Decrypto 8
(C) 2006 by Edwin Olson
eolson@mit.edu

INTRODUCTION

Decrypto 8 is a simple substitution cipher solver, capable of solving
most "cryptoquips" or "cryptograms" found in papers and
elsewhere. Decrypto uses a dictionary attack, meaning it uses a list
of english words as guidance in solving.

WHAT'S NEW?

The focus for version 8 was improving Decrypto's performance on
difficult puzzles. Difficult puzzles contain non-dictionary words, or
are generally underconstrained. These puzzles would either run for
exceptionally long periods on earlier versions, or would terminate
immediately with zero solutions.

Version 8 combats these two problems in two ways:

	1. It has the ability to evaluate the probability of
correctness of each solution that is found. It uses a table of digram
probabilities to do this. This allows us to report only "good" partial
solutions; displaying partial solutions in previous versions would
have produced megabytes of output. 

	2. The underlying search algorithm has been updated to reduce
the set of candidate words at each search tree node. This greatly
reduces the depth of the final search tree, allowing version 8 to
explore more solutions in less time.

Version 8 is also written in pure Java, allowing it to be run on any
platform. 

Finally, Version 8's innards have been reworked to allow -- in theory
-- Decrypto to be used on puzzles in different languages. Previously,
foreign languages were "supported" by mapping each foreign letter onto
an English letter A-Z. Now, foreign alphabets with up to 63 letters
are supported. There are no dictionaries yet, however; contributions
are welecomed!

HOW TO RUN

From Windows:

	Double click on the JAR file. If that doesn't work, you
probably need to install the Java Runtime Environment (JRE), available
from http://java.sun.com.

From Linux/MacOS X:

	From the shell, type:

	java -jar decrypto.jar


CONTRIBUTIONS

Creating Decrypto, and updating it through 8 significant revisions,
takes a great deal of time. If you'd like to make a donation (perhaps
enough for a pizza and coke), send it to:

Edwin Olson
61 Harvey St.
Cambridge, MA 02140

And my sincere thanks to the handful of users which have sent me
contributions in the past!
