Κώδικες και μυστικά

by Simon Singh, Νάσος Κυριαζόπουλος (Translator)

Βασιλείς, στρατηγοί και κυβερνήτες κάθε εποχής «εναποθέτουν» στην «κρυπτογραφημένη» επικοινωνία την ασφαλή διακυβέρνηση χωρών και την αποτελεσματική διοίκηση στρατών. Όλοι τους έχουν απόλυτη συνείδηση του τι σημαίνει να πέσουν τα μηνύματα σε λάθος χέρια...

Το Κώδικες και Μυστικά πραγματεύεται την αέναη μονομαχία ανάμεσα σε εκείνους που επινοούν τους κώδικες και εκείνους που τους σπάζουν. Πρόκειται για έναν πόλεμο που χρησιμοποιεί όπλα από πολλές επιστήμες και κινητοποιεί μέσα που απαιτούν τις τελευταίες εξελίξεις της τεχνολογίας. Από τα μαθηματικά ως τη γλωσσολογία και από τη θεωρία της πληροφορικής ως τη κβαντική φυσική, αναζητούνται τρόποι διάρρηξης ή διασφάλισης του απορρήτου.
Καθώς η πληροφορία έχει εξελιχθεί σε πολυτιμότατο αγαθό και η επανάσταση στις επικοινωνίες έχει τη δυνατότητα να αλλάζει κοινωνίες, είναι φανερό ότι το παιχνίδι ανάμεσα σε «κωδικο-πλάστες» και «κωδικο-θραύστες» είναι αγώνας μέχρι τελικής πτώσεως.
Η ιστορική εξέλιξη των κωδίκων και οι κοινωνικές επιπτώσεις της θέτει σήμερα ερωτήματα πιο επίκαιρα από ποτέ: οι κοινωνίες θα επιλέξουν την προστασία του ιδιωτικού απορρήτου ή έναν αποτελεσματικότερο αστυνομικό έλεγχο; Ή μήπως υπάρχει συμβιβαστική λύση;

Το βιβλίο αυτό επιχειρεί να προβλέψει την έκβαση ενός ανοιχτού παιχνιδιού με απρόβλεπτες συνέπειες και τέλος...

Genres: Nonfiction, Science, History, Mathematics, Computer Science, Technology, Popular Science

608 pages, Paperback

Published May 1, 2001

About the author

Simon Lehna Singh, MBE is a British author who has specialised in writing about mathematical and scientific topics in an accessible manner. He is the maiden winner of the Lilavati Award.

His written works include Fermat's Last Theorem (in the United States titled Fermat's Enigma: The Epic Quest to Solve the World's Greatest Mathematical Problem), The Code Book (about cryptography and its history), Big Bang (about the Big Bang theory and the origins of the universe) and Trick or Treatment? Alternative Medicine on Trial (about complementary and alternative medicine).

He has also produced documentaries and works for television to accompany his books, is a trustee of NESTA, the National Museum of Science and Industry and co-founded the Undergraduate Ambassadors Scheme.

Reviews

[Paul · Rating 5 out of 5]

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And for those who care, here is the key to decode the above review:


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5 f p z
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Be warned, though; the key alone will not give you a complete decoding! :-)

And for those who can't be bothered, here's the decoded review:

This excellent book provides a fascinating history of codes and codebreaking from ancient Egypt to the modern day. In fact, it goes one step further than present day, and gives us a look at what the future may hold in this field.

The author writes about what could have been quite a dry subject with such enthusiasm and in such an engaging way that one can’t help but be drawn in. Before reading this book, I only had a very rudimentary knowledge of cryptography and am very much the layman. Singh explains things so well that you don’t need any prior knowledge of the subject to tackle this book; if I can understand it, anybody can! I’ll definitely be reading more of his work in the future.

Some of the topics covered here aren’t technically concerned with codes and codebreaking, but deal with the translation of ancient texts such as hieroglyphics. Ancient dead languages aren’t codes, as such, because they weren’t created with the intention of concealing the contents; quite the opposite, in fact; but they are relevant in that some of the techniques are shared with codebreaking. These chapters actually make for really interesting reading, so it’s a welcome diversion and one that Singh weaves into the rest of the book seamlessly.

Be warned, though; reading this book will make you want to delve deeper into the subject matter. Fortunately, the author provides a further reading list at the end of the book, so there are plenty of future delights in store!

P.S. If you actually went to the effort of decoding this review, you get a gold star. An imaginary gold star, but still…

[Mario the lone bookwolf · Rating 5 out of 5]

A journey through the history of coding, cryptography, and codebreaking.

From primitive to high tech
Chronologically arranged, the book begins in ancient times and describes simple forms of encryption such as shaving the head, tattooing a message, waiting a few weeks, or wrapping a leather strip with important information around a stick of specified thickness. The further the time progresses, the more complex the techniques become and get ever shorter expiration dates because of the specialists trying to crack them.

Very specific
The methods used are described in detail, which is sometimes too advanced for beginners, and because of this, it´s sometimes advisable to skim the purely theoretical descriptions as in my case (laziness and layman). The military historical and political aspects are anyway much more interesting for the philistines of applied science.

Alternative realities
Thus, in the race between decoders and creative code writers, not only the reputation of the technicians but often also the history of the world as we know it was at stake. An earlier, later, or even non-occurrence of an encryption or decryption technique would almost certainly have led to another current geopolitical map, unleashing close to any possible uchronic alternative timeline.

That escalated quickly
The closer the book comes to the present, the more explosive the stories become. Like for instance the possibility of an undecipherable encryption technique, which should, as wanted by the military, never be widely used because of its complexity and importance for cyberwarfare superiority.

The big unanswered question at the end of the book is whether today's very secure encryption technology has already been silently banished into the area of no longer total reliability. The suddenly antiquated encryption technique could be owned by a nemesis like quantum computers (or quantum teleportation hacked, although this would enrage theoretical physicists a bit) or just supercomputers or immense combined computational power. Because this is the most important economic and military factor, the uncertainty is immense. And it would be interesting to know because almost all private and commercial traffic is secured in one of these ways too. Let´s be surprised.

A wiki walk can be as refreshing to the mind as a walk through nature in this completely overrated real-life outside books:
https://en.wikipedia.org/wiki/Encryption
https://en.wikipedia.org/wiki/Deciphe...

[Jim · Rating 5 out of 5]

The Code Book is like geek porn. Explanations of the theories behind cryptography are woven together with anecdotes of times when code-making or code-breaking was integral to historical events. Singh strikes an excellent balance with this book. The clarity of his writing makes the explanations of the mathematics of cryptography very straightforward without dumbing them down, and the historical connections are always fascinating.

Personally, my favorite part was the section devoted to the role cryptography played in World War II. The cracking of the Enigma at Bletchley Park was probably one of the greatest moments in nerd history.

If you're fascinated by puzzles, curious about history, or you want to know what privacy really means in the 21st century, pick up this book. You'll have a hard time putting it down.

[Bradley · Rating 5 out of 5]

Coming on 20 years after the book was written, it’s still quite awesome despite all our subsequent advances in cryptography.

Or rather, I should say, we’re still living in the same world already transformed by pretty good encryption. The methods for breaking the security still falls in the same category as usual: interception. Of course, the means of interception has gotten amazingly good and creative as hell, but that isn’t the primary scope of this book.

Rather, it’s about an awesome crash course in the history of encryption from the Middle Ages or earlier, say Roman or Greek, all the way forward to mechanical solutions a-la Babbage and right into the thrilling good stuff of WW2, including Turing and the awesome Code Talkers.

The advances since then are almost stunningly fascinating, however, and aside from Zimmerman’s courageous advent of PGP, the REST of the story may well be trapped under National Security blankets still.

Alas. What I wouldn’t give to get a backstage pass to those goings-on. :)

Well written, accessible, and rather thorough, this book remains one of the best books on encryption for laypersons. Highly recommended.

