course the prof taught us the RSA algorithm.All that is to say, I didn’t expect to learn anything new about cryptography from The Code Book. I read it mainly in the hope of reading some good stories from the history of cryptography. Those expectations were fulfilled. I am thus in a position to tell you whether Simon Singh is a good story-teller (he is!), whether his presentation of the math and science of cryptography is accurate (it is!), and whether he explains it well (mostly yes).Although I may be projecting, my impression is that Singh wrote this book mainly for the same reason I read it, for the sake of the stories. I was particularly fascinated by the stories of the Babington Plot and how Elizabeth’s secretary Walsingham (a devious snake if ever there was one) used codebreaking and forgery to induce the plotters to hang themselves and their queen, of the story of the Zimmermann Telegram and how English codebreakers sneakily used it to induce President Wilson to set aside USA neutrality, of the decipherment of Linear B (not, as Singh forthrightly admits, strictly a story of cryptography, but certainly in the same intellectual ballpark), and the repeated discovery of public key cryptography, first, secretly, by researchers at GCHQ (the UK’s cryptography establishment), then later publicly by academic researchers at Stanford University and MIT. The story of the World War II breaking of German Enigma codes is also fascinating, but it has been told many times elsewhere. (Alan Turing: The Enigma is the best account I have read.) And if you ever suffered from the delusion that the English are straightforward and honest people, this book will cure you.I got the impression (again, this may just be me projecting) that Singh describes the technical details of the codes mainly for the sake of the stories. He wants you to understand how difficult the intellectual challenges were and thereby to appreciate the brilliance of the codemakers and especially the codebreakers. He does what mathematicians always do when it is necessary to describe sophisticated mathematical concepts to non-mathematicians — he disguises the math by describing it in non-math terms, as far as possible. I didn’t feel this was entirely successful. I suspect many readers will find his description of the technicalities of code-making and code-breaking heavy going.The least satisfactory chapters were the last two, “Pretty Good Privacy” and “A Quantum Leap into the Future”. “Pretty Good Privacy” discusses Philip Zimmermann’s development of PGP as an entré into the fraught societal questions raised by public key cryptography and a burgeoning Internet. It’s a valiant effort, but 1999 was long ago in Internet time, and consequently this chapter is badly dated. PGP itself has virtually disappeared from the landscape, displaced by such things as openssl. The final chapter on quantum computing and quantum cryptography, necessarily begins with an introduction to quantum mechanics. Singh, alas, does as bad a job as everyone else of explaining quantum mechanics. He begins with this tired quote from Niels Bohr,”Anyone who can contemplate quantum mechanics without getting dizzy hasn’t understood it.”Bohr wrote that about a hundred years ago. The state of the art has advanced since then. In the twenty-first century thousands of physics undergraduates learn quantum mechanics every year. Every one of them understands it better than Bohr did, not because they’re smarter than Bohr was — most of them are not even close — but because they have the benefit of a hundred years of better explanations than Bohr had access to. That’s how science works! Unfortunately, the state of popular explanation of quantum mechanics is dismal. Part of the reason that so few nonspecialists understand quantum mechanics is that nonspecialist explanations are almost uniformly dreadful. They all begin, as Singh does, “This is incomprehensible, and you are not going to understand it.” That is a doubleplusungood way to begin an explanation, of anything. I will, however, say this for Singh: although his explanation of quantum mechanics is best ignored, his description of the cryptographic implications is generally good.

