This looks like it could have been inspired by the Cipher Challenge[1] from The Code Book[2], which starts with monoalphabetic substitution problems. 1. http:/

This looks like it could have been inspired by the Cipher Challenge[1] from The Code Book[2], which starts with monoalphabetic substitution problems. 1. http://simonsingh.net/cryptography/cipher-challenge/the-ciphertexts/ http://simonsingh.net/cryptography/cipher-challenge/the-ciph... 2. http://www.amazon.com/The-Code-Book-Science-Cryptography/dp/0385495323 http://www.amazon.com/The-Code-Book-Science-Cryptography/dp/...