While writing this book I have had the privilege of meeting some of the world’s greatest living codemakers and codebreakers, ranging from those who worked at Bletchley Park to those who are developing the ciphers that will enrich the Information Age. I would like to thank Whitfield Diffie and Martin Hellman, who took the time to describe their work to me while I was in sunny California. Similarly, Clifford Cocks, Malcolm Williamson and Richard Walton were enormously helpful during my visit to cloudy Cheltenham. In particular, I am grateful to Fred Piper of the Information Security Group at Royal Holloway College, London, who allowed me to attend the M.Sc. course on information security.
While I was in Virginia, I was fortunate to be given a guided tour of the Beale treasure trail by Peter Viemeister, an expert on the mystery. I am also grateful to the Oxford Centre for Quantum Computation, Charles Bennett and his research group at IBM’s Thomas J. Watson Laboratories, Leonard Adleman, Ronald Rivest and Jim Gillogly.
Dr Mohammed Mrayati and Dr Ibrahim Kadi have been involved in revealing some of the early breakthroughs in Arab cryptanalysis, and were kind enough to send me relevant documents. The periodical Cryptologia also carried articles about Arabian cryptanalysis, as well as many other cryptographic subjects, and I would like to thank Brian Winkel for sending me back issues of the magazines.
I would encourage readers to visit the National Cryptologic Museum near Washington, D.C., and the Cabinet War Rooms in London, and I hope that you will be as fascinated as I was during my visits. Thank you to the curators and librarians of these museums for helping me with my research.
As well as interviewing experts, I have also depended on numerous books and articles. The list of further reading contains some of my sources, but it is neither a complete bibliography nor a definitive reference list. Instead, it merely includes material that may be of interest to the general reader.
Various libraries, institutions and individuals have provided me with photographs. All the sources are listed in the picture credits, but particular thanks go to Sally McClain, for sending me photographs of the Navajo code talkers; and Brenda Ellis, for allowing me to borrow photos of James Ellis. Thanks also go to Hugh Whitemore, who gave me permission to use a quote from his play Breaking the Code, based on Andrew Hodges’ book Alan Turing – The Enigma.
I have had the enormous good fortune to work with some of the best people in publishing. Patrick Walsh is an agent with a love of science, a concern for his authors and a boundless enthusiasm. John Woodruff has done an excellent job in helping to adapt The Code Book and has contributed greatly to its overall structure. Last, but certainly not least, my editors, Jennifer Wingertzahn and Beverly Horowitz, helped me to adapt the original version of The Code Book into this young readers’ edition. Furthermore, it was Beverly’s idea to undertake this project. For that I am tremendously grateful.