The Chaocipher Clearing House

Progress Report #29

19 April 2026

Moshe Rubin (mosher@mountainvistasoft.com)

This Progress Report summarizes developments in Chaocipher research, publications, and historical discoveries since Progress Report #28 (January 2023).

Here's a table of contents for this report:

Chaocipher and Cryptology

Byrne Genealogical Information



Chaocipher and Cryptology

A Chaocipher Challenge Message on Reddit

In July 2020, Reddit poster YaF3li presented several cipher challenge messages.  Challenge message #4 is a Chaocipher-encrypted message.  Originally, only the ciphertext was provided. The author soon expressed doubts about the fairness of the challenge ("It is Chaocipher, but the length of the ciphertext might be too short to solve, I'm not sure. If so, let me know. I just found the thing fascinating, that's why I included it.").  To address this, he later added the plaintext.

Here is a good challenge for Chaocipher analysts: given the ciphertext and corresponding plaintext, can you deduce the left and right alphabets used to encipher the plaintext?

Ciphertext:
    RWTJQ CBRAN SDDIJ IWPMT XTSSM BPQWW QLHTG ATWNL CZCHH WXSYS KEYZV ZITCA HZPZE QNBXT YQCBB VOBBI
    WTTWE GVCVE RLVUH XJXHT BEMPZ VONCX JPQRN BXTIK GBPQQ ZHPWX XELXA LFPXY KZYDS FAWNP WEOHO EPDVQ
    FFOGE RHZSP XRJLK BIKIU APPRN ILKSQ OTQPM GCAKK JJ (202 characters)

Plaintext:
    OKAY SO THIS IS JUST A TEST BASICALLY BECAUSE I HAVE NO IDEA WHETHER THIS IS SOLVABLE GIVEN THE
    RELATIVELY LITTLE AMOUNT OF CIPHERTEXT HERE AGAIN THE REST HERE IS PADDING SO IT IS AT LEAST A
    LITTLE LONGER IN THE HOPE THAT THIS HELPS WITH DECRYPTION (202 characters)

William F. Friedman mentions Byrne to Henry Langen in a letter

Henry E. Langen was the Editor of the American Cryptogram Association between the years 1952-1956.  Although a cryptographic amateur, he brought energy to his position and wrote many columns in The Cryptogram to spur interest in the hobby.

Langen is connected to Chaocipher due to John F. Byrne's paying him a visit in May 1954, during which they discussed Chaocipher.  Byrne misled Langen by claiming he had a working demonstration model, apologizing that it was too heavy to bring. In reality, no such functional model existed; only a wooden prototype with movable tiles.

On the NSA site one can read a letter from William F. Friedman to Langen, dated June 1954.  In the letter, Friedman acknowledges whatever Langen wrote him about Byrne.  Friedman was not interested in Chaocipher, and only replied "Your mention of Mr. Byrne reminds me that I gave a brief review of his book before a local group devoted to the study of James Joyce.  I had a very interesting time and I hope my audience did, too."

Publications that mention Chaocipher

Academic publications are citing the Chaocipher with increasing frequency. Researchers are analyzing its structure, comparing it with other encryption methods, and incorporating it into diverse areas of study. The cipher is gradually moving from historical curiosity to a recognized topic in contemporary cryptologic research.  Following are several such publications

Publication: Steganography and Cryptography Inspired Enhancement of Introductory Programming Courses

A paper titled "Steganography and Cryptography Inspired Enhancement of Introductory Programming Courses" (Yana Kortsarts and Yulia Kempner) was published in the July 2015 issue of Information Systems Education Journal.  As their abstract says:

Steganography is the art and science of concealing communication. The goal of steganography is to hide the very existence of information exchange by embedding messages into unsuspicious digital media covers. Cryptography, or secret writing, is the study of the methods of encryption, decryption and their use in communications protocols. Steganography manipulates data to ensure the security of information, but the concept of steganography differs from cryptography. Cryptography obscures the meaning of a message, but it does not conceal the fact that there is a message. The goal of cryptography is to make data unreadable by a third party, whereas the goal of steganography is to hide the data from a third party. We present a way to integrate steganography and cryptology examples into introductory programming courses. This enrichment promotes active involvement in the course and provides opportunity to engage students in experimental problem solving and collaborative learning to enhance critical thinking.

