In 1999, Simon Singh published The Code Book. The book invites its readers to take part in a competition known as the Cipher Challenge. This competition has attracted a large and international audience. A mailing list has for instance been set up as a forum for discussions on the competition.
This document gives a description of how we proceeded to solve the problems posed in The Cipher Challenge. The document gives both a popular description and overview information, as well as more in-depth descriptions of the hunts for solutions for the specific stages. We have tried to organize the document in such a way that it can be read by anyone. Some chapters do assume computer or cryptographic knowledge. When this is the case, the technical description of how each stage was solved is usually in a separate section. The reader who so wishes can skip these sections and still be able to understand the rest of the document.
We warn any reader who still wants to complete the challenge that this document is a major spoiler for all stages. So for a reader who does not want to see any spoilers, it is not a good idea to read this report.