The book opens strongly at the trial of Mary Queen of Scots, where her life is forfeit should her enciphered correspondence be read. This provides an opening for Singh to relate a history of the techniques used in attempts to make correspondence secret, and to read the secrets: since ancient times men - mostly men, mostly in pursuit of war - have used the latest techniques both to make and break ciphers and codes.
During the course of the book Singh relates the story of new cipher techniques and how in turn each method was cracked, in an arms race which - as he relates it - is almost over. Digressions include the Rosetta stone, Egypian hieroglyphics and the decipherment of Linear A - all fascinating stuff. Finally, by the middle of the twentieth century formidable technologies made secret messages almost impenetrable - technologies including, of course, Enigma.
The book deals with Enigma at length, and shows how it was broken by a combination of insight, genius and German fallibility. Had the Germans used it properly, it probably would not have yielded to Bletchley Park's efforts.
Rather frustratingly at this point, Singh mentions the American and British wartime cipher machines but gives no further details - and this raises the question of secrecy, because the more contemporary his account becomes the less information is available. The vast majority of work in these areas is carried out by governments, and they are understandably wary of sharing their discoveries.
As an example, the unbreakable-by-any-publicly-known-means technology of RSA encryption, available freely to many millions of computer users the world over, was discovered three years earlier by researchers at GCHQ.
Finally, Singh deals with quantum computers - if buildable, they might
easily crack all current encryption systems - but they will also offer
the potential of a new, never crackable system. The arms race would be
over, and for the first time secure messages would remain secure, for
ever.
Seán 27/8/00