On page 28, the authors bring Chaocipher as an example of a dynamic substitution cipher:

Dynamic substitution cipher - Chaocipher

Recently, we also integrated into the course curriculum, a less known and more complex cipher, chaocipher, (Byrne, 1918; Rubin, 2010), belonging to the group of dynamic substitution ciphers. [. . .] In our approach we closely follow the description of the algorithm published in July 2010 by Moshe Rubin (2010), providing further adaptation and clarifications for novice programmers. [. . .] To ease the transition and increase the difficulty level gradually, we first permit students to use additional array/list storage, increasing the space complexity of the algorithm. As a complete implementation, students are required to implement all these array/list manipulations with minimal additional space usage. To avoid any attempts at plagiarism, we provide only cipher description and all necessary details to design a computational implementation. We emphasize the mystery around this cipher to keep students motivated and excited. We reveal the name and history of the cipher only after students complete writing the program, but before the collaborative testing step of the assignment. The mystery around this cipher and the interesting history attract students’ attention. This cipher provides an opportunity to practice complex manipulations of one- dimensional arrays and lists data structures, utilizing a wide range of built-in Python lists methods and functions, and writing custom functions in C. From the best of our knowledge, this cipher is not covered in any cryptography textbooks.

Publication: Digital Signature on Digital Images using the Least Significant Bit Algorithm and the Chaocipher (Indonesian)

The paper "Digital Signature on Digital Images using the Least Significant Bit Algorithm and the Chaocipher" (Siwabessy, 2016) is a Bachelor of  Computer Science submission written in Indonesian.  Translated from the abstract:

Documents in the form of digital image has the possibility to be manipulated unlawfully. The information contained within can be faked, so that the recipient of the document can be wrong in interpreting the intention of the information therein. This could result in losses for both the sender and recipient document, the decision made, based on the information that has been falsified. A solution is needed to secure the information stored on it. Information from the sender must be the same when it reached the receiver. In this study generated digital signature applications implemented in a way that is calculating the value of bytes of data into a form MD5 hash algorithm. Results hash is then encrypted with an algorithm Chaocipher. Cipher hash then inserted at Least Significant Bit of digital images. Digital signature is inserted can be used to detect whether the digital image has been changed or not. The test results showed that the change can be detected, even if the change only by 2x2 pixels.

It is encouraging to see Chaocipher gaining traction in academic research, not only as a historical artifact but as a system that continues to inspire analysis and experimentation.

Publication: Analyzing and Creating Playing Card Cryptosystems

Isaac Reiter is the author of the 2020 paper "Analyzing and Creating Playing Card Cryptosystems", submitted in as an honors mathematical paper at the Kutztown University of Pennsylvania.  In this paper, Reiter proposes a new card-based cryptosystem.  This proposed system incorporates features from the Card-Chameleon  and Chaocipher playing card cipher systems and improves on them.

From the abstract:

Dr. Landquist and I spent the summer of 2019 examining existing playing card ciphers. This led to the main focus of this paper: the creation of a unique, secure playing card cipher. Because of the inspiration provided by the cipher VIC, I am calling our original cipher VICCard. VICCard has gone through multiple versions, each better than the last. Its security is rooted in its combination of numerous cryptographic principles, including a substitution checkerboard, columnar transpositions, lagged Fibonacci generators, and junk letters. As evidenced by certain randomness tests, VICCard has the potential to extensively randomize an English plaintext.

