I’m getting a bit cheesed off with the Internet: every time I do a search for anything Cipher Mysteries-ish, it seems that half Google’s hits are for ghastly sites listing “Top 10 Unsolved Mysteries” or “10 Most Bizarre Uncracked Codes“. Still, perhaps I should be more grateful to the GooglePlex that I’m not getting “Top 10 Paris Hilton Modesty Tips” and its tawdry ilk.

Realistically, there is only one uncracked code/cipher listing on the web from which all the rest get cut-and-pasted: Elonka’s list of famous unsolved codes and ciphers. But Elonka Dunin has long since moved on (coincidentally, she went from cryptography into computer game production at about the same time that I made the reverse journey), which is perhaps why all of these lists look a bit dated. Perhaps I should do my own list soon (maybe, if I had the time).

Happily, Elonka did manage to nail most of the usual suspects: the Beale Papers, the Voynich Manuscript, Dorabella, Zodiac Killer, d’Agapeyeff, Phaistos Disk, and so on… each typically a piece of ciphertext which we would like to decipher in order to crack a historical mystery. However, one of the items on her list stands out as something of an exception.

For John F. Byrne’s 1918 “Chaocipher”, we have a description of his device (the prototype fitted in a cigar box, and allegedly contained two wheels with scrambled letters), and a fair few examples of both Chaocipher ciphertext and the matching plaintext. So, the mystery isn’t so much a whodunnit as a howdunnit. Though a small number of people are in on the secret mechanism (Lou Kruh, for one), Byrne himself is long dead: and the details of how his box of tricks worked have never been released into the public domain.

Was Byrne’s Chaocipher truly as unbreakable as he believed, or was it no more than the grand delusion of an inspired cryptographic outsider? This, really, is the mystery here – the everything-or-nothing “hero-or-zero” dramatic tension that makes it a good story. Yet hardly anybody knows about it: whereas “Voynich” gets 242,000 hits, “Chaocipher” only merits 546 hits (i.e. 0.0022% as much).

Well, now you know as well: and if you want to know a little more about its cryptography, I’ve added a Chaocipher page here. But the real site to go to is Moshe Rubin’s “The Chaocipher Clearing House“, which is so new that even Google hasn’t yet found it (Moshe emailed me to tell me about it, thanks!) Exemplary, fascinating, splendid – highly recommended. 🙂

OK, enough of the raw factuality, time for the obligatory historical riff. 🙂

I’m struck by the parallels between John Byrne’s device and Leon Battista Alberti’s cipher wheel. Both men seem to have caught the leading edge of a wave and tried to harness its power for cryptography, and made high-falutin’ claims as to their respective cipher systems’ unbreakability: whereas Alberti’s wave was mathematical abstraction, Byrne’s wave was (very probably) algorithmic computing.

Circa 1920, this was very much in the air: when J. Lyons & Co. hired the mathematician J.R.M. Simmons in 1923, the company was thinking about machines, systems, and operational management: mathematical calculators were absolutely de rigeur for them. The first Enigma machines were constructed in the early 1920s (and used in a commercial environment), and there were doubtless many other broadly similar machines being invented at the same time.

Do I think that there was anything unbreakable in Byrne’s box? No, not really: the real magic in there was most likely a programmatic mindset that was cutting-edge in 1918, but might well look somewhat simplistic nearly a century later. But I could be wrong! 😉

8 thoughts on “All about the Chaocipher…

  1. cybermacht on May 10, 2009 at 6:52 am said:

    im a logarythm expert
    i have 3 of the giants down

  2. Hi cybermacht,

    Sorry, I don’t know what you mean by “3 of the giants”… can you explain, please?

    Cheers, ….Nick Pelling….

  3. yeah, take a look at my page. i consider “giants” the rest of the uncracked codes on chriptology


  4. Hi cybermacht,

    I look forward to seeing your solutions to the Dorabella Cipher etc. Please let me know when they go live on your site!

    Cheers, …Nick Pelling…

  5. Hi Nick,

    A lot of water has flown under the Chaocipher Clearing House (TCCH) bridge since your initial posting. I just wanted to point you and your readers to the fact that TCCH now hosts the most comprehensive collection of letters between John F. Byrne (the inventor of the Chaocipher) and William F. Friedman (the father of American cryptology). You can check it out at on the TCCH site.

    I believe your readers will find the letters provide the important historical perspective that has been missing until now.



  6. of course nick. Dorabella is done as well, ill show the solution very soon.

    Now im focused on a more graphical explanation to the D’Agapeyeff Cipher so everyone can understand what im saying. Its all about binary alphabet. Thanks

  7. Hi Nick,

    Apologies for posting on an old page. This is new material for some…

    If one takes the first 104 lines of the coding in Chpt. 21 of “Silent Years” into account:

    For the first letter of each line, the AVERAGE number of times each letter of the alphabet was used is about (exactly) 4 times.

    If the character sampling to represent each letter was done at random (or randomly picked from all possible letters, as spoken about in “Silent Years.”) the total number of lines used in the sample (104) divided by the average number of times each letter was used (4) should show the approximate number of variable characters which would be used to represent each letter.

    So, the probable number of characters used to represent the “A” in the first line of each of the 104 lines is: 104/4 = 26.

    This formula can be applied to the second and third letter for each line. The 2nd character set gives 26.25, and the third 26, exactly again.

    This small statistical sampling suggests that there was a wheel of about 26 characters, which could easily be the letters A to Z.

    So how was a cypher made?

    The original message was written down. For each letter in the message, the wheel was spun and the new letter was written down next to the letter to which it corresponded. In this manner, the message was transcribed into a cypher. Only the holder of the the original message would know the meaning of the cypher.

    Of course, this would pose a problem. The original message, and the cypher, would need to be shown to the intended recipient. So, although the language of the message was obliterated, the transmission of the original message was still unencrypted. Ouch.

    This would elicit a polite refusal from most government entities, and a suggestion for its use as a toy by any savvy lawyer.

    This so anticlimatic that it is difficult to propose.

    Special Sauce

  8. Mike Cowan on January 31, 2011 at 3:03 pm said:


    You have written off Chaocipher as breakable despite the fact that nobody broke it for some 60 years — and there are still elements (Exhibits 2 and 3) where the original keys cannot (to date) be found. Would you like to give us your ideas on how a ciphertext-only attack on Chaocipher would succeed?

    BTW I have solved the keys for Exhibit 1 (as have a number of others) and for Exhibit 4, together with the hitherto undeciphered sections of Exhibit 4 (see my paper at Chaocipher Clearing House which, as far as I know, is the only published solution at this time.)

Leave a Reply

Your email address will not be published. Required fields are marked *

Post navigation