The Chaocipher Clearing House

Progress Report #9

Moshe Rubin (

Jeff Hill submits research paper entitled "Chaocipher: Analysis and Models"

A few days ago Jeff Hill submitted another, more recent, internal paper of his entitled "Chaocipher: Analysis and Models".  This paper is mandatory reading for anyone interested in Chaocipher research.  In his thorough, clear, and original manner, Jeff gives a clear summary of observed Chaocipher phenomena.  He follows up with an incisive analysis of these phenomena in terms of Markov processes, which leads him to propose several original and thought-provoking hypothetical models that explain the observed traits.

In my opinion, this is the most comprehensive and advanced theory about Chaocipher in the open literature today, and will be of general interest to any cryptanalyst.  I highly recommend fellow researchers to read this excellent paper.

Jeff's paper also contains important historical information.  He provides quotes from letters by William F. Friedman to Byrne which clarify the relationship between them vis-a-vis Chaocipher.  It shows conclusively that Byrne obstinately refused to provide Friedman with a set of messages as per the Army's standard requirements from cipher inventors.  Apparently Byrne had no one to blame but himself for the fact that Chaocipher was not adopted by the US agencies.

Once again, I want to thank Jeff for agreeing to sharing his hard-earned knowledge of Chaocipher with the cryptologic community at large via the Chaocipher Clearing House. 

Copyright (c) 2009 Moshe Rubin
Created: 16 April 2009
Updated: 22 April 2009

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