# Revisited: The Ivory Coast cryptogram

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

Earlier this year, I was contacted by Frank Schwellinger, 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.

### The Ivory Coast cryptogram

Frank Schwellinger’s book presents a collection of 50 puzzles, each one being connected to a certain country. Puzzle #2 is based on a background story situated in the African country, Ivory Coast. The challenge is about the following image:

Source: Schwellinger

The solution of this challenge is not provided in the book nor, according to Frank Schwellinger, has a reader ever found it. In July this year, I introduced this cryptogram in a blog post. There were many interesting comments, but in the end, my readers couldn’t decipher this message, either.

###### ♦♦♦♦♦♦♦♦♦ Coming December 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”

### A summary and new hints

Frank Schwellinger has now provided me a summary of the discussion about the Ivory Coast cryptogram, as well as two new hints. Here’s what he sent me (he wrote in German, I added an English translation):

1) Der Klartext besteht aus einem Satz.

1) The plaintext consists of one sentence.

2) Dieser Satz bezeichnet ein Lösungswort und zwar völlig eindeutig. Dieses Wort wird gesucht.

2) This sentence designates a solution word completely unambiguously. This word is searched for.

3) Narga liegt mit seinem Kommentar #6 vollkommen richtig. Der Klartext wurde zuerst einfach im Windings3 Font dargestellt. Dass Narga damit auf eine typisch deutsche Buchstabenhäufigkeit stößt, ist daher verständlich und auch so beabsichtigt, damit unter den unzählig vielen Ansatzmöglichkeiten darauf geschlossen werden kann, dass man sich auf der richtigen Spur befindet. Der gewählte Font war zwar ungewöhnlich aber wurde mit alten MS Office-Versionen standardmäßig ausgeliefert, so dass es genug Menschen geben muss, die ihn schon einmal gesehen haben. Den Font kann man sich übrigens auch kostenlos von diversen Seiten mit freien Fonts herunterladen. Narga liegt auch richtig damit, dass das Leerzeichen durch das “-“-Zeichen ersetzt wurde. Seine Vermutung, dass eine Transposition folgt, ist ebenfalls korrekt. Ich habe jedoch nicht geprüft, ob seine Transkription korrekt ist. Da der Font bekannt ist, kann das jeder selbst prüfen.

3) Narga is absolutely right with his comment #6. The plaintext was first simply displayed in the Windings3 font. It is therefore understandable that Narga encounters a typical German letter frequency, and this is also the intention, so that among the countless possible approaches it can be concluded that one is on the right track. The chosen font was unusual but was delivered with old MS Office versions by default, so there must be enough people who have seen it before. You can download the font for free from various sites with free fonts. Narga is also correct in that the space character has been replaced by the “-” character. His assumption that a transposition follows is also correct. But I did not check if his transcription is correct. Since the font is known, everyone can check that for himself.

4) Das Kryptogramm ist schwierig aber lösbar. Das ist ein wichtiger Hinweis, den viele Leser außer acht lassen. Es würde keinen Sinn machen, in einem Rätselbuch ein unlösbares Rätsel abzudrucken. Es hat sich ein Leser darüber beklagt, dass es so viele Möglichkeiten gäbe und es sich auch um eine Maskierung handeln könne aber wenn ich bereits die zu meiner Sprache passende Buchstabenhäufigkeit habe, ist Transposition wahrscheinlicher als Maskierung und meine Möglichkeiten, die Verschlüsselung zu verkomplizieren sind begrenzt, wenn der Algorithmus unbekannt ist und die Chiffre lösbar sein soll. Sobald der Ansatz zu kompliziert ist, ist er falsch, solange er zu einfach ist, ist er ebenfalls falsch. Bei der Transposition kann es sich ebenfalls nicht um irgendeine beliebige Permutation der Zeichen handeln, weil dies viel zu schwierig und wahrscheinlich sogar unlösbar wäre. Folglich muss diese Transposition einem bestimmten System folgen. Manchmal hilft der gesunde Menschenverstand unter unzähligen Möglichkeiten, die richtige zu finden.

4) The cryptogram is difficult but solvable. This is an important clue that many readers disregard. It would not make sense to print an unsolvable puzzle in a puzzle book. One reader complained about the fact that there are so many possibilities and it could be a masking but if I already have the frequency of letters matching my language transposition is more likely than masking and my possibilities to complicate the encryption are limited if the algorithm is unknown and the cipher should be solvable. As soon as the approach is too complicated it is wrong, as long as it is too simple it is wrong as well. The transposition cannot be any arbitrary permutation of the characters either, because this would be much too difficult and probably even unsolvable. Thus this transposition must follow a certain system. Sometimes common sense helps to find the right one among countless possibilities.

