Summary of Simon Singh's The Code Book

Everest Media

Description

Please note: This is a companion version & not the original book.
Sample Book Insights:
#1 On October 15, 1586, Queen Mary 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, planned to prove that Mary was at the heart of the plot, and was therefore equally culpable and deserving of death.
#2 The plot to kill Elizabeth and replace her with Mary, a fellow Catholic, was discovered by Walsingham, the principal secretary. The challenge for him was to demonstrate a link between Mary and the plotters.
#3 The art of secret writing was used to save Greece from being conquered by the Persians in 480 B. C. 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. The Greeks began to arm themselves.
#4 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 sixteenth 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.

Sujets

• Catholicisme
• Linguistics
• General officer
• General

Informations

• Publié par: Everest Media LLC
• Date de parution: 27 avril 2022
• Nombre de lectures: 0
• EAN13: 9781669393948
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Insights on Simon Singh's The Code Book
Contents Insights from Chapter 1 Insights from Chapter 2 Insights from Chapter 3 Insights from Chapter 4 Insights from Chapter 5 Insights from Chapter 6 Insights from Chapter 7 Insights from Chapter 8
Insights from Chapter 1

#1

On October 15, 1586, Queen Mary 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, planned to prove that Mary was at the heart of the plot, and was therefore equally culpable and deserving of death.

#2

The plot to kill Elizabeth and replace her with Mary, a fellow Catholic, was discovered by Walsingham, the principal secretary. The challenge for him was to demonstrate a link between Mary and the plotters.

#3

The art of secret writing was used to save Greece from being conquered by the Persians in 480 B. C. 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. The Greeks began to arm themselves.

#4

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 sixteenth 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.

#5

The aim of cryptography is not to hide the existence of a message, but rather to hide its meaning. To render a message unintelligible, it is scrambled according to a particular protocol that is agreed beforehand between the sender and the intended recipient.

#6

Cryptography can be divided into two branches, called transposition and substitution. In transposition, the letters of the message are simply rearranged, which effectively generates 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.

#7

Transposition is another form of encryption. It is when a message is written along the length of a wooden staff, and then the strip is unwound, which reveals a list of meaningless letters. The message has been scrambled. To recover it, the sender's scytale must be used.

#8

The first documented use of a substitution cipher for military purposes was by Julius Caesar, who sent a message to Cicero, who was besieged and on the verge of surrendering. The substitution replaced Roman letters with Greek letters, rendering the message unintelligible to the enemy.

#9

The Caesar shift is a method of encryption that involves substituting each letter in the plain alphabet with a letter from a cipher alphabet, and the cipher alphabet is allowed to consist of any rearrangement of the plain alphabet. The key defines the exact cipher alphabet to be used for a particular encryption.

#10

A secure cipher system must have a wide range of potential keys. For example, if the sender uses the Caesar shift cipher to encrypt a message, then encryption is relatively weak because there are only 25 potential keys. From the enemy’s point of view, if they intercept the message and suspect that the algorithm is the Caesar shift, they only have to check the 25 possibilities.

#11

The substitution cipher was the first method of secret writing to be developed, and it remained the most secure method for centuries. However, codebreakers would eventually find a shortcut to the process of exhaustively searching all keys.

#12

The Abbasid caliphate, which was the ruling dynasty of Islam, was the golden age of Islamic civilization. The richness of Islamic culture was the result of a wealthy and peaceful society. The Abbasid caliphs were less interested in conquest, and instead focused on establishing an organized and affluent society.

#13

The Arabians were able to destroy ciphers, and they in fact invented cryptanalysis, the science of unscrambling a message without knowledge of the key. They were able to do this because Islam demands justice in all spheres of human activity, and the Arabians were able to pursue knowledge in all its forms.

#14

The first great breakthrough in cryptanalysis was made by the ninth-century scientist Abū Yūsūf Ya’qūb ibn Is-hāq ibn as-Sabbāh ibn ‘omrān ibn Ismaīl al-Kindī. He discovered that the letters a and l are the most common in Arabic, and he used this to break ciphers.

