What is Chaocipher?

Moshe Rubin (mosher@mountainvistasoft.com)

"Chaocipher" is the name John F. Byrne (11 February 1880 - April 1960) gave to a cipher system he invented in 1918.  Byrne, born in Ireland, was a close friend of the famed author James Joyce, and was an unlikely candidate for devising a strong cryptosystem.  From the time of his invention until his death he indefatiguably tried to interest goverments and organizations to use his system.

Unfortunately, his system failed to be taken seriously by those he approached.  This was due, in a large part, to Byrne's steadfast refusal to provide William F. Friedman with the standard number and type of challenge messages requested from every cipher inventor that approached the US military organizations.

In 1953 Byrne published his autobiographical "Silent Years".  The book contained much about his memories of James Joyce, but the reason for writing the book was to publicize Chaocipher to the world.  The 21st chapter in "Silent Years" contains loads of plaintext and corresponding ciphertext, more than would normally be expected.  In addition, there are a few enciphered lines whose plaintext is not provided.  Byrne challenged the world-at-large to decipher these few lines.

Chaocipher has not been 'cracked' to date and remains one of the premier unsolved cipher challenges today.  (Update: The Chaocipher principle was publicly released in June 2010.)

Here is a quotation about Chaocipher from David Kahn's monumental book "The Codebreakers" (1969), pages 767-768:

Classic in the annals of cryptographic invention is the case history of John F. Byrne, who stuck with his cipher through repeated rebuffs for more than 35 years.  Byrne was an intimate of James Joyce: they were students together at Dublin, and Joyce modeled Cranly in his Portrait of the Artist as a Young Man upon Byrne, and made Byrne’s residence, 7 Eccles Street, Dublin, the home of Leopold and Mollie Bloom, the two protagonists of his great Ulysses.  It was in 1918 that Byrne hit upon the principle of his "Chaocipher", which he never disclosed publicly but was an autokey.  It required nothing more than a cigar box and a few bits of string and odds and ends for its operation.  When he showed it to his cousin, she exclaimed that it would bring him a Nobel Prize -- not for science, apparently, but for ushering in an age of universal peace by conferring the gift of perfect security upon the communications of all nations and all men. Wrote Byrne:

"When I first set out to discover a system for concocting an indecipherable cipher, I had it clearly in mind that such a system would and should be universally available.  I envisioned, for instance, the utilization of my method and machine by businessmen for business communications, and by brotherhoods and social and religious institutions.  I believe that my method and machine would be an invaluable asset to big religious institutions, as for example the Catholic Church with worldwide ramifications.  I had, and still have in mind the universal use of my machine and method by husband, wife, or lover.  My machine would be on hire, as typewriter machines now are, in hotels, steamships and, maybe even on trains and airliners, available for anyone anywhere and at any time.  And I believe, too, that the time will come -- and come soon -- when my system will be used in the publication of pamphlets and books written in cipher which will be unreadable except by those who are specially initiated."

Byrne corresponded with Colonel Parker Hitt, and in 1922 demonstrated his machine before [William F.] Friedman and Colonel Frank Moorman, former head of G.2 A.6, then handling cryptography for the Signal Corps.  They did not want it.  He offered it to the State Department, which replied with a form letter stating that its "ciphers are adequate to its needs" -- a statement that Byrne rightly damned as "a paragon of smugness."  He submitted it to the Navy in 1937-39, negotiating apparently with Commander Joseph N. Wenger, and to A. T. & T.’s Ralzemond D. Parker, chief of company development and research and Vernam’s boss when he invented the on-line mechanism.  Nobody took it.

Byrne’s faith remained undaunted.  He had a little brochure printed in which he enciphered known texts in his Chaocipher and defied the world to break it.  Toward the close of his life, he wrote a book of reminiscences.  It told much about his days with Joyce, but his real reason for writing it was not to shed light on early Joyce but to get his Chaocipher before a larger audiences.  The 21st and last chapter of Silent Years: An Autobiography with Memoirs of James Joyce and Our Ireland, comprising fully one eighth of the book, recapitulated the story of his Chaocipher.  Byrne concluded by betting $5,000 or the total royalties of the first three months after publication of his book that no one would be able to solve the message in Chaocipher that he printed in extenso in the final pages. He flung the challenge also at the amateurs of the American Cryptogram Association and the New York Cipher Society and at Norbert Wiener, father of cybernetics, and to other believers in the capabilities of the electronic calculating machines.

Nobody ever claimed the money, and Byrne died a few years later. One may presume that the reason both for the failure of the public to read his cipher and for the failure of the government to adopt it was that while the cipher probably had many merits, its many demerits outweighed them for practical use.  Byrne, like many inventors, both won and lost.  His cipher was never broken.  But his dream never came true.

Copyright (c) 2009 Moshe Rubin
Created: 2 September 2009
Last updated: 18 January 2013

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