Regarding Chaocipher, Reiter writes (page 8):

Second, Chaocipher is a cryptosystem that was created by John F. Byrne in 1918. Although Chaocipher has been around for over a century, the disclosure of the Chaocipher algorithm occurred as recently as 2010. As he was examining previously invented playing card ciphers, Toponce had the idea of adapting the Chaocipher algorithm to playing cards. Given the respectable security of Chaocipher, I did not find a weakness that was as severe as that in Card-Chameleon. The closest thing to a weakness is the existence of plaintext/ciphertext pairs (or pt/ct pairs). A pt/ct pair is when two identical plaintext letters encrypt to the same ciphertext characters, such as two a’s encrypting to two o’s. Greg Mellen noticed that when he divided messages encrypted by Chaocipher into blocks of 13 letters, pt/ct pairs rarely occurred within these blocks. Moshe Rubin hypothesized that pt/ct pairs will only occur if the two plaintext letters are separated by a distance of eight letters. In order to put a rest to this question, I wrote a program that took two a’s and tried every 1-letter, 2-letter, 3-letter, 4-letter, and 5-letter combination between these two a’s. After testing all 12,356,630 of these cases, the program did not find any pt/ct pairs. However, it did find pt/ct pairs with certain 6-letter combinations. As a result, we can say for certain that at least six letters must be between two plaintext characters for a pt/ct pair to occur.

Two clarifications should be made here:
  1. The paragraph contains an inaccuracy: the text should read "Moshe Rubin hypothesized that pt/ct pairs will only occur if the two plaintext letters are separated by at least a distance of eight letters."  This appears to be what the author intended.
  2. Reiter is to be credited with empirically showing that the minimal number of intervening letters between identical pt/ct pairs is six (6), as he explains in the paragraph.  At the same time (also in 2020), Moshe Rubin proved this identical result mathematically.

Publication: Code Complexity Overview, and an Analysis for Various Programming Languages

The paper, Code Complexity Overview, and an Analysis for Various Programming Languages, by Cameron Reid (2024), evaluates the algorithmic complexity of a wide range of programming tasks using a custom metric. Chaocipher receives a score of 6.351905, placing it among moderately complex tasks such as matrix‑chain multiplication and bounded knapsack.

From the abstract:

Software complexity is notoriously difficult to measure, but can have a profound impact on the performance of a software development team and the continuing robustness of a software product. Significant effort has been made for many years to attempt to measure software complexity, as this is a problem that can have significant financial impact. Software that is too complex may also be too difficult to modify, understand, or debug. Meanwhile, the problem of designing a programming language can be understood as optimizing a utility function which balances performance with simplicity. In this work, I will attempt to explore some proposed methods for measuring software complexity and examine how the choice of programming language can impact the complexity of a piece of software.

Following is a partial table of task complexity metrics, including Chaocipher's score of 6.351905.  It should give you an idea of the range of complexities:

Task Mean Complexity
Shell-one-liner 0.045517
Halt-and-catch-fire 0.216667
Hello-world-Text 0.298814
Hello-world-Standard-error 0.326364
Literals-Floating-point 0.327647
Include-a-file 0.363902
. . . .
Inverted-syntax 1.000417
HTTPS 1.028065
Increment-a-numerical-string 1.047647
Secure-temporary-file 1.076923
Simulate-input-Mouse 1.103636
Loops-Foreach 1.104643
. . . .
Iterated-digits-squaring 5.037143
Ramer-Douglas-Peucker-linesimplification 5.041875
Morse-code 5.048800
Numbers-which-are-not-the-sum-of-distinct-squares 5.049000
Shortest-common-supersequence 5.055833
Safe-primes-and-unsafe-primes 5.070870
IBAN 5.078462
Levenshtein-distance 5.106383
. . . .
Permutations-Derangements 6.217000
Long-multiplication 6.325294
Matrix-chain-multiplication 6.330417
Knapsack-problem-Bounded 6.346364
Chaocipher 6.351905
Perlin-noise 6.420714
Periodic-table 6.445556
Koch-curve 6.448750
. . . .
Snake 19.191875
Peaceful-chess-queen-armies 20.200588
Hunt-the-Wumpus 20.332667
One-time-pad 20.565000
Rare-numbers 22.071579
P-Adic-square-roots 24.320000
K-means++-clustering 25.553333
P-Adic-numbers-basic 26.784000
P-value-correction 28.286000
Minesweeper-game 31.507647

Publication: The true and the real: Joyce’s ‘world‑likeness (in Hungarian)

Image of András KappanyosI came across the following paper (2024), written in Hungarian, titled "The true and the real: Joyce’s ‘world‑likeness".  Written by András Kappanyos, the author is a Hungarian literary historian, translator, and university professor.  His paper relates to John F. Byrne, his relationship with Joyce, and Byrne's Chaocipher.