⭐What I would like to remember:- I don’t think I had ever been drawn to study cryptography before reading this book, but for sure the book raised awareness and a new interest for me.- While we tend to associate cryptography and encoding with technology / computers etc, the reality is that this is a science that has existed for centuries, and has been very influential in matters of state and military actions for almost all of Western History- I was finally able to understand the concept of a public / private key scheme: essentially every “user” has a public and a private key: The public key is known by everyone but can only be used to encrypt information. The private key is only known by the owner and it is used to decrypt. The relationship between the Public and the private key is only known by the “owner” and is determined using extremely large prime numbers which are very hard to guess by brute force (this could be challenged by quantum computers)- The book was published in the late 1990’s (1999, I think), and since then so much has happened in terms of development of the internet and information sharing by non-government / non-military parties. I am very curious to know how things have evolved since then.- There is a concept called Quantum encryption, which according to the book would be really unbreakable (not just practically, but also in theory imposible).- I really want to learn more about this topic.

⭐Like all narrative non-fictional works that, eventually in this case, deal with technical subjects whose details are beyond the scope of the non-specialist reader, this book attempts to strike a balance between two extremes, between a book so chock-full of technical detail that it reads like a textbook and a book that skimps so completely on the heart of the matter at hand that it can only be described as fluff. Singh has done a remarkable job in balancing the two here, it seems to me, and the book is worth any reader’s time whose interest is piqued by cryptography.Singh is singularly aided by his subject matter here. This book was recommended to me by a fellow poster on a crossword puzzle blog which I frequent, as a daily solver of the New York Times crossword. The discussions on the blog vary from the whimsical to the technical with all manner of things mooted. So goes Singh’s book as well. But what makes this possible is that cryptography and cryptanalysis, for most of human history, has been no more complex, au fond, than a very difficult crossword puzzle. And one is not surprised to see a crossword used during WWII by the British to test potential candidates for work at top secret Bletchley Park, which was responsible for cracking Germany’s “Enigma” code. The crossword is provided in the book and was jolly fun to solve.It seems to me that up to the Vigenère polyalphabetic coding, known for centuries as “le chiffre indéchifferable”, anyone with an interest in this book could understand and create such a cipher and write an encrypted message in it. Indeed, it’s in deciphering such messages without the “keyword” that the technical going gets somewhat involved and perhaps beyond the ken of some readers not familiar with basic statistical analysis, and, not coincidentally, this decipherment of such encryptions is where maths starts to predominate. But it’s certainly not difficult to understand the concept of how these encryptions are deciphered, it’s merely very tedious and painstaking to do it as Charles Babbage finally did in the 19th Century.Up to this point, for this reader in any event, no trade-off was necessary and Singh is free to fill his tale of codes and ciphers with histories which hinge upon them, starting with the life and death of Mary, Queen of Scots. Also, he makes an elegant segue in the tale of how the Linear B tablets were finally translated, and the toing and froing of certain egotistical archaeologists etc. – It should be noted here the final decipherment and translation of Linear B was the cumulative work of men (and one woman) of genius who were linguistic prodigies. – Again, pass the 19th century and the non-specialist becomes more than a tad lost in the, literally and figuratively, nuts and bolts of Enigma machines and multi-lingual scholarship and fluency.Thus, it’s no surprise that the ending of the book was the weakest part for me. Though it must be said that Singh goes out of his way to use “Alice, Bob, Eve” analogies to make the concepts clearer most effectively, being able to do what the main players in the tale are doing is far beyond the amateur’s grasp. Also, the book is thirteen years old and the final sections dealing with computer encryption seem a bit dated already.In sum though, a very pleasing, well-written book about the perennial human need to keep matters secret.

