A challenge cryptogram from a 2012 puzzle book is still unsolved. The author will award a book copy to the first one who breaks it.

Are you interested in the Voynich Manuscript? Together with Richard SantaColoma, I will give a webinar about The Book Noone Can Read tomorrow (Saturday, July 11, 2020) at 6pm German time (1600 GMT). The talk, which is organized by Bob Saltzman from the Crypto Collectors Group mailing list, is open for everybody and free of charge. If you want to watch it, send me a mail, then I will forward you the login data.


Revisited: The D’Agapeyeff cryptogram

Let’s now come to another book. One of the most popular unsolved crypto mysteries is known as the D’Agapeyeff cryptogram. It is a challenge ciphertext printed on the last page of the 1939 book Codes and Ciphers written by the Russian-born Briton Alexander D’Agapeyeff.


Source: book cover

The D’Agapeyeff cryptogram was meant to be solved by the readers of the book, but apparently this never happened. Alexander D’Agapeyeff admitted that he had forgotten the solution himself. In later editions of the book, the cryptogram on the last page was omitted. For more information, check my blog post from 2017.

Meanwhile, the D’Agapeyeff cryptogram has become a major crypto mystery, mentioned in many “top ten unsolved ciphers” lists, for instance the following one presented in a video on YouTube. MysteryTwister C3, a web portal dedicated to codebreaking puzzles, has a D’Agapeyeff challenge in the X section (X stands for unsolved). Here’s the English version, here’s the German one. I am the author of this challenge, by the way.

♦♦♦♦♦♦♦♦♦ Coming November 2020 ♦♦♦♦♦♦♦♦♦♦♦♦♦

“One of the most helpful guides outside the NSA to cracking ciphers. But even if you don’t become a codebreaker, this book is full of fascinating crypto lore.”

Steven Levy, New York Times bestselling author of “Crypto, Hackers, and Facebook: The Inside Story”


The Ivory Coast cryptogram

Earlier this week, I was contacted by German book author Frank Schwellinger, like me a computer science alumnus from the University of Karlsruhe.

Frank is the author of the 2012 book Warum gibt es kein Bier auf Hawaii? (“Why is there no beer on Hawaii?”). The title is an allusion to a famous German drinking song that denies the existence of a popular alcoholic beverage in the USA’s only island state. Check here for a video of this musical masterpiece.

Frank Schwellinger’s book presents a collection of 50 puzzles, each one being connected to a certain country. Some of the challenges are crypto-related. For instance, the first puzzle of the book is about an easy-to-solve steganographic message:

Source: Schwellinger

Can a reader find the name of the city hidden in this picture?

Challenge #2, which is a lot more difficult, appears to be cryptologic in nature, too. The background story is situated in the African country, Ivory Coast. The puzzle is about the following image:

Source: Schwellinger

Can you decipher the symbols on the wheel? According to the book, the solution is a German word. If this is correct, the plaintext is much shorter than the ciphertext.

Just like the D’Agapeyeff challenge cryptogram, Frank Schwellinger’s Ivory Coast ciphertext was never solved by his readers. However, contrary to D’Agapeyeff, Frank still knows how his ciphertext can be decrypted.

Can a reader solve the Ivory Coast cryptogram? If so, please leave a comment. Frank Schwellinger has promised to award a copy of the book to the first successful codebreaker. Good luck!

Further reading: Ron Rivest publishes new time-lock puzzle

Linkedin: https://www.linkedin.com/groups/13501820
Facebook: https://www.facebook.com/groups/763282653806483/

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Kommentare (35)

  1. #1 Margot Pyrc
    10. Juli 2020

    The city in picture 1 is the capital of baguettes…

  2. #2 Kerberos
    11. Juli 2020

    The ivory coast puzzle
    looks like some nearly circular disk (paper?) is placed
    on top of a circular saw blade with tungsten carbide
    What about the (irregular looking) dots close to the
    circumference of that paper?
    Maybe those are the code?

  3. #3 Gerd
    12. Juli 2020

    The symbols on the wheel are arrows from a certain range of the unicode character chart. See https://www.unicode.org/charts/. Maybe this is a clue?

  4. #4 frank
    15. Juli 2020

    @Margot Pyrc: Seems like you are right 🙂


    I think it’s fair to say that these dots are only decorative in nature and have absolutely nothing to do with the code. I didn’t even consider, somebody could try to interprete those dots. This is a puzzle without any steganographic elements. This is pure cryptography. Don’t waste your time with the dots.