[Richard Derus · Rating 2 out of 5]

PEARL RULED (p79)

The development of the telegraph, which had driven a commercial interest in cryptography, was also responsible for generating public interest in cryptography. The public became aware of the need to protect personal messages of a highly sensitive nature, and if necessary they would use encryption, even though this took more time to send, thus adding to the cost of the telegram.

When I awoke from my coma, I realized: 1) sesquipedalian verbiage needs must be read while fresh and hale, 2) I don't care as much as I thought I would, 3) hot Spring afternoon sunshine feels good.

Also, I might not be as smart as I thought I was. The graphs and tables preceding this page caused me to whimper and curl into a fetal ball. Ahead (I peeked) were *entire*pages* of comma-separated numbers. That is unconscionable. It is a replay of Tau Zero, the SF novel with equations in it, that I could not even bring myself to hurl at a wall I was so paralyzed by outraged betrayal at picking up a novel to discover EQUATIONS in it.

Keep your filthy math out of my fiction!

Anyway, this book. It's non-fiction so there's no reason to be sniffy about numbers and junk, right? Sorta right. I need something to give me the will to drag myself over the glass shards atop the bed of coals and in this read there wasn't anything at stake from moment to moment. Overall, yes; secrecy/privacy is a major part of the online world both in its presence and absence. But in this book the stakes are abstract and waaaaaaaaayyyyyyyyy above my li'l punkin haid.

I'll keep it in case it calls to me this winter. Now, no.

[Belhor Crowley · Rating 5 out of 5]

By far the best and the most interesting book on the subject. recommended to anyone interested in Cryptography and its history. I read it in three days mainly because I couldn't put it down.

[Annie · Rating 5 out of 5]

I haven’t had this much gleeful delight in a book in a long time. This book is pure fun. It’s not fast reading necessarily, and requires some active engagement to keep up, but man, it is a blast. If you read a lot of spy books as a child, or if you’re secretly jealous when there’s a cipher to be solved in a TV or movie plot and a character says,“Yeah, I can totally crack this if I have a few hours, let me get to work,” you’re going to love this.

Singh introduces us to famous historical ciphers and codes, as well as the basic principles underlying code making and code breaking- you actually get a fairly solid foundation on understanding how to build and crack most classic ciphers.

--------------CODES AND CIPHERS--------------

Some examples of interesting codes this book unpacks and deconstructs with you:

-Transposition. Substitution. Superencipherment.

-Caesar shift ciphers.

-The Vigenere square cipher.

-The Great Cipher of Louis XIV.

-The as-yet-unsolved Beale cypher.

-The ADFGVX cipher.

-The Zimmerman telegraph cipher.

-The one-time pad cipher (aka a Vigenere cipher where the keyword is a random string of letters, at least as many as are in the text to be enciphered- which is inherently un-decipherable by cryptanalysis. But which of course requires both the message writer and receiver to have a copy of the random key, which makes it vulnerable to discovery. Plus it’s expensive to constantly create brand-new random keys for hundreds of messages a day).

-Navajo code-talking.

-All the way on up to quantum cryptography, which in theory at least is an uncrackable cipher.

---------------CRYPTANALYSIS---------------

For me, the real genius comes into play here, in cryptanalysis- the deciphering of all those nasty little devils. Some memorable moments in cryptanalysis history:

-Al-Kindi’s method of deciphering by analyzing the message in terms of letter frequency, or looking for unusual letter pairings (in English, Q is basically always followed by U so if you find a particular letter that is never followed by anything but another particular letter, that’s probably Q and U).

-Bazeries’ method of deciphering the Great Cipher of Louis XIV by analyzing by syllable frequency rather than letter.

-Charles Babbage (who, incidentally, invented the prototype of a computer way back in the 1700s) invented a method of deciphering the Vigenere cipher. First, you look for repeated sequences of letters- words that are repeated, and which happened to have gotten encrypted the same way because they land on a multiple of the number of letters the key has. You count the spaces in between those words, and draw up a chart with all the different repeated word sequences and the factors that go into those spaces (e.g. factors of 20 would include 1, 2, 4, 5, 10, and 20- but you wouldn’t use just 1 letter for a keyword, so it can’t be that). Find the number that's a factor common to ALL of the repeated letter sequences, and you know the number of letters in the key word. Then you look at the letters the first letter of the keyword would be used to encrypt and use frequency analysis on *that*. [I’m not explaining this well, but Singh does, and it’s so brilliant it makes your ears wiggle.]

-The deciphering of the ancient script known as Linear B by Alice Kober and Michael Ventris.

-------------MODERN CRYPTOGRAPHY-------------

Cryptography can basically be credited with the invention of computers. Furthermore, cryptographers are the reason you can send encrypted messages that nobody but the receiver can access, and the reason you can buy things over the Internet without people taking you credit card information.

I have a BlackBerry, so I feel like I’m supposed to be a slick techie who knows what encryption is, but I’ve never heard it explained as straightforwardly as this book:

Alice wants to send Bob a letter and she doesn’t want the postal service workers to be able to read it. Obviously, she can’t just send it in a padlocked iron lock-box, because she has no way of securely giving Bob a key. So what can she do? She puts the letter in the iron box, padlocks it, mails it to him. He puts his own padlock on it- the box now has two padlocks- and sends it back to her. Now Alice removes her own padlock and sends the box, locked with Bob’s own padlock, back to him. He removes his padlock and reads the letter. That way, the box is never unlocked, but Alice and Bob don’t have to find a way to exchange keys. (This would be especially problematic if the key has to be different for every message or device, the way it is in technology).

Then there's the asymmetrical public key encryption system designed by Diffie, where Alice has a “public key” that allows anyone to encrypt a message to her, but cannot be decrypted by the same key- it can only be decrypted by another key, the private key to which only Alice has access. So Bob could “look up” Alice’s public key, which is known to everyone, encrypt his message to her, and she can decrypt it. In the padlock scenario, this would mean Bob would go to the post office, take an “Alice padlock,” of which there are many copies, lock the box with his message inside, and mail it to her. Only Alice holds the key that can unlock this, so the system is secure.

---------------CONCLUSIONS---------------

This is just such a cool book, an absolute ride. I can't imagine anyone who wouldn't have at least a little fun with it. It's accessible, it's interesting, it's challenging, and it's an unusual read. Not a bad thing to say about this one.

[Shafaet Ashraf · Rating 5 out of 5]

প্রায় ৩মাস ধরে পড়ে শেষ করলাম যেকোনো সিনেমাকে হার মানানো ক্রিপ্টোগ্রাফির ইতিহাস। এই বইয়ের সত্যিকারের মজা নিতে হলে ক্রিপ্টোগ্রাফির প্রটোকলগুলো বুঝে বুঝে পড়তে হবে, তবে সেগুলো বুঝতে জটিল কোনো গণিত জানার দরকার হবে না, লেখকের দক্ষতার পরিচয়টা সেখানেই।

পৃথিবীতে বড় বড় সব যুদ্ধগুলো হয়েছে আসলে 'কোডব্রেকার' আর 'কোডমেকার' দের মধ্যে, যারাই প্রতিপক্ষের পাঠানো গোপন চিঠিগুলো পড়ে ফেলতে পেরেছে তারাই কৌশলগত দিক থেকে একধাপ এগিয়ে গিয়েছে। সেই জুলিয়াস সিজারের সিজার সাইফার থেকে শুরু করে নাৎসিদের ব্যবহৃত এনিগমা মেশিন, আধুনিক কালের পাবলিক-কী এনক্রিপশন, কোয়ান্টাম ক্রিপ্টোগ্রাফির বিবি৮৪ এনক্রিপশন সবকিছু নিয়ে আলোচনা করা হয়েছে এই বইয়ে।

যদি মনে হয় যে খটমটে গণিত নিয়ে এই বই তাহলে ভুল হবে, এই বই ক্রিপ্টোগ্রাফির ইতিহাসের, কিভাবে মানুষের ইতিহাসের গতিপথে ক্রিপ্টোগ্রাফি বিশাল ভুমিকা রেখে চলেছে তাই নিয়ে এই বই।

[Stefan Kanev · Rating 5 out of 5]

I recently watched The Imitation Game, which left such a bad taste in my mouth, that I wanted to clean it up with something in a similar subject. Having read two of Sighn's other books, I picked this one.

