Summary of The Code Book by Simon Singh

BookSummaryClub Blog Summary of The Code Book by Simon Singh

Are you intrigued by puzzles and secret codes? Or have you tried to come up with your own secret code to use so that your messages don’t fall into the wrong hands? For most of us, the world of cryptography seems like it belongs to book, movies and those in the spy business. In reality, cryptography has been used almost from the very beginning of time in some form of the other. It was used mostly by those in power trying to keep their enemies in the dark regarding their plans. However, over time, it has begun to not only retain that purpose but begin to take on a whole new identity. 

So, how much do you know about cryptography? Do you know how it all began and how it has changed over the years? Or what about how it was used in wars and online? 

In this book summary, readers will discover:

  • The beginnings of cryptography
  • How cryptography evolved 
  • Advances made during times of war
  • The new age of cryptography

Key lesson one: The beginnings of cryptography

Cryptography refers to the act of concealing the true meaning of a message. It goes all the way back to the fifth century BC when the Greeks used it to secure communication whilst under threat from Persia. In its humblest beginnings, cryptography consisted of two components substitution and transposition. 

Transposition entailed the rearrangement of a sentence of the letters of a word to make a cipher. A cipher refers to a secret way of writing a message. Substitution refers to when one letter is actually a substitute for another. If all letters of the alphabet are used and each letter has a substitute, it is known as a cipher alphabet. Julius Caesar was known to use substitution and gave rise to the Caesar shift cipher whereby the standard alphabet was substituted by a letter a fixed number of spaces down. For example, if you shifted the alphabet by two places the A=C and B=D. This was a simple substitution cipher and did not take long for the enemies to crack. Thus, it evolved to keyword ciphers which were similar but were based on a keyword that was placed before the alphabet and eliminated the letters it contained from the said alphabet. 

As cryptography began to get more elaborate, cryptanalysts also began to emerge. They came up with effective strategies to crack codes and decipher messages. In 750 AD, Arab cryptanalysts developed frequency analysis – a cypher breaking tool that was extremely effective. It was based on the fact that every language uses some letters and words more than others. If you knew these letters and words, it was only a matter of time before you could crack the code. Thus as cryptanalysts became better at cracking codes, cryptography also had to make improvements to constantly stay ahead. 

However, up until the fifteenth century, very small changes were made to ciphers. It became pretty evident when Mary, Queen of Scots was executed due to conspiring to kill Queen Elizabeth. Her correspondence had been easily deciphered by Queen Elizabeth’s cryptanalysts. With royalty using ciphers that could easily be decoded, what hope was there for anyone else? 

Key lesson two: How cryptography evolved 

It was not until the sixteenth century that a new form of cipher emerged. Blaise de Vigenère, a Frenchman, developed the polyalphabetic cipher. This cipher differed from the previous one as it used 26 distinct cipher alphabets in one message. It involved making a Vigenere square with 26 rows and a codeword. Each row contained a cipher alphabet that move one place in relation to the alphabet above it. For example, if the first row contained CDEFG then the second row would be DEFGH. The codeword could then be used which alphabets are in use. He called it the unbreakable cipher. 

But the cipher was not unbreakable – it was just more secure. However, what it was was impractical and time-consuming. This means it was not used readily by those who relied on cryptography the most. The military, for example, needed something quick and simple that they could use easily. As time passed, more variations of the monoalphabetic cipher arose. In the seventeenth century, Louis XIV liked to use numbers to substitute syllables instead of letters. However, in the eighteenth century, a new problem arose – telegraph communication. In order for a telegraph to be sent, an operator had to read a message to deliver it. This was not ideal if you would want to send a secret message and ciphers needed to once again evolve. 

Key lesson three: Advances made during times of war

When World War I came around, it became clear that a secure and foolproof method was needed. The US military developed a system they called the one-time pad cipher. This system was basically a variation of Vigenere’s system and utilised two identical books. One book was used by the sender and the other by the receiver. Each page of the book contained a randomly generated 24 letter codeword. Once it is used, it is torn out of the book on both ends. This meant that each codeword was only used once. 