  5. #5 Hias
    15. Juli 2020

    Bei Amazon ist unter den Rezessionen zu lesen:

    „Und bereits im zweiten Rätsel geht es darum, mittels des Euklidischen Algorithmus den größten gemeinsamen Teiler mehrerer Zahlen zu ermitteln.“

    Wenn dieser Tipp richtig ist würde das bedeuten jede Zeile ist eine Hexadezimalzahl (weil 16 verschiedene Symbole). Nun muss man erraten welches Symbol welche Zahl darstellt und dann zeigt der größte gemeinsame Teiler die Lösung?! Viel Arbeitsaufwand für ein Rätsel dieser Art.

  6. #6 Narga
    15. Juli 2020

    To me this looks like the Wingdings3 font. If you “translate” that back to normal characters, you end up already with a typical German letter frequency (“-” as space). Then it seems a transposition is following but I couldn’t find the right method.

    Here is my transcription (starting from top, clockwise, outside to inside):

  7. #7 frank
    16. Juli 2020


    Der Kommentar bei Amazon bezieht sich auf ein anderes Rätsel des Buches. Die Rätsel besitzen außer der Reihenfolge, in der sie im Buch gedruckt erscheinen, auch eine davon abweichende logische Reihenfolge in der sie gelöst werden sollten. Die Lösung eines Rätsels ergibt immer, welches logisch das nächste Rätsel (repräsentiert durch ein Reiseziel) sein soll. Daraus ergibt sich eine Art Rätsel-Schnitzeljagd. Wäre die Druckreihenfolge der Rätsel dieselbe, wie die logische Reihenfolge, dann gäbe es ja gar nichts mehr zu rätseln, denn das im Buch jeweils folgende Rätsel würde bereits die Lösung des vorhergehenden verraten.

    Das Elfenbeinküsten-Rätsel stellt zwar das zweite Rätsel in der Druckreihenfolge der Rätsel dar, während sich der Kommentar auf Amazon aber auf das zweite Rätsel in der logischen Reihenfolge bezieht.

  8. #8 Hias
    16. Juli 2020



  9. #9 hattadone
    23. Juli 2020

    On the blade are 26 sectors with columns of 4 symbols. I was thinking that maybe the combination of 2 of those could represent a letter, so part of the symbols would represent the alphabeth, some the hidden message. Unfortunately neither the outer 2 nor the inner 2 rows only have unique combinations. Maybe the rows are twisted and has first to align them corretly?

  10. #10 Christof Rieber
    26. Juli 2020

    Just an idea for the second cipher:

    All symbols are arrows. Try to draw lines from one arrow to another as long as there is no opposite one ending your line. Like the children games to connect numbers with lines. This should result in some (visual) cleartext. My guess is “Sägeblatt” or “Kreissäge” but don’t have any printer here around to try so please go ahead..

  11. #11 Dampier
    26. Juli 2020

    @Chr. Rieber

    Try to draw lines from one arrow to another

    I tried that, thank you for the suggestion. Unfortunately I could find nothing that made any sense. First of all the rules are unclear: Where to begin? What about double arrows? Where does a triangle point to? What about arrows that point to the outer/inner rim of the disc?

    I think, this solution is far too ambiguous for a concrete crypto puzzle.

  12. #12 frank
    26. Juli 2020

    @Christof Rieber

    Unfortunately neither “Sägeblatt” nor “Kreissäge” is the solution and searching for the solution is definitely no “childrens game”. It is designed to be solvable and it is not designed to take a hundred years to be solved. However – it is by no means easy to solve.

    I do not want to give concrete hints but one piece of advice I could give: Follow the bread crumbs or should I say the pebble stones like “Hänsel” did in the famous fairy tale “Hänsel und Gretel”.

  13. #13 Gerd
    27. Juli 2020

    The hint “follow the pebble stones” sounds to me like only one single symbol is needed for the solution and all other can be ignored.
    My first idea about this is to set the “key symbol” to 1 and all other symbols to 0. So we get a table of 26 columns of 4 bits each. This table assigns a number of 0-15 to each letter of the alphabet. So the table could encode a word of maximum 15 letters, when each letter occurs only once in the word. The test this we need to identify the “key symbol” and the starting column of the alphabet.