I had high expectations and it met them nicely. The book tells the story of ciphers and encryption through history – from what the Greek and the Romans did, through the Enigma, and finally to RSA. The style is very easy and pleasant to read, everything is pretty understandable even if you don't have a math background (sometimes to the point of being slightly inaccurate) and there are a lot of interesting stories inbetween.

This book has a single downside – it's so pleasant and easy to read, that you'll be done with it in no time. Highly recommended.

[Arnab Paul · Rating 5 out of 5]

পড়ে শেষ করলাম Simon Singh এর The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography
বইটির সন্ধান পাই গুডরিডস ঘাঁটাঘাঁটি করতে করতে। Cryptography;অর্থাৎ আপনার তথ্যকে সর্বসাধারণের আড়ালে রেখে সংরক্ষণ ও প্রাপককে সরবরাহ করার বিদ্যা নিয়ে এই বই।হাজার বছর আগের রাজা বাদশাদের আমল থেকে Cryptography-র চর্চা শুরু,যার স্রোত এখন আপনার সোশাল মিডিয়া অ্যাকাউন্ট থেকে সেলফোনের রিচার্জ কার্ডের ব্যবহারে চলছে সদর্পে !চারশো পৃষ্ঠার এই বইটিতে Cryptography-র রোমাঞ্চকর ইতিহাস , বিকাশের রাজনীতিক পটভূমি ছাড়াও এর গাণিতিক সৌন্দর্যের সুখপাঠ্য বর্ণণা আছে।গণিতের অংশগুলো খটমটে নয় মোটেই, উচ্চ মাধ্যমিক পর্যায়ের বিন্যাস-সমাবেশ,সংখ্যাতত্ত্বের সাধারণ ধারণা থাকলেই যথেষ্ট।
বইয়ের শুরু রাণী এলিজাবেথের হাতে স্কটিশ রাণীর Encryption-সংক্রান্ত ফ্যাসাদে পড়ে করুণ মৃত্যুদণ্ডের কাহিনি দিয়ে, শেষ হয়েছে ভবিষ্যতের প্রযুক্তি Quantum Cryptography সম্ভাবনায়।
প্রাচীনকালে রাজা বাদশারা শত্রুরাজ্য পার হয়ে মিত্রের কাছে গোপন খবর পাঠাতে Cryptography-র আশ্রয় নিতেন।শুরুতে চর্চাটা ছিলো শুধু লুকানোতে, অর্থাৎ Steganography. স্পাই-এর মাথা কামিয়ে সেখানে মেসেজ লিখে চুল গজানোর পর পাঠানো হত, শত্রুর হাত থেকে তথ্য বাঁচাতে।খোলস অবিকৃত রেখে সেদ্ধ ডিমের সাদা অংশে লেখার পদ্ধতিও আবিষ্কার তখনি!পুরো বই জুড়েই 'কথা-লুকানো' বিদ্যার দুর্দান্ত সব কাহিনি,
পাশাপাশি তা থেকে তথ্য বের করার কৌশল এর কথা । বাৎস্যায়ন তাঁর কামসূত্রেও উল্লেখ করে গেছেন এর কথা,নারীদের জন্য নির্ধারিত ৬৪ কলার ৪৫ নম্বরে আছে এই বিদ্যা,"ম্লেচ্ছিকা-বিকল্প"!
ঐতিহাসিক সেকাহিনি, Code maker ও Code breaker দের যুদ্ধ। প্রথমদিকে চলত বর্ণের প্রতিস্থাপন এর মাধ্যমে Monoalphabetic Encryption ,মানে নির্দিষ্ট সংখ্যক অক্ষর শিফ্‌ট করা; a এর জায়গায় d ,b -র বদলে e এভাবে। এনিয়মে এক বর্ণ শিফট করে "ANT" কে লিখতে হবে "BOU"। অর্থাৎ ইংরেজি ছাব্বিশটি অক্ষর একে একে শিফট করে টেস্ট করলেই বেরিয়ে আসবে আসল মেসেজ।দিনে দিনে Cryptography
কঠিন হতে লাগলো। Code maker-রা বর্ণ প্রতিস্থাপন এর পরিবর্তে Randomly বর্ণ নির্ধারণ করলেন এবারে।অর্থাৎ প্রেরক ইচ্ছেমতো বর্ণ ধরবেন,যার এক কপি থাকবে প্রাপকের কাছে।এবারে সহজে মেসেজ বের করার পদ্ধতি আর চলছেনা।
কিন্তু মানুষের বুদ্ধিচর্চার Legecy টা এখানেই, পরিসংখ্যান বিশ্লেষণের মাধ্যমে সেই টেক্সটও পাঠের পদ্ধতিও বের করলেন Code breaker-রা। প্রতিটা ভাষার ধ্বনিতত্ত্ব বিশ্লেষণ করলে দেখা যায়,এখানে সুনির্দিষ্ট কিছু ধ্বনি বেশি ব্যবহৃত হয়।যেমন ইংরেজিতে সবচে' বেশি ব্যবহৃত হয় "e",তারপর "a","t" ইত্যাদি।এভাবে বর্ণ বের করার পদ্ধতির নাম Frequency Analysis. আরবেরা এই পদ্ধতির জনক।ধর্মগ্রন্থে কোন কোন শব্দ কতোবার ব্যবহার
হয়েছে, এই চর্চার মাধ্যমে পদ্ধতিটির আবিষ্কার(আল-শব্দটা বেশি ব্যবহার হয়,তাই‌ সংশ্লিষ্ট ধ্বনিগুলোর বাহুল্য থাকবে এখানে)।
এবার একটা সাধারণ পদ্ধতির কথা বলছি। একটা ইংরেজি Encrypted Text ধরে নিন। আলোচ্য পদ্ধতিটির সাহায্যে কোন বর্ণ বেশি ব্যবহৃত হয়েছে,তার একটা হিসেব করে আমরা "e" কোনটা বের করে নিতে পারি।স্যাম্পল হিসেবে Text থেকে বেছে নিচ্ছি তিন অক্ষরের এমন একটা শব্দ, যার শেষে ঐবর্ণটি অর্থাৎ যার আড়ালে লুকায়িত "e" আছে। এবার দেখবো দ্বিতীয় অক্ষরটিকে। পুরো Text এ যদি "e" এর পরে
ঐ দ্বিতীয় অক্ষরটি না দেখা যায় তাহলে নিশ্চিতভাবেই বলে দেয়া যায়,অক্ষরটি "h" এবং শব্দটা "The". পুরো ইংরেজি ভাষায় খুব বেশি শব্দ নেই যেখানে "e" এর পর "h" বসে।এভাবে ঐ বর্ণগুলো প্রতিস্থাপন করলেই আসল মেসেজের চেহারা বের হতে শুরু করবে।বাকিটা ভাষাবিদদের কাজ।বইয়ে পুরো এক অধ্যায় জুড়ে ধাপে ধাপে একটা গুপ্তবার্তা বের করে দেখানো হয়েছে,যা কোনভাবেই রহস্যোপন্যাসের কাহিনিজট ছাড়ানো থেকে চেয়ে কম নয়।
ছোটবেলায় এডগার এলান পো'র The Gold Bug এ এরকম পদ্ধতিতে গুপ্তধন বের করার কথা পড়েছিলাম,যদিও তখন কিছু বুঝিনি।ঐ অধ্যায়টা পড়ার পর পুরোনো প্রশ্নের উত্তর পেয়ে চমৎকৃত হয়েছি!
চার্লস ব্যবেজ ও স্যার হুইটস্টোন(সার্কিটের Wheatstone Bridge-খ্যাত) এরকম Cryptanalys এ সুপারদর্শী ছিলেন।তাদের এক মজার ঘটনা না উল্লেখ করলেই নয়। ভিক্টোরিয়ান ইংল্যান্ডে প্রেমিক-প্রেমিকার অবাধ ভালোবাসার আদান প্রদানটাকে ঠিক সহজভাবে নেয়া হতোনা।পরিবারের কেউ যেন না জানতে পারে,তাই পত্রিকার ব্যক্তিগত কলামে Encryption এর মাধ্যমে প্রেমপত্রের আদান-প্রদান হবার ট্রেন্ড চালু হয়েছিল তখন!
স্যার হুইটস্টোন একদিন The Times পত্রিকায় অক্সফোর্ডের এক ছাত্রের প্রেমিকাকে লেখা চিঠির পাঠোদ্ধার করেন,দেখেন সেখানে লেখা পালিয়ে বিয়ে করার কথা।পরের সংখ্যায় ঐ একই Encryption মেথড-এ তিনি বুঝিয়ে সুঝিয়ে লেখেন;দেখ বাবা,এভাবে পালিয়ে বিয়ে করাটাতো ঠিক না।পরের সংখ্যায় প্রেমিকা বেচারি সোজা-সাপ্টা ইংরেজিতে লিখে বসেন ,"Dear Charlie, write no more.Our cipher is discovered." !
এভাবে অসংখ্য রকম ধাঁধা তৈরি ও ভাঙানোর ঘটনা ইতিহাসে জ্বাজল্যমান।হাতে কলমে লেখার ব্যাপারটা উঠে গেল রেডিয়ো-যোগাযোগ ব্যবস্থার আবিষ্কারের মাধ্যমে। Cryptography-র সবচে' গুরুত্‌বপূর্ণ অধ্যায় শুরু হয় প্রথম বিশ্বযুদ্ধ শুরু হলে পরে।জয় পরাজয় নির্ধারণে গুপ্তবার্তাই হয়ে দাঁড়ায় প্রধান নিয়ামক।আমেরিকা ও ব্রিটেন Cryptography-র দৌড়ে তখনও এগিয়ে,এর মাধ্যমেই বিজয় ত্বরান্বিত হয়।কিন্তু দ্বিতীয় বিশ্বযুদ্ধে জার্মানবাহিনি নামে
দুর্লংঘ্য "Enigma" নিয়ে। সে সময়কার রোমহর্ষক ইতিহাসের শ্বাসসরুদ্ধকর বর্ণনা আছে বইটিতে।সে ইতিহাস শীতল স্নায়ুযুদ্ধের,মর্মান্তিক ও একই সাথে চূড়ান্ত উত্তেজনাকর।ঐ সময়টাতেই Cryptography-র বিকাশটা হয় সবচে' বেশি। ততদিনে Cryptography-টা আর ভাষাবিদদের মধ্যে সীমাবদ্ধ নয়,বরং গণিতবিদ,দাবাড়ু,বিজ্ঞানীদের প্রাধান্যে এগিয়ে চলছে দ্রুতগতিতে।অপ্রতিরোধ্য "Enigma"কেও হার মানান Bletchley Park
এর বিজ্ঞানী,গণিতবিদেরা,যার অন্যতম নায়ক অ্যালান টুরিং! তিনিই প্রথম কম্পিউটারের রূপকার, মেকানিকেল ডিভাইসের মাধ্যমে এর তৈরি।পরবর্তীতে তার উন্নয়ন করা হয় ভ্যাকুয়াম টিউব ব্যবহার করে।কীভাবে পর্যায়ক্রমে যান্ত্রিক কাঠামো থেকে তাড়িতিক রূপ লাভ করে কম্পিউটার, ঐ অধ্যায়ও পড়লেই ধরা যায় স্পষ্ট। আরো আছে আদিম মিশরীয় ভাষা হায়ারোগ্লিফিক রহস্যভেদের কাহিনি।
আপনার ইমেইল,ফেসবুক অ্যাকাউন্ট কতোটুকু সুরক্ষিত? আন্তর্জাতিক নিরাপত্তা সংস্থাগুলো নজর রাখছে কি? USA-র National Security Agency(NSA) ওখানকার সফটওয়্যার কোম্পানিগুলোর প্রতি নি্যম আরোপ করেছে, বহির্দেশে বিক্রিত সফটওয়্যারের সিকিউরিটি যেন এমন না হয় যে,তারা তা Break করতে না পারে!এর পক্ষে তারা যুক্তি হাজির করে টেররিস্টচক্রের চক্রান্ত-পূর্বাভাস পাবার অজুহাত দেখিয়ে।যদিও নথি ঘেঁটে দেখা যায়,
অনেক সময়ই ক্ষমতাধর প্রেসিডেন্টরা এই আড়িপাতাকে ব্যবহার করেছেন বিপক্ষদলের দূর্বলতাকে অস্ত্র হিসেবে পেতে।সেক্ষেত্রে ব্যক্তিগত নিরাপত্তার প্রশ্নে আমাদের মতো দেশের মানুষের অবস্থানটা তাহলে কোথায়?
ইতিহাস,বিশ্বারাজনীতি,গণিত,প্রযুক্তিপ্রেমিদের জন্য অবশ্যপাঠ্য এই বই।