Copilot AI Summary of the Paper

I asked Copilot AI to summarize Kappanyos's paper.  Here is its summary.

The study examines how James Joyce built his narrative universe almost entirely from real people, places, and events he observed in Dublin before leaving Ireland at age 22. Rather than inventing stories from imagination, Joyce treated memory as his creative engine, transforming lived experience into literature. The document shows how Joyce’s works—from the early epiphanies through *Dubliners*, *A Portrait of the Artist as a Young Man*, *Ulysses*, and *Finnegans Wake*—reuse, refine, and recombine autobiographical material, gradually compressing and stylizing it into a coherent fictional world. As the author notes, Joyce “22 éves koráig emlékeket és benyomásokat gyűjtött Dublinban, majd élete hátralévő részében… irodalommá dolgozta át ezeket” (“until age 22 he gathered memories and impressions in Dublin, and spent the rest of his life turning them into literature”).

A major focus of the document is Joyce’s three key contemporaries—Stanislaus Joyce, John Francis Byrne, and Oliver St. John Gogarty—whom Joyce metaphorically called his “grindstones” (“köszörűkövek”). Each man influenced Joyce intellectually and personally, and each later wrote his own account of their shared past. These memoirs, written after Joyce became famous, attempt variously to clarify, correct, or counter Joyce’s fictional portrayals. Byrne, for example, recounts how he helped Joyce through a personal crisis in 1909 and later published *Silent Years*, where he describes both Joyce and his own invention, the Chaocipher: “Memoárja 1953-ban jelent meg Silent Years címmel… főművének pedig a Chaocipher… rejtjelezési eljárást tartotta.”

The final section contrasts Joyce’s fiction with these alternative narratives. While Stanislaus and Byrne generally support or contextualize Joyce’s versions of events, Gogarty’s fictionalized memoir *Tumbling in the Hay* attempts to undermine Joyce’s self‑presentation by depicting his alter ego as insignificant and directionless. Yet the document argues that Joyce’s narrative universe ultimately supersedes these competing accounts: his fiction is “valósabb, mint ami ‘valójában történt’” (“more real than what ‘actually happened’”).

Excerpt: Chaocipher-Related Paragraph (Page 17)

Here is a translation of the section relevant to Chaocipher:

"After 1909, Byrne met Joyce two more times: in 1927 and in 1933 he visited the family in Paris, spent a few days with them, and besides reminiscing about old times they talked about new sections of Finnegans Wake. His memoir was published in 1953 under the title Silent Years. Byrne worked mostly as an economic journalist in New York, and he regarded the cryptographic method called the Chaocipher as his major life’s work. Joyce was an important figure in his life, but by no means the central one. When, in the early 1950s, he brought the manuscript of his autobiography to a New York publisher, he himself did not really know how significant it would be for the by‑then already very lively field of Joyce scholarship. It was almost certainly the publisher who suggested that James Joyce’s name should appear at least in the subtitle of the book, since for potential readers this would provide a much more likely point of connection than the cryptographic method demonstrated with numerous examples — but in reality Joyce’s name appears in at most half of the chapters. In those places, however, Byrne undoubtedly plays into the hands of the philologists: like Stanislaus, he also recounts how certain scenes actually happened in real life, some of them not even with Joyce, but with Byrne himself."

William F. Friedman's version of the Yardley-Damen story

This item adds historical perspective to Byrne's contacting Herbert O. Yardley in 1958.  To understand the background, here is an excerpt from my 2011 paper in Cryptologia, "John F. Byrne's Chaocipher Revealed: An Historical and Technical Appraisal", pages 336-337:


Yardley - Damen story about random ciphertextYardley - Damen story about random ciphertext

A reader would be excused for understanding that Yardley had performed the commendable analysis on his own.