5) Dies ist ein neuer Tipp, der sich auf Tipp 4 stützt: Natürlich könnten die Pfeile eine geometrische Bedeutung besitzen, die für die Transposition eine Rolle spielt. Dem ist aber nicht so. Die Geometrie der Pfeile besitzt keinerlei Bedeutung. Sie dienen nur der Verwirrung.

5) This is a new tip based on tip 4: Of course, the arrows could have a geometrical meaning that plays a role in the transposition. But this is not the case. The geometry of the arrows has no meaning. They only serve to confuse.

6) Ich habe die Leser auch immer wieder dazu aufgefordert “herauszufinden”, was dieses Rad denn darstellen soll, weil Kontextinformationen zu besitzen, nie verkehrt sein kann. Ich war sehr überrascht, wie lange es dauerte, bis ein Leser auf die Idee kam, bei Amazon mit einem “Blick ins Buch” nachzulesen, dass es sich um “das geheimnisvolle silberne Sonnenrad” handelt. Damit kann man versuchen nach einem “guessed plaintext” zu suchen, was dann ein Leser auch zumindest versucht hat.

6) I also asked the readers again and again to “find out”, what this wheel should represent, because having context information can never be wrong. I was very surprised how long it took a reader to come up with the idea to “look into the book” at Amazon to find out that it is “the mysterious silver sun wheel”. So you can try to search for a “guessed plaintext”, which a reader at least tried to do.

7) Dies ist ein zweiter neuer Tipp, der sich jetzt auf Tipp 6 bezieht: Der Teilstring “sonnen” kommt mindestens einmal im Klartext vor.

7) This is a second new tip, which now refers to tip 6: The substring “sonnen” occurs at least once in plain text.

Can a reader solve the Ivory Coast cryptogram with this summary and these new hints? If so, please leave a comment. Frank Schwellinger has promised to award a copy of his book to the first successful codebreaker. Good luck!

Further reading: Ron Rivest publishes new time-lock puzzle

## Kommentare (19)

1. #1 TWO
8. Oktober 2020

Sonnenstunden

2. #2 TWO
8. Oktober 2020

It seems to be written in concentric circles.

The inner circle contains the word Sonnen and the word Die

A real eclipse of reasoning

3. #3 TWO
8. Oktober 2020

The Dark side of the Moon could be involved.

Der große Auftritt im Himmel

4. #4 frank
8. Oktober 2020

@TWO

“sonnenstunden” is just a guess and I’m sorry, but this word is neither the solution nor is it contained in the plain text.

You also write “The inner circle contains the word Sonnen and the word Die”

If you try to decipher each circle separately and independently from the others, it will not work.

5. #5 TWO
8. Oktober 2020

@Frank

That is two extra hints for the blog readers.

Most likely yoou are transposing from the outside towards the centre of the system.

6. #6 frank
10. Oktober 2020

@TWO

Of course I can’t tell you exactely how the transposition is done but as even a further hint I will give you a valuable detail of the algorithm behind this cipher.

The algorithm starts with a circular disc prefilled with blanks ‘-‘. No blanks are coming from the plain text. The words from the plain text are inserted character by character (according to some system) without any blanks separating them from each other. The blanks ‘-‘ that can be found on the disc are just positions which are left over, after the character insertion process of the plain text is completed.

Now good luck!

7. #7 TWO
10. Oktober 2020

Thank you Frank

I will take look at it but the German language, the beautiful language of Goethe and Schiller is not my specialty so I am afraid the puzzle needs a German sover.

My first impression when I saw your mysterious Sun wheel was that you witnessed a solar eclipse while on Holiday in CI.

Whatever, it is a work of art and speaks to me.

8. #8 frank
10. Oktober 2020

@TWO

I am sorry that German language might be a difficulty for you. Maybe one day I shall construct a crypto riddle in English especially for the readers of this blog and maybe Klaus Schmeh will publish it then.

I indeed witnessed an impressive total solar eclipse with 100% of coverage in the year 1999 in the German city of Karlsruhe.

But this riddle is not inspired by a solar eclipse, although it is somehow related to the sun.

And thank you for liking my “work of art”.

9. #9 frank
15. Oktober 2020

As very slowly but surely Santa Clause and also Christmas Time are coming, I decided to give away additionally to my book “Warum gibt es kein Bier auf Hawaii” also a free printed copy of my book “Das neue Haus vom Nikolaus” (which translates to “The new house of Santa Claus”) to the first person posting the solution of this riddle in this blog thread.
Altough “Das neue Haus vom Nikolaus” only contains mathematical riddles, many people who like breaking codes also like mathematical riddles.
To find out if you like this book at all, you can go to Amazon

https://www.amazon.de/neue-Haus-Nikolaus-mathematische-Weihnachtsr%C3%A4tseleien/dp/3499627191/ref=sr_1_1?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=das+neue+haus+vom+nikolaus&qid=1602784326&sr=8-1

If you are less interested in mathematical puzzling, you still can give away the book as a present for Santa Claus or for Christmas to someone who likes puzzling – if you win it.