[Pallavi Gambhire · Rating 5 out of 5]

I never thought I'd love a book about mathematics, or ever see the beauty of mathematics. My mother was definitely right when she kept pestering me to work harder on my math and argued that it was EVERYWHERE! (I had argued back saying I would be fine as long as I could perform the basic calculations!)
Maybe this is what growing up is about!
That being said, this is a very informative book about the past, present and future of cryptography. Singh takes us on a journey from ancient times where simple communications and hence simple codes sufficed, through a series of unfortunate events that resulted in the execution of Mary, Queen of Scots,to a time in the future when quantum cryptography might prevail. My favorite part is when he talks about the decipherment of Linear B (which led me to another amazing book of the same name), an ancient language discovered in the remains of a palace in Crete. Oh, and he also makes the Second World War seem interesting in an entirely differently way.
Singh has a knack for explaining ideas and theories, which might seem mundane if explained by someone else, in a very interesting manner. His use of characters called Alice,Bob and Eve to explain the codes, made it easy for a layperson like me to understand the theory behind them.
He even adds a few ciphers for us to decipher at the end. I must admit I skipped over those pages, but might return to them at some point in the future.
I recommend this book to anyone who is fascinated by ancient history, linguistics, cryptography, quantum physics, OR MATHEMATICS!

[Shoti · Rating 3 out of 5]

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[Gorab · Rating 5 out of 5]

⭐⭐⭐⭐⭐
This turned out to be a mine of knowledge for me.

What I learnt:
1. Difference between cryptography, steganography, ciphers, encryption and decryption

2. Various ciphers and their detailed techniques - Monoalphabetic, Caesar shift, Vigenere, Pigpen, Playfair, EDLSs, Morse Code, Beale Cipher…

3. Deciphering the ancient Egyptian and Greek texts - Hieroglyphics - how Linear B was decoded, and why Linear A is still a puzzle waiting to be solved.

4. Standardization of encryption - today's popular encryption mechanisms - DES and RSA

5. Future with quantum computing - explanation is crystal clear to help someone who is new to quantum mechanics.

6. Most interesting part - knowing and understanding all the great persons involved in making and breaking the code.

7. Details on the never ending race between non-breakable code and mechanism to defy all encryption.

8. Interesting background stories - Mary Queen of Scots, Man in the Iron Mask, Arab's frequency analysis, Creation (and breaking) of German Enigma, Bletchley Park, Navajo code, Rosetta stone, Zimmermann's PrettyGoodPrivacy, formation of laws "against" strong encryption.

