The Code Book
IrishDevThe Code Book starts with Mary Queen of Scots losing her privacy (and a lot more besides) then meanders through the centuries demonstrating how ancients guarded their messages with crude ciphers easily broken but eventually hardened then broken again in a constant battle between those with secrets and those who wish to pry.
There are several detours into how long forgotten scripts were deciphered through comparison with known languages (ancient Hebrew & Greek were the keys to understanding hieroglyphs). The content is somewhat out of date given the current breakneck speed of crypto, but as an introduction to the technology it still serves the content well.
The section about cracking the enigma is fascinating; Poland, having a greater need to break the ultimate encryption machine of the day was driven to succeed...right until the encryption level was increased just prior to the German invasion of Poland. The book progresses through to the RSA, Alice, Bob and public keys, with some consideration of quantum computing. Not bad coverage for a 10-year-old book.
AirSkull