The Kamasutra encourages women to study 64 arts. These include massage, the preparation of perfumes, dressing, conjuring, chess and bookbinding. Number 45 on the list is melecchitavikalpa, the art of secret writing, which can be used as an aid to concealing liaisons. One of the recommended techniques is to pair letters of the alphabet at random, and then substitute each letter in the original message with its partner. The Kama-sutra was written in the fourth century AD, making this one of the earliest descriptions of encryption by substitution.
Simon Singh's discourse on code-making and breaking is a fascinating meander through the centuries, replete with tales of intrigue, political chicanery, military secrecy and academic rivalry, wending its way to the future: the dizzying world of quantum physics.
The earliest description of serious codebreaking is contained in a manuscript written by the 9th century "philosopher of the Arabs", al-kindi. The development of frequency analysis, first in the Arab world, and then in Europe, meant simple substitution ciphers were no longer safe.
On February 18th, 1578, an audience of 300 gathered to witness the beheading of Mary, Queen of Scots. She was put to death as a result of her involvement in the Babington Plot, which was to free her, kill her cousin Queen Elizabeth and incite a rebellion. Her sanction of the plot was conveyed by cipher but it was broken by Thomas Phelippes, one of Europe's finest cryptoanalysts.
Ironically, this was the same year that Blaise de Vigenere, a French diplomat, developed the Vigenere cipher, which was to remain unbroken until the 1850s, when it was finally cracked by Charles Babbage. If only Mary's secretary had read Vigenere's treatise, Traicte des Chiffres, May's messages to Babington would have baffled Phelippes and her life might have been spared.
Code-breaking played a large part in strategy in both World Wars. The fight to crack the secrets of the German Enigma machine are well documented. Code-breaking requires a variety of skills. When Winston Churchill visited Bletchley Park, the headquarters of the British codebreakers, in 1941, he was surprised by the "bizarre mixture of people providing him with such valuable information" - in addition to mathematicians and linguists, there was an authority on porcelain, a curator from the Prague museum, the British chess champion and numerous bridge experts.
The book ends with a discussion of modern-day cryptography, including RSA, the cipher used to encrypt computer files so they can be emailed securely.
The Code Book is a good read, if not better than Singh's best-selling Fermat's Last Theorem. Singh's strength lies in his ability to explain complex topics clearly. However, both books would have benefited from some culling of the more detailed mathematics, which could have been relegated to the appendix.
Quibbles aside, anyone interested in cryptography, science, maths or history will love this book. It comes complete with a cipher challenge. A prize of £10,000 will be awarded to the first person to crack all its 10 elements.
Anne Byrne is an Irish Times journalist