From the earliest days of mankind, people have sought to pass on secret messages via code - and for almost as long, cryptographers have tried to break the codes. Most famous of all were those at Bletchley Park who managed to break the Nazis' 'unbreakable' Enigma code. This fascinating and intriguing book examines some of the most difficult codes in history that have withstood years of investigation and shows the reader how they too can learn to solve or create almost any code. Sometimes, as with the notorious Zodiac Killer or the Voynich Manuscript, the codes remain unsolved, or as with Kryptos in the CIA's headquarters only 90 per cent has been decoded. In the final element of the book, working with a team of top cryptographers, the author has devised his own code, based on the techniques that have been revealed throughout the book, and invites the reader to crack the code...