This system was proven to be unbreakable. However, it was not without problems. Firstly, the books were used up quickly. During the war, messages were rapidly sent throughout the day – sometimes reaching numbers of a hundred or more. Secondly, coming up with random codewords was not exactly easy and thirdly, getting the books to the parties involved was also difficult, to say the least. So, although the system was basically indecipherable, it was also impractical for use in war. 

Thus, a different system was needed. This was when German inventor, Arthur Scherbius made the Enigma. The Enigma was a mechanical device consisting of a keyboard, a display board and a unit made up of cipher discs. With this invention, cryptography entered the world of mechanisation. Users simply had to type a letter and the cipher discs determined which cipher letter would be displayed depending on their configuration. Scherbius’ invention was too late for World War I and only picked up traction when World War II started looming. The German military ended up purchasing 30 000 Enigma machines which was an incredible investment. The fact that they had so many made their encryption virtually impenetrable. 

When the British started coming across odd ciphers that the Germans were using, their cryptanalysts were stumped. Enigma was doing its job beautifully but that didn’t mean that it was unbreakable. It just took a bit longer for cryptanalysts to figure out. The Germans relied on two different keys to send their communications. There was a daily key used but each message started with a new key that was only applicable to that message. To avoid any errors the German would repeat the message key twice. This ensured that those receiving the message knew how to set the cipher discs. It was a Polish cryptanalyst, Marian Rejewski,  that noticed this repetition and began to focus on them. It took him a year to establish the different possible configurations of Enigma’s cipher discs. There were 105 456 possible configurations in total!

This is when Alan Turing and the team of cryptanalysts came in. Turing also analysed old messages like Rejewski did to identify any patterns. What Turing actually did to change the war was to mechanize the configurations that Rejewski identified. In doing this, he basically connected all Enigmas until the right combination revealed the key. This gave the Allied forces the upper hand in the war and is thought to not only have saved lives but also shortened the war. 

Key lesson four: The new age of cryptography

Enigma was the start of a new generation of cryptography and when computers emerged a new form of secure communication also emerged. As computers became popular and a necessity in businesses, security was needed. IBM stepped forward with a system named Lucifer. Lucifer translated messages into binary code, broke them into 64 pieces and then scrambled them 16 times. It became approved by the NSA as the Data Encryption Standard or DES. 

Then three cryptographers named Whitfield Diffie, Martin Hellman and Ralph Merkle came together to develop a way in which encrypted messages could be exchanged over large distances. Standard encryption worked in that the encrypted message was sent and the recipient would need the correct key to decipher it. However, unless they met in person, the key would have to be sent in some way and could be intercepted. The team came up with a new idea whereby the encrypted message is first sent to the recipient and then the recipient would further encrypt the message using their own key. After doing this, they would send it back to the sender who would then remove his encryption and send it back to the recipient so they could easily remove their own second encryption.

These techniques continue to be refined further and now the future of cryptography is dependent on advances in technology. The DES and RSA ciphers have held up as it is impossible to keep up with the sheer volume of data. The only thing that could possibly aid in its deciphering is quantum computers. However, cryptographers are also aware of this looming threat and are working to stay ahead. Thus, with new technological advancements and discoveries every year, the world of cryptography will also work to continuously improve keeping the art of cryptography alive in the modern world.

The key takeaway from The Code Book is:

Cryptography has aided man since the beginning of time. No matter the situation, if people were to remain in power they had to stay ahead of their enemies and prevent any important information from getting in the wrong hands. Thus cryptography has stayed alive throughout the years, evolving alongside mankind and their requirements. But just as cryptography has evolved, so too have cryptoanalysts. Modern cryptography has been transformed by technology and it will continue to improve throughout the years to come.

How can I implement the lessons learned in The Code Book:

Cracking codes requires resilience and patience. Just as crypto analysts stick to their ciphers and battle it out until it is solved, so too should you strive to look at problems with such patience and resilience. It is only through these characteristics that you can problem-solve effectively.

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