Of course, the winner may choose, if he wants to get his books autographed or not.

Furthermore, if wished, the winner will get a handwritten note in “Warum gibt es kein Bier auf Hawaii” which states that he is the first person ever who solved this riddle and how many years it took until it had been finally solved. The statement can be given either in English or in German.

OK. I like riddling and breaking ciphers myself and I know that cipher breaking makes more fun if there is some kind of a treasure. So, if anybody can post the correct solution within this year, I will also give a German silver coin over the buying value of 10 Euros (official coin and valid for payments in Germany only) as a very small silver coin treasure.

If the right solution arrives 2021 or later, there will be only the books as trophies.

I wish you good luck and success.

10. #10 Magnus Ekhall
Borensberg
25. Oktober 2020

I had a closer look at this but have still not managed to figure out the solution.

A few thoughts:

We know that Frank started out with an empty wheel with 26 * 4 spaces, then used an algorithm to place the cleartext letters in their place, one by one. The algorith is the actual key here, and it can work in two possible ways: Either it will by design always select an unused space for the next character, or it has to be able to deal with the fact that it may end up on a “used” space and how to move from there to an empty space. Given the distribution of the 24 empty spaces in the cryptogram I tend to lean towards the latter: that the algorithm has a way to handle already occupied spaces.

Another observation, which may or may not be relevant, is that the wheel has 26 columns. The German alphabet has 26 letters if you disregard ß and the umlauts. Is that a coincident? The ciphertext does not have any umlauts or ß. Maybe this is simply a result of the windings font not having umlauts.

We know that “SONNEN” appears somewhere in the message. Given the number of S, O, N and Es in the message it is possible to spell out “SONNEN” in more than 150000 different ways.

11. #11 Narga
25. Oktober 2020

I also have not given up, yet 🙂 But I ran out of ideas a while ago. Hint #3 got me thinking a lot. If the transposition is not a super Hard one but solvable as frank said, why couldn’t he then quickly check my transcript by just looking at it, following the letters of the solution?
From that I concluded that my formatting in four lines is far from what we need and the algorithm probably needs another input format?
My impression is that from the available letters and the hints given, LOESUNGSWORT could be part of the solution.

12. #12 Gerd
25. Oktober 2020

According to frank, there is a certain system behind the transformation. However, it seems to me that there ist no unknown keyword or similar behind that. Also it seems the system is not regular or symmetric, as someone would have solved it up to now. So maybe the system depends on the cleartext itself, i.e. each letter of the cleartext indicates where to put the next letter.

13. #13 Magnus Ekhall
Borensberg
25. Oktober 2020

Gerd: I have tried some systems like that, with the crib “SONNEN”. Unfortunately it did not lead to any breakthrough.

A complicating factor can be that we do not know where the message starts and where it ends. But I guess it is safe to say that all the spaces are at the end of the message.

14. #14 frank
25. Oktober 2020

At this point I will not give you many more specific hints but some of your recent ideas from the last 4 postings are getting you closer to the solution. Some of these ideas I would even consider as breaktroughs. You only have to dare to follow them and select and combine the right ones. The cipher starts to tumble now 😉

@Narga: The only reason I don’t check your transcription is, I’m just too lazy to do it. I don’t like to check a cipher by eyesight and possibly make a mistake by not being concentrated enough. There are no conclusions whatsoever that can be drawn from that.

good luck!

15. #15 Magnus Ekhall
Borensberg
28. Oktober 2020

Hello,

I think we finally broke it!

The solution is “Sun Horse” or “Sonnenpferd” in German.

The full clear text is:
“gratulation sie sind ein wahrer meister der codeknackerkunst die loesung lautet sonnenpferd”

The algorihm is as follows:
For each clear text letter, the corresponding number of steps (A=1, B=2…) is taken diagonally, cyclically. This new postiion determines the location of the next letter. If there already is a letter in this position, move clockwise until you find an empty space.

My colleague Patrik Almqvist made the final discovery with the diagonal movement but we have discussed this for some time now.

16. #16 frank
28. Oktober 2020

————————Tataaaa!———————-

Finally the cipher has been solved after 8 and 1/2 years by Magnus Ekhall and (Patrik Almqvist)

So Magnus is the winner and entitled to claim the “trophy”.

Congrats Magnus, you did a great job.

I hope you enjoyed this riddle.

————————–The contest is now closed ———————————-

17. #17 Narga
28. Oktober 2020

Amazing! Congratulations, Magnus and Patrik!

18. #18 frank
28. Oktober 2020

@Narga:

I want to thank you too for participating in this contest and some very good postings including your recognition of the wingdings3 font. As I want to thank all the other readers who contributed their ideas.

19. #19 Magnus Ekhall
Borensberg
28. Oktober 2020

I agree: there is no way we could have solved this unless we had the good insights and comments from the blog readers, as well as the clues from Frank.