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+Announcing my Purple simulator
+##############################
+
+:date: 2014-02-20 19:59
+:tags: Python, m209, Enigma, Purple, simulator
+:slug: announcing-my-purple-simulator
+:author: Brian Neal
+:Summary: I recently created a simulation of the Japanese PURPLE cipher machine
+          in Python.
+
+After working on a `M-209 simulator`_ last summer and an `Enigma simulator`_ the
+year before, I got the World War 2 era cipher machine bug again. It all started
+by reading about the `Japanese PURPLE machine`_ at Frode Weierud's excellent
+CryptoCellar_ website. I read with great interest a paper available at that
+site titled *PURPLE Revealed: Simulation and Computer-aided Cryptanalysis of
+Angooki Taipu B* by Wes Freeman, Geof Sullivan, and Frode Weierud. This paper
+is a fascinating read, with detailed descriptions of how the machine worked,
+the complicated keying system employed by the Japanese, and information on
+using a technique known as *hill-climbing* to mount a ciphertext only attack on
+a messages. Highly recommended!
+
+After reading the paper I knew I had to try to write a simulator for the PUPRLE
+machine in Python_. Writing these simulators is great fun. You have to
+understand how the machine works, get a bunch of tiny details correct, have
+a bit of patience, and do a lot of detective work and debugging. Once you have
+them built, they aren't all that complicated when coded on a modern computer.
+But you get an amazing appreciation for these machines as originally
+implemented as electro-mechanical devices. The PURPLE machine, for example,
+required almost 2,000 wired connections! It is even more amazing when you know
+the U.S. code breakers built replicas without even seeing an original Japanese
+machine. When the war ended, only a few parts of one Japanese machine were ever
+recovered!
+
+I had a lot of fun writing this and playing with it. I hope someone else finds
+it interesting or educational. Please contact me and let me know if you use it
+for anything. Please see these links for documentation, the code, and licensing
+details:
+
+* `Purple simulator on PyPI`_
+* `Purple simulator on Bitbucket`_
+
+Once again, many thanks to Frode Weierud, Geoff Sullivan, and Wes Sullivan for
+the very interesting paper. I'm also grateful to Messrs. Weierud and Sullivan
+who provided me with valuable plaintext, advice and encouragement while
+I worked on this project.
+
+I also recommend the book *Battle of Wits: The Complete Story of Codebreaking
+in World War II* by Stephen Budiansky, which details the efforts and the people
+behind the cracking of the PURPLE cipher.
+
+.. _M-209 simulator: https://m209.readthedocs.org/en/latest/
+.. _Enigma simulator: http://py-enigma.readthedocs.org/en/latest/
+.. _Japanese PURPLE machine: http://cryptocellar.web.cern.ch/cryptocellar/simula/purple/
+.. _CryptoCellar: http://cryptocellar.web.cern.ch/cryptocellar/
+.. _Python: http://www.python.org/
+.. _Purple simulator on PyPI: https://pypi.python.org/pypi/purple
+.. _Purple simulator on Bitbucket: https://bitbucket.org/bgneal/purple/