The Code Book covers diverse historical topics including the
Man in the Iron Mask,
Arabic cryptography,
Charles Babbage, the mechanisation of cryptography, the
Enigma machine, and the decryption of
Linear B and other ancient writing systems. Later sections cover the development of
public-key cryptography. Some of this material is based on interviews with participants, including persons who worked in secret at
GCHQ. The book concludes with a discussion of "
Pretty Good Privacy" (PGP),
quantum computing, and
quantum cryptography. The book announced a "cipher challenge" of a series of ten progressively harder ciphers, with a cash prize of £10,000, which has since been won. The book is not footnoted but has a "Further Reading" section at the end, organized by chapter. ==See also==