The Code Book by Simon Singh

The Code Book is one of the finest popular science books ever written about cryptography and the history of secret communication. Simon Singh traces the 4,000-year history of code making and code breaking, from the simple substitution ciphers used by Julius Caesar to the unbreakable quantum cryptography systems of the twenty-first century.

Singh tells the story of cryptography through a series of dramatic historical episodes. He covers Mary Queen of Scots’ fatal reliance on an enciphered correspondence with her co-conspirators, the Vigenère cipher that was considered unbreakable for 300 years until Charles Babbage cracked it, and the extraordinary story of the Enigma machine used by Nazi Germany and the British codebreakers at Bletchley Park who broke it, arguably shortening World War II by two years.

The second half of the book covers modern cryptography, including the revolutionary concept of public-key encryption that makes online commerce and secure communication possible. Singh explains the mathematics behind RSA encryption in terms that any patient reader can follow, and he explores the ongoing battle between governments that want the ability to conduct surveillance and citizens who want genuine privacy.

The book concludes with a look at quantum cryptography — a system based on the laws of quantum mechanics that is theoretically unbreakable — and considers what the future of secure communication might look like as computing power continues to grow. Singh writes with a novelist’s sense of drama and a scientist’s precision, making The Code Book a genuinely thrilling reading experience.