It turns out that William F. Friedman had a different version.  In Friedman's copy of Yardley's "American Black Chamber", on page 142 where the story is told, we find the following comment in the margin:

WIlliam F. Friedman's version of the Yardley - Van Damen story

"Yardley came to this conclusion after we at Riverbank had pointed out the peculiarities and stated that it was probably a hoax. W.F.F."

According to Friedman, Yardley repeatedly took credit for cryptanalytic work that had actually been performed at Riverbank Laboratories -- much of it by Friedman himself or under his direction. During the period in which Yardley was associated with Riverbank, Friedman was building what would become one of the most capable cryptographic research groups in the United States.

Friedman’s anger toward Yardley, however, went far beyond questions of credit. His criticism was deep, sustained, and rooted in professional ethics as well as national‑security concerns. He regarded The American Black Chamber as a reckless and damaging disclosure of U.S. cryptographic capabilities. His reaction took many forms: extensive marginal notes in his personal copy of the book, formal complaints within government channels, and increasingly hostile correspondence with Yardley.

Friedman’s objections can be understood in four overlapping dimensions:

•     Ethical - Yardley violated the professional secrecy that cryptanalytic work required.
•     Operational - The book jeopardized ongoing and future U.S. intelligence efforts.
•     Personal - Friedman felt betrayed by a former colleague who had once been part of the same small cryptologic community.
•     Documented - His disapproval survives in annotated books, letters, and official memoranda.

The archival record -- especially Friedman’s heavily annotated copy of The American Black Chamber -- offers a uniquely detailed view of his disapproval. The marginal comment quoted here is only one of many such notes that reveal the depth of his frustration with Yardley’s actions.

"Coded Insights" Website: The Chaocipher

This website attempts to summarzie the history of Chaocipher.  The site succeeds in capturing the history accurately, although lacking in references and links to resources.

Video game "Keep Talking and Nobody Explodes" highlights Chaocipher

In Progress Report #27, I wrote about a website that referenced Chaocipher that completely baffled me.  I couldn't figure out who was referencing Chaocipher in what looked like an online game.

I was therefore delighted to receive an email in February 2025 from someone with a handle of "Timwi" who kindly explained the context.  Below is our correspondence, which sheds light on how Chaocipher appears in the KTANE modding community.

1 February 2025: Timwi to Moshe Rubin

Hi!

I randomly stumbled upon your Progress Report #27 where you ask: “What does this reference here to Chaocipher mean?”, linking to this page titled “On the Subject of Ultimate Cycles”.

What you have found here is a document relating to a video game called Keep Talking and Nobody Explodes (website | Wikipedia). The game has a fan-run modding community of programmers who make “modules” (minigames/puzzles) for the game. Several of those fan-made modules deal with encryption ciphers.

The game consists of a “bomb” that must be “defused”, which really means to solve the modules (puzzles/challenges) on it within an allotted amount of time (before the bomb “explodes”). The player holding the bomb (the “defuser”) will relay information displayed on the modules to the other players (the “experts”) who use manuals such as the one you discovered to “disarm” (solve) each module.

There are in fact three separate modules that involve Chaocipher. They are:

I hope I was able to clear up your confusion!

Timwi


4 February 2025: Moshe Rubin to Timwi

Dear Timwi,

First and foremost, thank you for taking the time to contact me.  Reading your reply and browsing to your links, I now realize there is a whole world of fascinating "Keep Talking and Nobody Explodes" enthusiasts out there - and to think I had no idea <g>.  I just watched the video https://steamcommunity.com/app/341800/videos/ and was sitting on the edge of my seat!

With your permission, in the upcoming Chaocipher Progress Report, I would like to highlight your email and write about the KTANE community.

Thank you so much for taking the time and energy to update me.  You are a true professional!

Best regards,

Moshe Rubin
Jerusalem, Israel
Maintainer of the chaocipher.com website


4 February 2025: Timwi to Moshe Rubin

Thank you for your kind words! Yes, you have my full permission to publish the e-mail that I sent you, and to link to and describe KTANE including my repository of manual pages.

