An Expert System is a program that tries to capture the knowledge of a human
expert in some domain.  CipherExpert is an expert in solving simple
cryptograms, which are encoded messages.  Cryptography is the art of secret
writing, and cryptanalysis is the analysis and decipherment of encrypted
messages.  CipherExpert determines which historical cipher was used based on
a few quick, easy, cryptanalysis techniques, by giving the system the
knowledge that a pre-WWII cryptanalyst would have had.  This program is a
prototype that uses a limited set of historical ciphers, which includes:
Transposition, Caesar, Affine, Vigenere and Playfair ciphers.  CipherExpert
bases its analysis of the cryptograms on the frequency of the letters in the
message.  The two techniques of cryptanalysis that are used include the
distribution of letter frequencies and the index of coincidence, which is a
representation of how flat the distribution of letters is.  
CipherExpert is written in Java and uses the Computer Science Departments
HcryptoJ library, a collection of classes designed for encryption and
decryption. The Java program also communicates with a Jess Expert System,
which is a form of LISP.