Create your own encryption programs

Cryptography for Dummies, it could have been the name of this book. Written as a novel, it tells the history of cryptography, describing very simply and very educational very complex encryption algorithms.
Since the letters shift, the use of symbols, to the algorithms used during the war and those used today, this book traces the history and evolution of various encryptions, in the form of a novel.
Following this book, it may very well be able to set ourselves encryption algorithms (obviously, if we as a prerequisite programming basics).
An excellent book if you are curious in this area there.