  14. #14 Seth Kintigh
    27. Juli 2020

    I started at each black triangle.
    If it pointed left I moved on symbol left, right I moved right.
    If I hit a thin arrow I moved in that direction 1 space left/right/diagonal.
    If I hit a double arrow I tried both routes, and I always ended up in the same place for both routes.
    If I hit a thick arrow with a shadow, I moved 3 spaces that directions (2 would cause an infinite loop)
    I stopped when I hit a black or white triangle.
    I then counted how many spaces I moved:
    25* 0** 25* 1 11 9 21*** 4 0 6****
    *actually -1, ended at white triangle
    ** went straight up. Maybe this is the beginning/end?
    ***actually -5
    ****ended at white triangle

    Using a German alphabet I got UAUAJHSCAE (some of those have umlauts) I don’t know German but I don’t think that’s a word.

    But the fact the paths I drew worked even when I hit a 2-way arrow gave me home I’m on the right path, so to speak

  15. #15 frank
    27. Juli 2020


    Actually the solution does not consist of unique letters only.

    Just use common sense. The cipher had been published in a book. So at any point of time before publishing date, I could have decided to change parts of the book and change the solution of this puzzle too. Wouldn’t be very clever then if I created a cipher that would work with very special plaintexts only.

    However, I like this innovative approach, you took.

  16. #16 TWO
    28. Juli 2020

    My guess ;

    Wagenrucklauftaste mit umlaut

  17. #17 frank
    28. Juli 2020


    Just a guess, why not? But it is not the solution.

  18. #18 frank
    28. Juli 2020

    If you are guessing what this circular shape is meant to represent : it doesn’t represent a typewriter daisywheel nor a circular saw blade.

    It is possible to find out what this shape is meant to be without deciphering it.

  19. #19 TWO
    28. Juli 2020

    It looks like a bicycle or water/turbine wheel maybe a tredmill for a hampster

  20. #20 Gerd
    28. Juli 2020

    Ok, from the shape of the object, I am pretty shure this is what we see here:


    But I feel this doesn’t bring us closer to the solution.

  21. #21 frank
    28. Juli 2020


    I indeed used some circular saw blade picture like this to create the image of this puzzle, but the resulting image isn’t meant to show a saw blade at all. How can you find out, what this object is meant to be? No guessing is necessary. If you use all the information of this blog entry you should know, where you can find this piece of information.

    The intended name of this object is not the solution, but …….. ? 😉

  22. #22 Narga
    28. Juli 2020

    Is it meant to be a bottle cap? For the non-existent beer on Hawaii?

  23. #23 frank
    29. Juli 2020


    Just as I mentioned, no need to guess what it is and even you won’t be able to guess. You’ll have to do some research to find out, how I call this object. It shouldn’t be a big problem to find out, where the name of this object can be found. If you were a special agent reading this thread from the beginning, determined to solve this “case”, what are your ideas where you can find the name of this object? No codebreaking needed to get this name. Just browsing the web and read this name in full plain text. It is ridiculously easy to find. Did you even recognized the title of this thread? Where to expect context information to this cryptogram?

    Although I will usually not comment if some deciphering approaches are correct or incorrect, because cryptograms usually don’t have a builtin help system, I will nevertheless confirm, if anybody comes up with the name of this object. If nobody finds out this name within some weeks, I will tell the name of this object right here.

  24. #24 TWO
    29. Juli 2020

    More information about Ivory Coast : https://www.cia.gov/library/publications/the-world-factbook/geos/iv.html

    The sawblade looks like the compressor stage from an jet engine.
    If you connect the arrows on it you get some sort of map of the stars but no idea which star system it depicts,
    Maybe you ate a hot bar of chocolate or drank a cup of coffee at Starbucks.

    Fun ouzzle

  25. #25 TWO
    29. Juli 2020


    It is not the old joke about Erichs Krönung?

    Back in the 80s I drove often to Berlin and many times I got very sick after a rest stop at one of the Intershops.

    Took some time to figure out that Erich caused it.

  26. #26 frank
    29. Juli 2020

    Haha, this is the first time ever I heard about Erichs Krönung.
    I should be happy not to know it. In the FRG we always had real coffee and in the 80s I was addicted to Coke and hardly ever drank coffee.

    Just like many things Indiana Jones is after,
    the disc shaped object is of fictional nature. You will not find it in the cia factbook.