8. A whole load of many more interesting concepts

If not for world war and the quest to decode the enemies thoughts, we wouldn't have the luxury of computers way ahead of its time.
Whether the same will be true for Quantum computers? I think so…

Interesting quotes:
"Cryptography used to be an obscure science, of little relevance to everyday life. Historically, it always had a special role in military and diplomatic communications. But in the Information Age, cryptography is about political power, and in particular, about the power relationship between a government and its people. It is about the right to privacy, freedom of speech, freedom of political association, freedom of the press, freedom from unreasonable search and seizure, freedom to be left alone."

"The fundamental question is whether or not governments should legislate against cryptography. Cryptographic freedom would allow everyone, including criminals, to be confident that their e-mails are secure. On the other hand, restricting the use of cryptography would allow the police to spy on criminals, but it would also allow the police and everybody else to spy on the average citizen."

"The deciding factor will be whom the public fears the most - criminals or the government"

As Neil Bohr said - "Anyone who can contemplate quantum mechanics without getting dizzy hasn’t understood it."

"The urge to discover secrets is deeply ingrained in human nature; even the least curious mind is roused by the promise of sharing knowledge withheld from others. Some are fortunate enough to find a job which consists in the solution of mysteries, but most of us are driven to sublimate this urge by the solving of artificial puzzles devised for our entertainment. Detective stories or crossword puzzles cater for the majority; the solution of secret codes may be the pursuit of a few." - John Chadwick

Highly recommended stuff!

Recommended for: If you love treasure hunt, logical deductions, puzzles, anything related to digital privacy sounds fascinating to you, then this is the book for you.
Not recommended: If you totally abhor simple mathematics, data interpretation, tables and charts.

[John Meo · Rating 5 out of 5]

This is a fascinating introduction to the world of cryptography. It has opened my eyes to a whole new subject that interests me, and now I have spent many hours attempting to create a machine that can decrypt hidden messages. It is a wonderful and gripping tale of the history of cryptography, and presents the entire plot as a battle between the code makers and the code breakers. I was never left a little bored at parts as I occasionally am during non-fiction books because it is a continuous story that flows throughout the pages. It keeps you in suspense over the fate of the queen of Scotland, the behind-the-scenes intelligence conflict in the midst of World War II, and the secret of the Beale treasure. For anyone interested in the matter, it is a must read, and for anyone who think they might enjoy the subject, I highly suggest it.
The history contained in this near-novel doesn't merely end a long time ago, but extends up to the very present, and discusses the exciting possibilities of cryptography in the future. Quantum computers and qubits enter the scene, hopefully presenting the holy grail of code-making, letting the code makers win the struggle forever. Our modern lives lay on the foundation of the public and private key system, including everything from the internet to checks. The only reason you are capable having your own private account in security is that complex math is occurring behind the scenes, multiplying two prime numbers hundreds of digits long so that any computer would take the lifetime of the universe to decode the messages you send. If you want to understand our modern age, you should definitely read this book.

[Hristina · Rating 4 out of 5]

Read for the Reading Without Walls challenge, for 'a topic you don't know much about'. And even though I didn't finish it in a week, CHALLENGE COMPLETE.

I really enjoyed The Code Book. The explanations were well-done, and the history lessons amazed me, which is odd because I'm not a history fan. I learned a lot about codes and ciphers and how they work, and that was the best part of it all. I liked the writing, so I think I might pick up another Simon Singh book in the future.

[Đoàn Duy · Rating 4 out of 5]

Trong lịch sử nhân loại đã xảy ra những cuộc chiến tranh tàn khốc, như hai cuộc thế chiến đầu thế kỉ 20. Tuy nhiên, bên cạnh những cuộc chiến bên ngoài chiến trường, thì ẩn bên trong nó lại là một cuộc chiến khác: cuộc chiến về thông tin. Đã có truyền tin thì tất nhiên cần phải có yêu cầu giữ bí mật. Thế là ngành khoa học mật mã (cryptography) ra đời để phục vụ cho yêu cầu đó.

Cuốn sách “Mật mã” (The Code Book) sẽ dẫn dắt chúng ta nhìn lại lịch sử dưới góc nhìn của mật mã học. Cuốn sách bắt đầu bằng những dạng mật mã đơn giản nhất ra đời từ cuối thế kỉ 16 và kết thúc ở cuối thế kỉ 20 bằng việc giới thiệu về ý tưởng mật mã lượng tử, một loại mật mã được cho là bất khả chiến bại dựa trên lí thuyết lượng tử.

Simon Singh (1964-?), tác giả cuốn sách, là tiến sĩ vật lí người Anh gốc Ấn Độ. Ông là một nhà khoa học tài năng và đã từng có nhiều đóng góp đáng kể trong việc phổ biến khoa học dưới nhiều hình thức: từ viết sách đến tham gia làm phim tài liệu khoa học. Ngoài cuốn The Code Book, trước đó ông còn là tác giả một cuốn sách khá nổi tiếng Fermat’s Last Theorem (Định lí cuối cùng của Fermat), và chính ông cũng là đạo diễn bộ phim tài liệu cho chuyên mục Horizon của BBC (chuyên mục nói về lĩnh vực khoa học công nghệ) về đề tài định lí Fermat này.

Cuốn sách The Code Book được Simon Singh trình bày rất dễ hiểu, bạn không cần phải lo cho dù bạn không thật sự giỏi về toán học, vì mỗi khi gặp một khái niệm toán học có vẻ lạ lẫm thì Simon sẽ dừng lại vài dòng, thậm chí cả trang sách, để giải thích nó rồi mới đi tiếp. Do đó chỉ cần bạn biết làm bốn phép tính cộng-trừ-nhân-chia cùng với một sự tò mò về thế giới mật mã là đủ để đọc cuốn sách.

Ban đầu, người ta chỉ nghĩ ra những loại mật mã đơn giản, đủ để che giấu nội dung thông tin. Kiểu như xáo trộn vị trí các chữ cái, hay là thay thế chữ cái này bằng một chữ cái khác, v.v.. Nhưng chẳng bao lâu sau thì những loại mật mã thế này đều bị các nhà giải mã phá được. Thế là có sự liên tục đổi mới trong cách tạo mã tạo ra một cuộc chiến trường kì giữa những nhà tạo mã và những nhà giải mã. Có người giải mã ra được thì bắt đầu nảy sinh tìm loại mật mã mới, và khi một loại mật mã mới ra đời thì các nhà giải mã lại phải lao đầu vào nghĩ cách hóa giải. Thậm chí người ta phải lập ra những đội ngũ chuyên nghiệp chỉ để làm công việc giải mã thông tin của đối phương.

Trong lịch sử mật mã học, có những bước ngoặt đáng kể đã góp phần không nhỏ trong việc quyết định lịch sử thế giới nói chung.

1. Máy Enigma

Bước ngoặt đầu tiên chính là việc cơ giới hóa việc tạo mã, bằng sự ra đời của hệ thống mật mã Enigma. Đây chính là vũ khí lợi hại nhất cũng như là nguyên nhân chủ yếu dẫn đến thất bại của Đức Quốc Xã trong thời kì thế chiến thứ hai. Chính cái máy Enigma này là nguồn động lực làm nảy sinh ra những ý tưởng đột phát về công nghệ trong thế kỉ 20. Ý tưởng vĩ đại nhất có lẽ thuộc về Alan Turing, người có công lớn nhất trong việc hóa giải máy Enigma, khi trong quá trình giải mã Enigma ông đã hình thành một ý niệm về một cỗ máy được gọi là Turing Machine – tiền đề cho sự phát minh máy tính sau này.

