The Chaocipher Clearing House

Progress Report #22

Moshe Rubin (

Upcoming in January 2014 Cryptologia: Kruh and Deavours's 1990 Chaocipher challenge solved

Paper written by Jeff Calof et al describes the history, analysis, and solution

Chaocipher researchers have puzzled over Cipher Deavours and Lou Kruh's challenge messages in the July 1990 issue of Cryptologia.  Now, at long last, a paper authored by Jeff Calof (with co-authors Jeff Hill and Moshe Rubin) entitled "Chaocipher Exhibit 5: History, Analysis, and Solution of Cryptologia's 1990 Challenge" is scheduled for publication in the January 2014 issue of Cryptologia.  Here is the article's abstract:

"Chaocipher is a method of encryption invented by John F. Byrne in 1918 who, over the next 40 years, unsuccessfully tried to interest various U.S. Government Agencies and Private Industries in his cipher system. His 1953 biography included a series of challenge ciphers he labeled Exhibits 1 – 4. In 1990, John Byrne (son of John F. Byrne) revealed and demonstrated the Chaocipher algorithm to Professor Cipher Deavours and Louis Kruh. Without revealing the encipherment process, they in turn published an article including a new series of challenge ciphers they called Exhibit 5. Twenty-three years later, and three years after the first public revelation of the Chaocipher algorithm, Exhibit 5 remained unsolved. Following a 2013 visit to the National Cryptologic Museum (NCM) in Ft. Meade, Maryland to research the recently donated Byrne family materials on the Chaocipher, co-author Jeff Calof found two documents prepared by Deavours & Kruh pertaining to Exhibit 5. One document provides their encipherment schema and solution for the published version, while the other is for an earlier draft whose challenge ciphers differ markedly from that of the published article.

This paper presents a review of Exhibit 5’s creation, an analysis of the restrictions placed on Deavours and Kruh when writing their article, their enciphering schema and source material for the published Exhibit 5, irregularities with the published ciphertext, and an overview and comparison with their unpublished Exhibit 5 draft and challenge ciphers."

John F. Byrne's Exhibits 2 and 3 in "Silent Years" are finally solved!

Finnish math student Esa Peuha discovers the method used to encipher Exhibits 2 and 3

To date, Chaocipher Exhibits 1 and 4 found in John F. Byrne's autobiographical "Silent Years" have been deciphered, analyzed, and written about.  It has been found that they both use the classic Chaocipher algorithm

On the other hand, Exhibits 2 and 3 have eluded Chaocipher researchers to date.  The NSA web site has provided links to John F. Byrne's Exhibit 2 notes, but researchers were not able to prove that the exhibit followed the same classical Chaocipher method used in exhibits 1 and 4.  Up until now no one has been able to explain how they were enciphered.

On 18 September 2013 I received the following email from Esa Peuha, a Finnish math student:

"I have figured out how Byrne encrypted Exhibits 2 and 3. The attached file has the details, but the short version is that only the first 52 letters of Exhibit 2 are actual Chaocipher, the rest of it and all of Exhibit 3 use a simpler method that switches alphabets after every 52 letters. Since your article in Cryptologia mentions a document from the National Cryptologic Museum related to Exhibit 3, I was wondering if you have scans of it (and any other possibly relevant material) that you would be willing to share?"

Esa attached a two-page PDF document briefly describing how Chaocipher Exhibits #2 and #3 were enciphered.  It did not take me long to verify that Esa had indeed cracked the encipherment of both Exhibits 2 and 3.  Esa's initial paper showed how Byrne enciphered the exhibits, making use of Byrne's work sheets found on the NSA web site, but some more work was required to determine the keywords used to generate successive alphabets.  This information was ultimately provided by material photographed by Jeff Calof during his recent trip to the National Cryptologic Museum.

Be sure to read Esa Peuha's analysis of Exhibits 2 and 3.  Here are links pointing to some of the references in Esa's paper:

Exhibit 2 Working Draft A
Exhibit 2 Working Draft B
Exhibit 3 Encipherment Grids

Copyright (c) 2012-2013 Moshe Rubin
Created: 4 October 2013

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