The Code Book Book Summary - The Code Book Book explained in key points
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The Code Book summary

Simon Singh

The Science of Secrecy From Ancient Egypt to Quantum Cryptography

4.2 (38 ratings)
21 mins

What is The Code Book about?

The Code Book (1999) lays out the long and intriguing history of secret communication. These blinks will take you on a journey from Ancient Greece to the modern-day NSA, detailing innumerable stories of cunning, determination and deceit along the way.

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    The Code Book
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    Secret codes developed early on in human history and evolved quickly.

    While secret codes might seem like a relatively modern phenomenon, the earliest known form of cryptography, that is, the practice of concealing the meaning of a message, actually dates back to the fifth century BC! It was at this time that Greece, faced with the constant threat of being conquered by Persia, realized that secure communication was essential.

    The result was cryptography, a field that simultaneously developed two distinct branches: transposition and substitution.

    Transposition works by rearranging the letters of a word or sentence to produce a cipher, a secret method of writing. For instance, the rail fence cipher, a popular form of transposition, alternates the letters of a message in a zigzag pattern that moves between two consecutive rows.

    The other method, substitution, is a system wherein one letter stands for another. For instance, A=V, B=X and so on until every letter of the alphabet has a substitute pair, thereby forming a cipher alphabet. Since this process forms an alphabet that replaces the conventional one, it is referred to as a monoalphabetic cipher.

    For example, one of the simplest forms of substitution is called the Caesar shift cipher, so named because it was favored by Julius Caesar himself. It works by using the standard alphabet but shifting the letter it begins on by a set number of characters. So, if you shifted the alphabet three places then A=D, B=E, C=F and so on.

    However, simple Caesar shift ciphers only fooled dedicated adversaries for so long and eventually the keyword cipher alphabet was formed, adding a twist to the monoalphabetic cipher. This cipher is similar to the Caesar shift except the alphabet starts with a keyword or phrase, at which point the conventional alphabet resumes but without the letters used in the keyword.

    For instance, if “Caesar” was the keyword, the alphabet would begin CAESRBDFGHIJK… Therefore A=C, B=A, C=E, D=S, and so on.

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    Best quote from The Code Book

    At the end of the 19th century, cryptography was in disarray.

    —Simon Singh
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    About the Author

    Simon Singh holds a PhD in physics from Cambridge University. He wrote the bestselling book Fermat’s Enigma and directed the award-winning documentary, Fermat’s Last Theorem.

    Who should read The Code Book?

    • Anyone interested in codes, secrets and world history
    • People with a taste for stories of wartime espionage
    • Any linguist and mathematician

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