I should note that the videos you saw on Steam are quite old. KTANE started out (and is still marketed as) a party game; the modules in the base game are easy once you understand them and the novelty value wears after a while. The modding community has taken the game way into the stratosphere by creating modules that are way harder, far more serious and more elaborate. One reasonably well-known proficient defuser in the community is Zefod42 on YouTube who has uploaded many videos of their successful defusals of large bombs that include more modern, difficult modules. Most of his videos are showing the defuser side, but here’s one where he’s the expert and you can see him deal with manuals and calculations and all the gritty stuff.

Another way that you can get an idea of how KTANE modules work is by looking at tutorial videos that fans of the game have made to explain them. Here’s a tutorial video for Cream Cipher and here’s one for Ultimate Cycle, two of the modules that I mentioned that include Chaocipher in their gameplay. The third one, Cipher Machine, is so extensive that the tutorial video doesn’t cover all of it.

Fun talking to you!

Timwi

This exchange opened my eyes to the vibrant KTANE modding community and its creative use of Chaocipher. It is remarkable to see the cipher appear in such an unexpected modern context.

Chaocipher in Klaus Schmeh's "Codeknacker gegen Codemacher" (Codebreakers against Codemakers)

Klaus Schmeh is a German computer scientist and one of the world’s most prolific writers on cryptology. He has authored numerous books, articles, and papers, and is widely recognized for his accessible writing on historical and modern encryption.

It was therefore with great interest that I ordered his German language book, "Codeknacker gegen Codemacher" (Codebreakers against Codemakers).  Schmeh covers the Chaocipher system on pages 237-240, which I have translated using Copilot AI.  The following is Schmeh’s interpretation of Byrne’s work. While his narrative is engaging, it includes several evaluative statements that reflect his own perspective.

Chaocipher: A 90-Year-Long Misunderstanding

In James Joyce’s novel Portrait of the Artist as a Young Man, there is a protagonist named “Cranly.” The model for this fictional character was Joyce’s friend and fellow student John Byrne (1880–1960). This John Byrne entered the history of cryptology by inventing an encryption device that occupied him and many others for decades: the “Chaocipher” (Rubin, 2011).

Unfortunately, Byrne did just about everything wrong that he could have. He barely engaged with the fundamentals of cryptology yet considered himself clever enough to develop a revolutionary encryption method. He vastly overestimated the quality of his Chaocipher and even believed it to be unbreakable. He kept the workings of the Chaocipher secret until his death, although the security of a method should never depend on its secrecy. In other words: Byrne was the embodiment of the Dunning-Kruger effect.

Byrne, who emigrated to New York in 1910, invented the Chaocipher in 1918. Until then, he had little to do with cryptology. He revealed that the otherwise secret mechanism of his device was a relatively simple construction that fit entirely into a cigar box. The Chaocipher thus competed with devices like the Enigma or the Hagelin machines—a hopeless endeavor.

Byrne offered his invention to several U.S. agencies, including cryptology genius William Friedman, who examined the method. But no one wanted the Chaocipher. None of the experts pointed out its weaknesses—a common tactic when one wants to keep their expertise to themselves. Some reviewers even gave moderately positive feedback. This was likely strategic: even stating that a particular encryption device was poor could be valuable information to an adversary. But Byrne didn’t see through this and continued to believe he had invented something extraordinary.

Byrne invested a lot of time in the Chaocipher. Like many figures in cryptology history, he was multi-talented and curious. In his youth, he was one of Ireland’s best chess players and later became a respected journalist. It probably would have been better to focus on those pursuits, but the Chaocipher was more important to him. In 1953, Byrne published his autobiography Silent Years, citing the Chaocipher as the main reason for the book. He still didn’t reveal how the method worked but published numerous encrypted texts along with their plaintexts. He even offered a $5,000 prize to anyone who could crack the messages within three months. Byrne died in 1960 without receiving the recognition he had hoped for.

In 1973, crypto-historian Louis Kruh was looking for interesting topics for a cryptology event and came across the Chaocipher. Since John Byrne was long deceased, he contacted Byrne’s son, John Byrne Jr., who was well acquainted with the workings of the Chaocipher. Like his father, he refused to reveal anything about it. He also overestimated the method’s quality and hoped to commercialize it—even though electronic encryption machines already existed.