Ngoài ra, cũng vào thời kì thế chiến thứ hai thì lịch sử khoa học mật mã đã chứng kiến một loại mật mã bất khả xâm phạm đúng nghĩa của nó,. Đó là loại mật mã dùng ngôn ngữ của người địa phương Navajo đang sinh sống tại vùng đất Arizona ở Mĩ. Navajo là một bộ lạc rất nhỏ, và thổ âm Navajo là một dạng ngôn ngữ cực kì hiếm gặp, cả nước Mĩ ngoại trừ vài ba chục người là có nghiên cứu, ngoài ra nếu không phải là người Navajo thì trên thế giới chẳng một ai có thể hiểu nổi ngôn ngữ này. Người Mĩ đã dùng ngôn ngữ này cùng với những người Navajo biết tiếng Anh làm mật mã liên lạc, và họ đã có được một hệ thống mật mã tuyệt đối an toàn.

Như vậy có thể nói thế chiến thứ hai chính là cuộc chiến cân não giữa hai phe tạo mã và giải mã. Nếu như ngày đó, Alan Turing vì một lí do nào đó không thể hoàn thành sứ mệnh giải mã Engima của mình, thì có lẽ lịch sử thế giới đã rẽ sang một hướng khác.

2. Giải mã các văn tự cổ xưa

Một đỉnh cao trong lịch sử mật mã học cũng như khảo cổ học chính là việc giải mã những văn tự cổ xưa bao gồm những chữ tượng hình của Ai Cập cổ đại cũng như chữ Linear B nổi tiếng của Hy Lạp cổ đại. Chữ tượng hình Ai Cập cổ đại đã nhờ vào phiến đá Rosetta (Rosetta Stone, là phiến đá trên đó có chữ tượng hình Ai Cập kèm với chữ demotic và chữ Hy Lạp) làm cơ sở để giải mã. Jean-Francois Champollion là người đã hoàn thiện việc giải mã các chữ tượng hình này, và thành quả này của ông còn có một phần không nhỏ đóng góp của một nhà khoa học đa năng Thomas Young. Nếu như chữ tượng hình Ai Cập cổ đại còn có Rosetta Stone làm cơ sở giải mã thì chữ Linear B hoàn toàn không có gì. Dù vậy nó vẫn được giải mã bởi Michael Ventris, vốn là một kiến trúc sư, với sự góp sức của nhà nghiên cứu Hy Lạp cổ đại John Chadwick. Có thể nói việc giải mã được các văn tự cổ xưa đã cho thấy sức sáng tạo và tưởng tượng của con người dường như không có giới hạn, và đó cũng chính là một bước ngoặt khác trong lịch sử nhân loại trong việc khám phá lịch sử các nền văn minh cổ đại.

3. Phân phối chìa khóa mã

Trong khoa học mật mã, có một vấn đề cực kì quan trọng, mà mãi sau thế chiến thứ hai thì người ta mới tìm ra cách giải quyết triệt để nó. Đó chính là vấn đề phân phối chìa khóa mã. Muốn giải mã thì bắt buộc phải có chìa khóa, và làm thế nào để người nhận có được chìa khóa mã một cách an toàn nhất. Có lẽ chỉ có cách gặp mặt trực tiếp nhau, vì nếu trao đổi qua vô tuyến thì sẽ bị rò rỉ thông tin ngay. Hãy tưởng tượng bạn tạo ra mật mã để liên lạc với hàng ngàn người trên thế giới, và phải gặp mặt từng người để trao chìa khóa mã, thế thì sẽ phải tốn rất nhiều nguồn nhân lực và chi phí chỉ để phục vụ cho chuyện phân phối chìa khóa này. Như vậy với việc kinh tế phát triển, nhu cầu đòi hỏi bảo mật thông tin ngày càng cao với mật độ ngày càng lớn, thì việc làm sao phân phối chìa khóa mã một cách an toàn và hiệu quả nhất đã trở thành một bài toán nhức đầu khác cho giới khoa học mật mã.

Đã có một ý tưởng nhen nhóm lên cho việc giải quyết vấn đề này. Hãy tưởng tượng thông tin cần được gửi là bức thư đựng trong một hộp sắt, với ổ khóa chính là mật mã dùng để mã hóa bức thư, và chìa khóa mở ổ khóa chính là chìa khóa mã. Anh A giờ đây muốn đưa thông tin cho anh B thì phải tìm cách làm sao đưa luôn chìa khóa mã cho anh B mà không cần phải gặp mặt. Đặt trường hợp là nếu gửi chìa khóa qua bưu điện thì cơ may chìa khóa bị lọt ra ngoài là rất cao. Thế là A và B quyết định thế này: anh A dùng một cái hộp có 2 lỗ khóa để có thể khóa lại bằng 2 ổ khóa. Anh A bóp ổ khóa của mình lại, ổ khóa A, và giữ chìa khóa A cho riêng mình. Đưa sang anh B, anh B lại dùng ổ khóa của mình, ổ khóa B, để khóa cái hộp thêm lần nữa, và cũng giữ chìa cho riêng mình, rồi gửi về lại anh A. Anh A thấy lúc này cái hộp đã được khóa tới 2 ổ khóa, nên đã lấy chìa của mình mở ổ khóa A, xong rồi gửi sang anh B. Lúc này cái hộp còn lại duy nhất một ổ khóa mà chỉ anh B mới mở được, nên cho dù cái hộp bị đánh cắp thì người ta cũng chẳng tài nào mở nổi. Và anh B chỉ việc lấy chìa của mình mở ổ khóa B rồi đọc thư.

Tuy nhiên, ý tưởng là thế, nhưng trong khoa học mật mã nếu áp dụng đúng như vậy thì sẽ nảy sinh một vấn đề khác thuộc về logic: đó là trình tự giải mã. Cái hộp có 2 ổ khóa, mở ổ nào trước đi nữa thì cái hộp cũng được mở ra. Nhưng một văn bản được mã hóa cần phải được giải mã theo trình tự “vào trước-ra sau”. Tức là nếu văn bản được mã hóa 2 lần thì người nào mã hóa sau cùng sẽ phải giải mã nó đầu tiên nếu muốn bức thư hoàn toàn được giải. Trở lại câu chuyện lúc nãy, vì anh B mã hóa bức thư cuối cùng nên anh B phải giải mã bức thư ra đầu tiên, rồi đưa anh A giải mã lần nữa thì bức thư mới có thể đọc được, nhưng anh B mới là người cần đọc bức thư, nên nếu làm vậy thì khi bức thư được giải mã hoàn toàn thì nó lại ở chỗ anh A, như vậy thì cũng vô dụng.

Dù ý tưởng có điểm không logic như vậy, đó chính là động lực cho các nhà khoa học mật mã đi tìm lời giải. Ở khúc này có một chi tiết cực hay liên quan đến việc tạo mã, chính chi tiết này đã giúp cho người ta vượt qua được sức ì tâm lí bao lâu nay để giải quyết được vấn đề phân phối chìa khóa mã. Từ đó hình thành loại mật mã mới khác, đuợc cho là không thể phá vỡ, vào cuối thế kỉ 20: mật mã RSA.

4. Mật mã lượng tử

Tuy vào thời điểm cuối thế kỉ 20, RSA là mật mã cực mạnh rồi, nhưng người ta lại phải đối diện với nguy cơ nó sẽ bị phá vỡ. Lúc này, lí thuyết lượng tử bắt đầu đóng vai trò của nó. Sở dĩ mật mã RSA không bị phá nổi là vì hạn chế ở các máy tính, cho dù máy tính có phát triển kiểu tốc độ xung tăng gấp đôi sau 18 tháng thì cũng phải mất cả ngàn năm mới đủ mạnh để phá vỡ RSA. Thế nhưng với một máy tính lượng tử thì chỉ mất dăm ba phút. Để đối phó trước với sự xuất hiện máy tính lượng tử sau này, người ta bắt đầu nghĩ đến một dạng mật mã tuyệt đối, tức là mãi mãi không thể phá vỡ. Và khái niệm về mật mã lượng tử đã ra đời.

