The Chaocipher Clearing House

Progress Report #24

Moshe Rubin (

Jeff Calof presents Kruh and Deavours's unpublished "Exhibit 6" Chaocipher challenge

In May 2013 Jeff Calof visited the National Cryptologia Museum in Ft. Meade, MD with the express purpose of examining the Chaocipher-related papers donated by Patricia Byrne, wife of John Byrne and daighter-in-law of John F. Byrne.

While perusing this Chaocipher treasure trove he uncovered an unpublished paper prepared by Professor Cipher Deavours and Lou Kruh.  The paper presented a cryptanalytic challenge to students of cryptology, and consisted of fifty (50) in-depth messages enciphered using Chaocipher.  The challenge was meant to correspond to the material William F. Friedman had requested from John F. Byrne in 1942 but had never received.

In this paper, Jeff Calof presents the cryptanalytic community with a truly unique opportunity to "cut its teeth" on a near-real-life challenge to solve the same type of messages that William F. Friedman would have received back in 1942.  More than seventy years later, cryptanalts have a wealth of techniques to use in solving this challenge.

The Chaocipher Clearing House hereby presents Calof's challenge paper, and welcomes comments and solutions from its readers.  Cryptologists and cryptanalysts are invited to submit papers to The Chaocipher Clearing House for publication on this site.

The text of the Kruh and Deavours's fifty challenge messages can be downloaded from this location.

Good luck!

Copyright (c) 2012-2015 Moshe Rubin
Created: 9 January 2015

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