"The Code Book" by Simon Singh

The book starts by explaining steganography and cryptography. Steganography is the process of hiding a message, while cryptography is the process of hiding its meaning. Examples of both are given with information on how the codes are used, and how they were broken. The main example is Mary Queen of Scot's code, the weakness of which led to her execution.
Later, the book moves onto stronger forms of encryption such as the Vigenere square and homophonic substitution ciphers, which became popular after the 16th century. Continuing chronologically the chapter examines popular codes up to a…