Có thể thấy ngành khoa học mật mã đã quy tụ rất nhiều lĩnh vực: từ toán học, đến ngôn ngữ học, và rồi lí thuyết lượng tử của ngành vật lí học cũng góp mặt vào. Không chỉ trình bày về những loại mật mã khác nhau qua từng thời kì, mà Simon Singh còn thông qua mật mã học để kể các câu chuyện lịch sử, những câu chuyện bên lề của những nhà khoa học thiên tài như Alan Turing, Thomas Young, Jean-Francois Champollion, Michael Ventris,v.v.. Do vậy đây hoàn toàn không phải là một cuốn sách khô khan toàn số với chữ cùng những công thức toán học này nọ. Trái lại những câu chuyện mang tính lịch sử trong cuốn sách sẽ khiến người đọc cảm giác như đang đọc một cuốn tiểu thuyết trong đó nội dung chính là cuộc chiến cân não giữa hai phe lập mã và giải mã.

Sài-gòn,
20100408

[Eric_W · Rating 5 out of 5]

Singh, author of Fermat's Enigma, has even included a code to practice one's deciphering skills on. The successful cryptanalyst will win $15,000. In the appendix, he discusses other famous attempts at breaking codes, including the recent book, The Bible Code, by Michael Drosnin. This work caused quite a stir a couple of years ago when Drosnin, building really on the work of several Hebrew scholars, claimed to have discovered several prophecies hidden in the text of the Bible, a forecast of the assassination of the Kennedys and of Anwar Sadat. The Biblical code was an EDLS (equidistant letter sequence) code, where you take any text, pick a particular starting letter and jump ahead a given number of letters to spell out a sentence.

As critics have pointed out, any large text will produce all sorts of things. Brendan McKay at the Australian National University used Drosnin's technique to search Moby Dick and discovered similar predictions of assassinations that have occurred. Hebrew texts, Singh notes, are particularly rich in EDLSs because Hebrew has no vowels, which means interpreters can insert vowels as they see fit. Codes are constantly evolving; as code breakers break them, new ones must be developed. The supposed one-time pads, as in the Cryptonomicon, even had weaknesses — for example, if used more than once or from patterns inadvertently created by typists, patterns being the entry into most ciphers. Cryptanalysis, or the process of code breaking, was really invented by Islamic scholars in the 19th century. Substitution ciphers, where another alphabet is substituted for the original, were believed to be unbreakable; there were so many possible combinations of 26 letters that it would take billions of years to test all of them.

The Islamic scholars, while analyzing the Koran, discovered that the frequency of letters was not the same. In English, for example, the letter 'e' appears much more frequently than 'z' By analysis of letter frequency and knowing the language of the cipher, deciphering became quite simple. Blaise de Vigeniere solved this weakness by inventing the Vigeniere square, which provided multiple cipher alphabets using keywords to link letters with particular alphabets, a polyalphabetic cipher. The beauty of his scheme was that the letter “e” might be represented by several other letters, so frequency became irrelevant C or so everyone thought. To decipher the code, all one needed was the keyword, easy to remember, and not necessary to write down anywhere. Deciphering was a tedious process, however, and his impregnable ciphering system was not widely used. The Great Cipher was created by a father and son team working for Louis XIV. Their system was to use a combination of various types of ciphers. Unfortunately, they died without recording how their cipher worked, and many documents in French archives remained completely unreadable until the late 19th century when a French cryptanalyst spent several years painstakingly applying his knowledge of ciphers to the problem. Several of the documents thus finally deciphered revealed the identity of the Man in the Iron Mask.

Charles Babbage, inventor of the modern calculator and computer, was the one who broke Vigeniere's polyalphabetic system, by using statistics to create an algorithm that helped reveal the keyword. The problem in the twentieth century has not been the development of undecipherable ciphers. The computer makes encoding very easy and quite unbreakable. But each ciphered message can only be deciphered using a key. The recipient has to know the key. Banks would hire messengers to deliver keys to encrypted messages that needed to be sent from one bank to another. That proved to be a bureaucratic nightmare, and as the Internet created a need for encrypted messages between individuals and online stores or other persons, the deliverer of the key became very important. Martin Hellman, Ralph Merkle, and Whitfield Diffie decided the problem was not insoluble. As Hellman said, “God rewards fools.”

Only a fool would be willing to work on a problem for which the experts had said there was no solution, and to be willing to keep getting excited by an idea only to have it flop, then try another. Their solution was unique. They eliminated the need for key exchange. Just how they did this is marvelous in its simplicity, but if I told you you wouldn't need to read the book, which is what I heartily recommend. PQP, the cipher made public so that anyone could use it, made the government nervous and civil libertarians and others in favor of privacy leap for joy. Now anyone could encrypt a message with total security. We hear constantly about the worry that the NSA, CIA, and others in government have about the easy ability of ordinary people to have a level of encryption that is indecipherable. But, of course, it=s in their interest to make everyone think they have an indecipherable message, so my guess is that those agencies already know how to break the unbreakable codes but just don't want anyone to know they can.

[Cindy · Rating 5 out of 5]

This is a *must* read before reading Cryptonomicon. Or maybe after, like I did.

If you at all feel uncomfortable in your knowledge of one time pad cyphers, public/private keys, or the importance of really good cryptography for average folks, please read this book! It's sadly a bit out of date, but Singh does such a brilliant job of methodically building up the complexity in cyphers though history, that you will inevitably learn a ton.

[Jason · Rating 5 out of 5]

i picked this up at my brother in law's house and started reading it, immediately went out and bought a copy....
wow...
what a FANTASTIC book...
mathematically oriented non-fiction that reads like an anthology of suspense stories...
highly enjoyable...

[Eirini Zazani · Rating 4 out of 5]

Πολύ όμορφο βιβλίο για την κρυπτογραφία και τους κωδικοθραύστες είτε αφορά αρχαίες γραφές είτε κατασκοπία ή οικονομία. Ο συγγραφέας έχει ερευνήσει πολύ και παραδίδει ένα επιστημονικό εγχειρίδιο του οποίου το θέμα, με αφηγηματικό ταλέντο, καταφέρνει να εκλαικεύσει. Υπάρχει στο βιβλίο πλούσιο οπτικό υλικό κι επεξηγηματικά παραρτήματα. Δυστυχώς, το βιβλίο αναφέρεται στην κρυπτανάλυση και το σπάσιμο των κωδίκων μέχρι το 2000, με αποτέλεσμα και κάποιες ιστοσελίδες που αναφέρει να είναι ανενεργές. Θα ήταν πολύ ενδιαφέρον να βλέπαμε την εξέλιξη της κρυπτογραφίας και τα επόμενα έτη. Συστήνεται ανεπιφύλακτα.

[Sajjad thaier · Rating 5 out of 5]

يمكن أعتبار هذا الكتاب هو أفضل مقدمة كتبت لغير المتخصصين فيما يخص موضوع التشفير والتعمية.
يتناول الكتاب أنواع وأساليب التشفير وإخفاء الرسائل والخطط العسكرية منذ عصور ما قبل الميلاد وحتى وقتنا الحاضر. في البداية يعرض الكاتب أقدم أساليب التشفير المسجلة وهي شفرة قيصر وهي أبسط أنواع التشفير التي يقوم المشفر بتحريك الأبجدية بعدد معين من المواضع مثل أبدا حرف الألف بالباء والباء بالتاء وهكذا وكلما تم كشف شفرة جديدة يتم تطوير شفرة أقوى على الكسر وهكذا كان المعركة طوال التاريخ بين المشفرين وكاسري الشفرات أو محللي الشفرات وقد لعبت الشفرات دوراً رئيسياً في تشكيل السياسة العالمية فكشف الشفرة التي كانت تستخدمها ماري ملكة اسكتلندا هو السبب الرئيسي الذي أدى إلى إعدامها وكذلك قيام البريطانيين بكسر شفرة الانيغما الالمانية قد كشف الخطط العسكرية الالمانية بشكل كامل أمام الحلفاء بل حسب بعض التعابير كانت الحرب الوحيدة في التاريخ الذي كان أحد الطرفين معرفة كاملة بكل تحركات خصمه.
أما الان فأن التشفير يشكل شيء محورياً في حياتنا حتى لو لم ندرك ذلك فالتشفير هو ما يوفر لنا ارسال واستقبال الرسائل بشكل سري ومن دون الاطلاع عليها من قبل طرف ثالث . وقد عانى أصحاب هذا المجال من المضايقات الشديدة من الحكومات التي لم تكن تريد لتقنية التشفير أن تنتشر بشكل واسع وكان ذلك في سبعينيات وثمانينيات القرن الماضي . لكن الطبيعة البشرية والرغبة بالحرية من دون رقابة تنتصر دائماً وابداً .

