The Cipher Challenge
- History of a code cracking competition. Challenge details, how it was solved, winners, essays and photo gallery.
- http://www.simonsingh.net/Cipher_Challenge.html

Plus Magazine - Singh's "Code Book" Challenge Cracked
- "The £10,000 prize Singh offered for the winner of this "cipher challenge" has now been won by a team of five Swedish researchers." Article explains the challenge, how it was constructed, and what it took to solve it.
- http://pass.maths.org.uk/issue13/news/codes/

Code Book Cipher Challenge Solution Page
- Gives solution to Singh's Cipher Challenge. Includes the list of authors, the order of solutions, and the steps to create a team. In HTML, PDF and postscript format.
- http://codebook.org/