For almost as long as there have been civilisations to spy on each other, there have been people doing so. And a great asset to any spy is a means of concealing the contents of their messages. This gave rise first to the art of hiding the messages themselves, and then, more practically, hiding the meaning: cryptography. For a long time simple substitution (replacing one letter with another) was all that was needed. But as the codebreakers began to gain the upper hand more sophisticated systems were required, from complex substitutions to code machines like the famous Enigma to the more recent field of computer encryption. This book tours the whole history of code-making and -breaking, from the earliest means of hiding messages to as much as can be known of the present and beyond.
By the very nature of its subject, this is not a complete history; after all, modern spy organisations are hardly likely to reveal their current - or even recent - encryption or decryption methods. Which probably explains the inclusion of chapters on computer encryption as a way of bringing the history up to the present; not something I would have thought of in connection to codes, but perfectly logical once someone else mentions it (and written in such a way that even I could understand the principles). Another detour into something other than traditional codebreaking was a section on the decipherment of ancient languages, such as hieroglyphics or the Minoan Linear B. Just as fascinating as the history was that the work was largely done by amateurs (albeit very linguistically talented and knowledgeable ones).
As interesting as the history was, my favourite thing about the book was the number of opportunities it gave readers to test their own brainpower. A good number of codes are described in enough detail to make them usable - and breakable. The chapter on Enigma included something I’d been curious about for ages: a clearly readable image of the crossword used by the Times to recruit codebreakers. (I drew up a duplicate grid and had a go myself - and discovered that I wouldn’t have been allowed anywhere near Bletchley Park.) The book also reproduces the famous Beale ciphers, which supposedly detail a cache of buried treasure. Two have been solved, but the most important one, explaining how to actually find the treasure – hasn’t (not that that deters people from turning up with shovels anyway). An appendix helpfully lists those ancient scripts yet unsolved; a tempting prospect, but given that beyond the confines of English I am linguistically talentless I don’t think I’ll be the one to make the breakthrough on Etruscan or Linear A. And at the back of the book is a ten-step Cipher Challenge; prize money long since claimed, but hugely entertaining none the less ... even if I am still stuck on Step 3.