Kruh remained in contact with Byrne Jr., and in late 1989, the latter finally made a concession. Kruh and his colleague Cipher Deavours were allowed to examine the device. They later expressed cautious approval of the Chaocipher. From today’s perspective, it’s likely they weren’t being truthful—perhaps to avoid offending Byrne Jr.

In 2009, Israeli computer specialist Moshe Rubin launched a website to collect information about the Chaocipher (Rubin, 2020). This significantly increased interest in the device. In 2010, Byrne Jr. finally relented: he published the workings of the Chaocipher, bringing the truth to light after more than 90 years. The Chaocipher turned out to be a system involving two cipher disks that had to be rotated after each letter during encryption and decryption (see Fig. 2.89). A unique feature was that the operator had to rearrange the letters on both disks before each read.

As nearly all experts had expected, the Chaocipher was far from revolutionary. What Byrne considered unbreakable was actually solvable if one understood the method. Moreover, the constant rearranging of letters on the disks was extremely cumbersome.

So the Chaocipher was not only less secure but also more unwieldy than the Enigma, which was developed around the same time. By the time Byrne published his autobiography in 1953, far superior encryption machines already existed. In 1989, when Kruh and Deavours examined the device, computers had long since entered the field of cryptology. The hope of making money with a two-disk cipher machine was nothing more than a bad joke. In the end, the Chaocipher was just a 90-year-long misunderstanding. Fortunately, this skeleton from the cryptology closet has now been laid to rest.

While Schmeh’s overview is engaging, several factual inaccuracies or oversimplifications appear in the text. These include

AI-Generated Podcasts Highlighting Chaocipher

Numerous websites offer AI-generated audios / podcasts as part of their features or advertising pitch.  Here I present two such AI podcast audio files.  Both audio files speak about my 2011 Cryptologia paper, "John F. Byrne's Chaocipher Revealed: An Historical and Technical Appraisal".

The first podcast, sent proactively in an email by academia.com, presents a single narrator talking about the paper.  The presentation is a good one, and is a sample of what AI can do in this area.

The second podcast was generated by me using Google's NotebookLM, a superb product for people who need to analyze existing papers and textual sources.  I uploaded my paper and requested an Audio Overview.  The result is two moderators, male and female, discussing the paper.  The technology is impressive, though both podcasts mispronounce “Chaocipher.”

These AI‑generated summaries show how Chaocipher continues to appear in new technological contexts, often in ways Byrne himself could never have imagined.

Chaocipher Encryption / Decryption Websites

Here are two websites that provide users with an online Chaocipher encrypt/decrypt tool:
These tools present you with an interesting experiment: encrypting / decrypting a string of one character (e.g., "aaaaaaaa...").  Encrypting or decrypting a stream of identical characters exposes a structural quirk of Chaocipher: the evolving alphabets become partially visible. This does not immediately yield a practical attack, since the cipher cannot be driven arbitrarily without plaintext, but it does reveal internal state information that would normally remain hidden.

Here we present encrypting and decrypting with a string of A's, for both tools.  Notice how portions of the left / right alphabet sequences show up when encrypting / decrypting a stream of identical characters.

Encrypting stream of A's with converterfu.com

Decrypting stream of A's with converterfu.com

Encrypting stream of A's with cnvrtr.com

Decrypting stream of A's with cnvrtr.com

Grokipedia's Webpage for Chaocipher

Grokipedia -- an AI‑generated encyclopedia powered by Elon Musk’s Grok model -- automatically produces articles on a wide range of topics.  The Grokipedia Chaocipher entry is an accurate and thorough exposition of Chaocipher.

The one drawback with Grokipedia's process today is its inability to integrate diagrams and pictures, due to copyright issues.  I contacted Grokipedia and offered my own Chaocipher diagrams free to use, with no strings attached.  I received the following reply:

Grokipedia rejection of Chaocipher diagrams

The Irish Times: A Piece about John F. Byrne

Another modern reference to Byrne appears in a January 2017 Irish Times article about John F. Byrne titled "Number Seven’s Son – An Irishman’s Diary about the cryptographer and friend of Joyce, John Francis Byrne".  The article is quite original, providing interesting tidbits about Byrne and Joyce.  I found the following of historical value:

As the decades passed, he remained admirably quiet about his former friend, whose work had spawned an academic industry. But in 1953, he delivered the manuscript of his memoir to a Joycean scholar in the New York Times, who at first had no idea of his identity.