⭐Simon Singh provides the reader with an overview of the history of cryptology and brings to the reader’s attention events in history that would probably have had different outcomes had it not been for the achievements of some historical figures – mostly unknown to us today – like Thomas Phelippes who deciphered and forged an encrypted message to Mary, Queen of Scots, thereby forcing her to effectively sign her own death warrant, and Marian Rejewski who provided the groundwork on deciphering the Enigma machine before handing his research over to the British; his enthusiasm for the subject shines through at every page. He also aims to set the record straight for a few unsung heroes, mainly from recent history who, due to the secrecy act, were forbidden from publicly claiming credit for their work in cryptology at the time. Most notably amongst them is Alan Turing who helped crack the Enigma cipher, but also Tommy Flowers who single-handedly built Colossus, the precursor to the modern digital computer but who had to destroy the blueprints after the war, as well as Clifford Cocks and Malcolm Williamson who invented the asymmetric cipher and public-key cryptography four years before the Americans but were sworn to secrecy. I also enjoyed his brief foray into the decipherment of ancient texts like the Egyptian hieroglyphics and the Minoan script of Linear B, but Simon Singh’s main achievement lies in his ability to bring across such tricky issues like key distribution, public-key cryptography and quantum cryptography in a simple and lucid manner to a mainly non-technically minded person like me. My only criticism and one that has got nothing to do with the author, is the fact that this book was written more than ten years ago when e-commerce was still in its infancy; since then the world has seen a massive leap in terms of financial transactions being conducted over the internet and even seen the arrival of internet banking and with it the need for ever better security for the individual and companies trading over the internet. I would be most interested to read a topical update in which he covers the last ten years and the impact this has had on cryptography.

⭐I was reading about cryptography somewhere and it recommended this book, which I subsequently purchased. Absolutely unputdownable! Cryptography and codes have been around for thousands of years, and you can follow the progression from the simplest, to a brief introduction of the totally unbreakable quantum encryption. Mary Queen of Scots plotted to kill Queen Elizabeth by sending coded messages to her accomplices. However, the Queen’s code breakers could decipher everything she wrote and condemned Mary to death. Just one of the Amazon facts you will read in this book.

⭐Almost perfect for a layman’s introductory book on cryptography/ cryptanalysis. 5 stars for all the historical introduction from Ceasar Shift, substitution/transposition, frequency analysis and linguistics, monoalphabets, polyalphabets, Vigenere and Babbage, Turing and the naval Enigma, but minus 0.5-1 stars because modern encryption/decryption techniques were a little rushed relative to the earlier historical half of the book and some applications were hardly mentioned. Interesting that Linear A and Etruscan had not been deciphered at the time this book was written.Although I bought this book late, and technology has advanced since it was written, I was hoping to better understand encryption in the fields of computer science and technology (authentication and certificates on the internet, hashing of passwords, credit card technology…). There was a good intro on RSA and PGP, and I enjoyed the ending on photon traps and quantum computing. I wish there had been a little more on number theory (primes), a comparison of the many modern standards, the use of analysis in digital forensics, …something a little more technical but maybe there are other books for that.There are some dubious claims in the book that GCHQ invented asymetric public-key encryption ‘before’ Diffie-Hellman-Merkle and Rivest-Shamir-Aldeman. The claim being made is that GCHQ invented it shortly before (whatever they say, right?), but could not disclose their invention for reasons of national security. I realise that this story was put out in 1997 by GCHQ and not Simon Singh, but where is the evidence?What is more likely is that there were reasons of national security for not disclosing that, despite the huge budgets, the shadowy cold-war era monoliths GCHQ (and NSA) were totally outwitted by a handful of freedom loving academics like Whitfield Diffie, who saw this technology as a means of protecting free speech and, therefore, democracy.Kudos to Simon Singh for stating his suppor for the use of Zimmermann’s PGP in the book.The book concludes with a multiple stages code cracking challenge, which starts very easy and gets harder (there was a cash prize at the time).

⭐Having previously worked with encryption systems, I first read this book many years ago in order to get a better understanding of the underpinning principles of cryptography. As others have already conveyed, Simom Singh produced a very approachable book which neatly balanced the tasks of providing enough technical explanation of a very complex subject while avoiding the trap of overwhelming more ‘casual’ readers. Highly recommended!

⭐Great book if you have any interest in encryption. Covers from the early days of hiding messages by writing them on someones bald head before allowing the hair to grow all the way to the engima machine in world war 2. Book isnt too heavy for those who are not mathamaticians but explains modern encryption topics in an easily accessable way. Highly recommend it.

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