#15

It is not possible to apply al-Kindī’s recipe for cryptanalysis unconditionally, because the standard list of frequencies in Table 1 is only an average, and it will not correspond exactly to the frequencies of every text. Longer texts are more likely to follow the standard frequencies, although this is not always the case.

#16

Frequency analysis is the first tool of cryptanalysis. It is used to decipher a ciphertext, and it requires logical thinking, but it also demands guile, intuition, flexibility, and guesswork.

#17

The answer to the encrypted message is OXPP, and the letters are in order according to their frequency in the English language. The most common letters in the ciphertext probably represent the most common letters in the English alphabet, but not necessarily in the right order.

#18

To identify the three most common letters in the ciphertext, O, X, and P, we can focus on how often they appear next to other letters. The letter O typically appears before and after most other letters, but it avoids 15 of them. The letter X is equally sociable, but the letter P is much less friendly. It tends to lurk around just a few letters.

#19

We can start to replace some of the letters in the ciphertext with their plaintext equivalents. I will stick to the convention of keeping ciphertext letters in upper case, while putting plaintext letters in lower case.

#20

We can replace the letters in the ciphertext with their true values. For example, the most common three-letter words in English are the and and, and these are relatively easy to spot. Hence, L probably represents t, P probably represents n, and V probably represents d.

#21

The cryptanalysis of a cipher text is completed when you have established the complete cipher alphabet. The plain and cipher alphabets are the keys that were used to perform the substitution that scrambled the message.

#22

During the medieval period, Arab scholars had a vigorous period of intellectual achievement, while Europe was firmly stuck in the Dark Ages. The only European institutions that encouraged the study of secret writing were the monasteries.

#23

By the fifteenth century, European cryptography was a burgeoning industry. The revival in the arts, sciences, and scholarship during the Renaissance fostered the capacity for cryptography, while political machinations demanded secret communication.

#24

The battle between cryptographers and cryptanalysts was beginning to shift towards cryptanalysts using frequency analysis to break the monoalphabetic substitution cipher, while cryptographers were beginning to use nulls to confuse an attack by frequency analysis.

#25

The term code has a very broad meaning in everyday language, and is often used to describe any method for communicating in secret. However, it has a specific meaning and applies only to a certain form of substitution.

#26

Codes are more secure than ciphers, but they suffer from two major practical failings. First, the sender and receiver must agree on the 26 letters in the cipher alphabet, which limits the flexibility of the code. Second, the consequences of having a codebook captured by the enemy are devastating.

#27

The Battle of Solway Moss in 1542 marked the end of the Scottish army and the beginning of the reign of Queen Mary I. Mary was born prematurely, and there was concern that she would not survive. However, she grew strong and healthy, and was crowned at the age of nine months.

#28

Mary’s first few years in the French court were the most idyllic of her life. She was surrounded by luxury, protected from harm, and she grew to love her future husband, the dauphin. But her husband, who had always suffered from poor health, fell gravely ill. He died in 1560, and Mary was widowed.

#29

Mary, the queen of Scotland, was arrested in 1586 and imprisoned at Chartley Hall in Staffordshire. She had lost all her privileges by 1586, and was treated harshly by her jailer, Sir Amyas Paulet.

#30

The Babington Plot was a plan to free Mary, Queen of Scots, and assassinate Queen Elizabeth. It was planned and executed in 1586, but Mary did not know about it. She received a letter from Gifford, a Catholic priest, who delivered letters from her supporters in France.

#31

Gifford was a youth, and yet he delivered the message with confidence and guile. He was a double agent, secretly working for Mary, but he was also working for Elizabeth.

#32

Walsingham was the most important figure in uncovering the plot against Elizabeth. He was a Machiavellian figure who was in charge of her security, and he had a network of spies that he used to uncover the plot.

#33

The cipher of Mary Queen of Scots demonstrates that a weak encryption can be worse than no encryption at all. Both Mary and Babington wrote explicitly about their intentions because they believed that their communications were secure, whereas if they had been communicating openly, they would have referred to their plan in a more discreet manner.

#34