Joycean witness

After the visit, by chance, the NYT man was having lunch with Frank O’Connor, who told him excitedly that Byrne was the last important Joycean witness still in the wild, and that  the manuscript should be protected zealously, or Joycean experts would “tear you apart”.

This article is a reminder that Byrne’s life continues to attract interest not only from cryptologists but also from literary historians and journalists.


Byrne Genealogical Information

This section highlights recent genealogical findings and historical sources related to John F. Byrne and his extended family

The Byrne Identity: The Wicklow Background of Joyce's Cranley

Ken Hannigan has once again produced an invaluable paper about John F. Byrne and his connection to Wicklow County in Ireland.  This paper, titled "The Byrne Identity: The Wicklow Background of Joyce's Cranley", was published in the Journal of the Wicklow Historical Society, Vol. 6, No. 5, June 2023.  The Byrne Identity examines the Wicklow origins and family history of John Francis Byrne (1880–1960) -- James Joyce’s close friend and the real‑life model for Cranly in A Portrait of the Artist as a Young Man. Drawing on parish records, burial registers, and Byrne’s own autobiography, the article reconstructs the Byrne and Fleming families’ migration from rural Wicklow to Dublin and the social conditions that shaped Byrne’s early life.

The paper situates Byrne within the broader pattern of 19th‑century Wicklow–Dublin migration, highlighting themes of poverty, high child mortality, and shifting economic opportunities. It also explores the family connections that brought Byrne to spend his childhood summers in Wicklow -- experiences that influenced both his personal identity and Joyce’s literary portrayal of him.

Hannigan concludes with generous remarks about The Chaocipher Clearing House:

"Thanks once again to Moshe Rubin for sharing the results of his indefatigable investigations into J.F.Byrne and his Chaocipher.  Moshe’s website, The Chaocipher Clearing House (http://chaocipher.com)  is an amazing collaborative online resource and has been used extensively in the preparation of this and the previous article on Byrne. It is the monument that Byrne might have craved had he been able to envisage it – and he probably did."

John F. Byrne Family Tree in WikiTree

WikiTree provides a valuable family tree about John F. Byrne.  The WikiTree entry is especially useful because it consolidates primary sources -- census records, birth registries, and passport applications -- into a single, well‑organized profile.  Of special interest are the references on that page:

John F. Byrne and Gertrude Rodman: New York City Marriage Listing

As a Catholic, Byrne did not obtain a civil divorce from his first wife, Mary Alice (née Headen) Byrne.  For years, his paramour, Gertrude Rodman, lived in the same household together with Byrne and Mary.  Some online sources have wondered if Byrne ever married Rodman. The following links to the online New York City Marriage Index Registry for 1958 prove that he indeed did:
Records indicate that Byrne married Gertrude Rodman in 1958, despite no evidence of a prior divorce from Mary Alice.  Byrne's son John (1929-2008), the husband of Patricia (Neway) Byrne, was Gertrude's biological son.

Mary Alice (Headen) Byrne's grave

Here is a link to the gravesite of John F. Byrne's first wife, Mary Alice (née Headen) Byrne.

Patricia Byrne (née Neway) Obituary

TheatreAficionado.com is a small, niche website focused on theatre and performing arts.  In 2012 it featured an obituary of Patricia (née Neway) Byrne (1919-2012), the wife of John Byrne and John F. Byrne's daughter-in-law.

TheatreAficionado.com featured an obituary for Patricia (née Neway) Byrne (1919-2012), an acclaimed opera singer and the wife of John Byrne (1929–2008). The obituary provides additional personal context about the Byrne family’s later years.


These genealogical sources continue to shed light on Byrne’s personal history, offering a fuller picture of the family context behind the Chaocipher story

Copyright (c) 2009-2026 Moshe Rubin
Created: 19 April 2026
Last Updated:

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