[Jen · Rating 4 out of 5]

I thought this book would be dry and boring, but oh no! I love a good puzzle, and this history of making, cracking, and innovating secret codes was enthralling. And it gets better ... at the end of the book there are codes to try your hand out. I got pretty excited when I solved the first (and easiest one). They got harder and the book became overdue at the library so I gave it up. For about a week I had the idea that I was going to be the best code cracker ever and that the CIA would HAVE to hire me and I would find the secret buried treasure in the hills of Virginia (or wherever). I even bought a book of New York Times crossword puzzles to exercise my brain, and I have since come to accept reality. I will probably never solve an entire crossword puzzle on my own (by the way, the Wall Street Journal is sooooo much harder than NYT--just looking at them makes me feel stupid), much less crack secret codes.

[Dan · Rating 5 out of 5]

The Code Book has wide appeal and is a good read for anyone who is of the polymath mindset. If you like history pertaining to computing or are interested in algorithms, it is a monumental book.

Singh may be the best science writer out there. He has that rare ability to take complex science and math topics and explain in very straightforward layman’s terms.

[Kat V · Rating 4 out of 5]

This is fascinating. What a fun and accessible way to break down codes and cyphers over the years! No math required on the part of the reader to understand, thankfully! The beginning was more interesting than the end but still really good overall. 4.1 stars

[Grace · Rating 3 out of 5]

3.5 rounded down

Interesting concept about the evolution of cryptography, but a little dry at times and overly involved. Definitely didn't feel as much geared towards the casual reader curious about cryptography but with no real interest in actual codebreaking themselves...

[Krycek · Rating 5 out of 5]

I was fascinated with codes and ciphers when I was a kid. I even had a "junior spy code kit" with a bunch of cool stuff and I could send little notes to friends with secret messages like "Mr. Nutzenjammer is a dork" and "Cindy eats her boogers" and we would all congratulate ourselves with our cleverness. That's all pretty juvenile, but the ciphers included in my little spy kit were the basics in modern encryption systems and you can read all about it in Simon Singh's The Code Book, an excellent primer for understanding encryption methods and a fascinating account of its development through history.

Amazingly, Singh has the ability to make this rather complex topic understandable as well as entertaining. I am by no means mathematically inclined, but Singh explains the processes involved in each cipher he describes through baby steps and multiple analogies. If one doesn't work for you then the next will until you get it. This book actually makes you feel like you're learning something. 

Nevertheless, some of the concepts are mind boggling. Imagine for a moment this number: 10^130. It's a huge number but can be factored by a computer in about 15 seconds. Now imagine the number 10^308, which is ten million billion billion billion billion billion billion billion billion billion billion billion billion billion billion billion billion billion billion billion times bigger than the number 10^130. It would take more than a thousand years for a hundred million personal computers working together to crack a cipher using a value such as this in its key, yet this is the scale of numbers that most modern banking encryptions use. As one might guess, these encryptions are pretty much unbreakable.

Things truly get weird when Singh describes the concept of quantum cryptography, which I won't try to describe but will just say that I re-read that section a couple of times. Although quantum cryptography was just in a conceptual stage at the time of The Code Book's publication, who knows? It might be in usage now. The Code Book was first published in 2000 and a lot has changed since then (probably more than we realize, considering the secretive nature of the topic). At any rate, Singh makes a good point that cryptography, while historically of vital importance in political intrigues, is now of vital importance to most of our daily lives since the internet, for better or worse, has basically connected the world. Because of internet banking and commerce, information security is of prime importance.

Singh also, however, does a good job of telling the stories of code makers and code breakers. Particularly interesting and moving is the story of the brilliant cryptanalyst Alan Turning who committed suicide after the war when attempts to "cure" his homosexuality drove him into a deep depression. However, Turing was one of those unsung heroes working in secrecy, without whom the Allies may very well have lost World War II. Singh's ability to weave these stories into the complex mechanics of cryptography make for an engrossing narrative and one that has excited my intellectual imagination like few others have.

So ditch the "junior spy kit." That's kid stuff. Read The Code Book and you will know how to send inter-office gossip with complete security.

[Julia Hughes · Rating 5 out of 5]

Mr Singh manages to explain concepts that should be way beyond this thickie's level of understanding. That he manages to do so in an entertaining page turning manner is testament to his skill both as a mathematician and a writer. This book examines how from earliest history in parallel with writing, it became necessary for human kind to devise ways to send messages in code. So we learn how complex codes developed from very simple ones, and Simon explains along the way that there are ancient codes still waiting to be decoded and we also learn how to identify when a code is actually being deployed. It seems the best codes are the simplest, but if you need to tell more than two people a code, like a secret, it becomes more vulnerable. Entwined with the stories of code, are the stories of people who throughout history have relied on those codes being unbreakable - in some cases paying with their lives (eg Mary Queen of Scot) when it this is proved not to be the case. We're all intrigued by codes - witness the popularity of newspaper coffee break pages which will usually include a codeword problem. This book is well illustrated, extremely readable and throws new light on an already fascinating subject.

[Thom · Rating 5 out of 5]

A history of codes and ciphers in context, with explanations and visuals. The only minor drawback is that it is 20 years old, and half of the "future speculations" are now commonplace - and less fully explained. Would happily read an update :)

Very accessible, and pushes the deeper math into the extensive appendices. The supporting materials are also excellent. The author published a series of codes in the book with a reward for breaking them, claimed a little more than a year after publication. Nice gimmick, but he also mentions others who have done the same (e.g. Martin Gardner). I would nominate this as THE reference book about codes if it were updated.

I somehow missed this book in the past, but after reading Singh's book on numbers in the Simpsons, I added this to my reading list - where it languished for more than six years. Do yourself a favor and don't wait that long. 4.5 stars.

[Nicolle · Rating 5 out of 5]

This is the second work of Simon Singh that I have read, and in my opinion it is the greater of the two. It explores the art of ciphering codes and encryption which has developed profusely over the centuries, with alot of help from Charles Babbage and the computer.

Singh delves into the story of Mary Queen of Scots and explains in an epic and intersting way about how Mary's life depended upon whether her encrypted messages were deciphered. It goes on to the key role of mathematicians in WWII particulatly the ones based in the England, who successfully decoded messages that the Germans sent to each other and it is said that without mathematicians we would've lost the war!

This is an engaging insight into the history of cryptography and a must read for any puzzle wizzes, mathematicians or historians.

[Lady Clementina ffinch-ffarowmore · Rating 5 out of 5]

Singh does an excellent job explaining the development and process of cryptography and cryptanalysis in easy to understand terms (except (for me) perhaps the working of the Enigma, which still is a bit of an enigma!)- in fact so easy does he make it sound that one might be tempted to believe that one can be a cryptanalyst oneself- well until on turns to practically solving problems anyway. I also liked the way he wove the explanations of the actual process and working of encryption and cryptanalysis with the history and stories of how they evolved and were used and finally broken. Another plus for me was his inclusion of ancient scripts and their decipherment. The book is both informative and thoroughly enjoyable! The one issue I had was with the edition that I bought in which some of the pictures were really dark and hard to see.