  27. #27 Gerd
    29. Juli 2020

    Doing something “ridiculously easy” is clicking on “look inside the book” on amazon. That tells us the object is a “Sonnenrad” (sun-wheel). But how to go on now?

  28. #28 Gerd
    29. Juli 2020

    A little more “ridiculous” google work brings up a hint given on the page:


    “Die Symbole stehen für Buchstaben, Satzzeichen oder Leerzeichen. Gleiche Symbole stehen dabei auch für gleiche Buchstaben.”

    Looks like we should go back to #6 and Narga’s wingdings3 decoding, which gives letters and spaces.
    Any Ideas to solve the transposition with the codeword “Sonnenrad”?

  29. #29 frank
    29. Juli 2020


    You did the right thing and yes that’s right, I called it “das geheimnisvolle silberne Sonnenrad” (the mysterious silver sun wheel). But you don’t really expect me to tell you, what to do? do you?

  30. #30 hattadone
    29. Juli 2020


    According to this it is monoalphabetical, containg punktuation marks and spaces. So, we rather look for a sentence pointing to the solution. Riddle in the riddle, i like that.

    Who is visiting the store and asking for the further hints?

  31. #31 hattadone
    31. Juli 2020

    Refering to post #6, the symbols can also be red turned by 180°. (starting reading from the bottom) The turned symbols exist in Winddings 3 as well.

    Replacing the symbols with the turned ones gives the follwing translation (same order as in post #6):


    But it doesn’t seem that german words can be constructed form the result

  32. #32 frank
    31. Juli 2020

    There might be some German words that could be constructed by this transcription



    among others

    FYIO (for readers who don’t know German)

    But that doesn’t mean that this has to be the right approach.

  33. #33 hattadone
    2. August 2020

    I was following the idea, that instead of transpositioning, masking could the solution. With this apporoach the keyword would determine the columns of the wheel as these are exactly 26. So, each letter of the keyword would result in 4 Cleartext letters. In a modified version of the idea, also the row-selection can be masked by a keyword (e.g. letter value mod 4).

    Unfortunately there is still a lot of degree-of-freedom:
    1. you don’t really know where to start on the wheel.
    2. clockwise, or counterclockwise (different alphabets see post #6 + #31)
    3. is the number of rows masked by keyword as well
    3.1 If yes, how? If you now how, which order (starting from inside to outside or the other way around?
    And so on..

    In the following I use the keyword “sonnenrad”, clockwise, an “a” in the keyword selects the “top-Column”. This decodes to:


    A german word could start with “nuss” (nut), but i can’t complete meaningfully.

    Same Keyword, counterclockwise, but a “z” in the keyword selects the top column results in:


    Nothing meaningful here either.

    Now counterclockwise, alternative alphabet, an “a” decodes the “bottom column”:


    I don’t see meaning here as well.

    Finally, counterclockwise, alternative alphabet, “z” decodes the bottom column:


    No obvious meaning here as well.

    So even this approach was not successful, I think it makes sens to the 26 columns into consideration.

  34. #34 Gerd
    2. August 2020

    Looking for a solution based on masking out some columns, I noticed that the inner circle contatins all the letters of “Sonnenrad”. But I could not get a solution from that.

  35. #35 frank
    1. September 2020


    it makes a big difference if a cipher is designed to be breakable or if it is designed to be “unbreakable”. This one is designed to be breakable but it is hard to break.

    Breakable in this case means that the complexity of the “unknown algorithm” cannot be too high, considering the lenght of this cipher.

    If you follow the breadcrumbs then it should be clear that it is not by accident, that what Narga discovered in posting #6 gives you the information that his transcription provides typical German letter frequency.

    So Narga is on the right track. What would be the most simple follow up, if you already have a typical letter frequency?
    Is it masking or is it transposition?

    I decided to give you now this piece of information that there is no masking and that there are no letters that don’t belong to the cipher text. Narga is absolutely right suspecting that there is a transposition that has to be found.

    And this transposition obviously cannot be some totally arbitrary permutation of the letters, as such a cipher would be too difficult to break it.

    Regarding your very good discovery of

    I have to tell you that they don’t have any further hints. It is a pretty long and complicated story why this is the case. Originally I wanted to offer this riddle in cooperation with them but when the store management changed and the new store management showed no interest in this competition, I terminated this cooperation some month ago and I don’t know, why they still have this page online. But they have no further hints. They will not have them in the future and until now, nobody ever solved this cipher.