Weekly Challenges

Challenge 15: June 1918

Here’s Challenge #15 for January 13, 2018.

The year is 1918. You’re a cryptanalyst working for the Allies, and you’ve just intercepted this German Morse-code communication.

--. ..-. -..- --. ..-. .- -.. -..- .- -.. ..-. .- .- -..- / --. .- --. --. --. -.. --. --. -..- -..- --. -.. -..- ..-. / -..- ..-. .- ..-. .- -..- .- -.. --. --. --. .- ..-. -..- / .- -..- --. -.. .- -..- .- -.. -.. -.. .- -..- --. ..-. / .- -..- ..-. -.. .- .- -.. --. ..-. .- .- -.. -..- ..-.

Can you figure out the message and save lives?

Here are some hints:

1. You need to translate these dots and dashes into letters.
2. Is there anything unique about the resulting letters?
3. Who was the first to break this type of cipher?*
4. You’ll need 2 keywords: One for a mixed alphabet and one for a transposition.
5. Before entering the keywords, delete repeat occurrences of any letters. (Ex. NEBEL would convert to NEBL.)
6. I=J
7. The plaintext is in English, not German.

* For purposes of simplicity, this cipher type is an earlier version of the type he cracked. If you are familiar with the two types, it’ll be obvious which it is based on the ciphertext letters. 

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 14: What Futility

Here’s Challenge #14 for December 5, 2017.

Perhaps nothing really matters, but don’t give up hope on this cipher. The method was first used by a political group in the late 1800s to organize terrorism against a regime.

Here’s the ciphertext:

35567034476476485766664594664748705756684736670957649465665776352458564548986557663558749844657733573488382658733566873446583445577738269437474486344658663936896644865435579738476474575780564754567565096456543367648945287773756689444577435834707447854565489865576635395407572476335738703428564358340957349555584888574666443944983437583745467654647645656476662467374744867728545539367057345455587478345685745757805647946478747064456763676686484756473664783428943357387936367743676770363654377546765436946658367074248673676570344677433875884624666467440634268634754767744764377574075636545436348964475476

Hints:

  1. No J.
  2. There is a keyword, and there is a key. Both are last names. One is a real person. The other is a fictional character.
  3. How well do you know your classic Russian literature? I’m thinking of a particular book that popularized a term used in the cipher type’s name.

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 13: Fractionating — SOLVED

Update 2018-01-05: Euchre Mutt is on fire! He’s solved two CodeAWeek puzzles in two days, giving him a very comfortable lead on our High Score list. This challenge remained unsolved for 45 days, which means he is awarded 45 points. To see the solution, go here.

Here’s Challenge #13 for November 21, 2017.

Today, I wanted to learn about ciphers that use fractionation. I decided on a method created by a French amateur cryptographer who spent his days in working in a customs warehouse.

Three hints:

  1. J=I
  2. You need to figure out the keyword and the period.
  3. “Now Morn her rosie steps in th’ Eastern Clime, Advancing, sow’d the earth with Orient Pearle.”

And the ciphertext is:

xmwuv hnmhv hderq
tbkht newsv hnmhv
fpeks ngifq rlqv

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 12: Nigh Impossible

Here’s Challenge #12 for November 8, 2017.

Today, I wanted to learn about homophonic substitution ciphers. These ciphers aim to thwart frequency analysis by assigning multiple ciphertext symbols to each plaintext symbol. The higher frequency of a letter, the more cipher symbols it is assigned. One of the most famous examples of homophonic ciphers is Rossignols’ Great Cipher.

For my homophonic cipher, I wanted to closely-match the frequency of each letter. For example, the letter E has the highest frequency at 12.7 percent. If my cipher used a pool of 100 numbers, 13 of those would represent the letter E. But if I were to use only 100, what would I do with letters such as Z, which have less than 0.1 percent frequency? In order to represent these low frequency numbers, I had to increase my pool to 1000 numbers. So now, the letter E is represented by 127 different characters!

My symbols-to-letters distribution corresponds fairly closely to the characteristic distribution. The letters Q and Z each have 1 plaintext symbol. The letters M and W each have 24. The letter A has 82.

Such a large pool of symbols means that cracking this cipher without hints will be nigh impossible. I’ll reveal a few hints now and occasionally update the post with further clues. I expect this to be the most challenging cipher I’ve yet posted on CodeAWeek.

Each 4 digit number represents a letter in the English alphabet. Here’s the ciphertext:

0385 0376 0275 0591 0106 0856 0957 0894
0808 0997 0830 0801 0511 0556 0648 0995
0295 0587 0756 0686 0983 0169 0207 0353
0111 0447 0545 0168 0162 0294 0632 0475
0937 0951 0996 0444 0549 0410 0652 0939
0701 0936 0312 0231 0770 0186 0898 0458
0374 0507 0479 0423 0017 0198 0323 0550
0306 0233 0460 0702 0625 0583 0708 0004
0524 0205 0305 0037 0038 0677 0351 0465
0299 0092 0753 0293 0018 0775 0100 0654
0311 0938 0108 0612 0496 0118 0495 0698
0665 0201

Notice that no number repeats, which tells you that the plaintext has one or no occurrences of Q and Z.

Here’s the first big hint, which will hopefully take this cipher from nigh impossible to nearly nigh impossible. Here are all 90 symbols for the letter T:

0268 0930 0367 0715 0294 0709 0688 0010 0704 0858 0266 0306 0886 0438 0502 0655 0595 0885 0673 0995 0708 0468 0142 0040 0078 0863 0558 0399 0210 0436 0091 0090 0952 0029 0701 0417 0264 0092 0175 0861 0250 0170 0605 0729 0681 0318 0221 0263 0077 0597 0197 0686 0430 0650 0542 0864 0805 0693 0505 0017 0924 0488 0625 0543 0362 0099 0849 0682 0946 0192 0422 0012 0239 0312 0194 0184 0347 0277 0064 0425 0557 0753 0156 0663 0877 0481 0830 0434 0410 0827

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 11: The Right Type — SOLVED

Update 2017-11-09: We have a winner! Puzzling.Stackexchange user Kayzeroshort solved the puzzle today. It took him 12 days, which means he is awarded 12 points on the Leaderboard. View the solution here.

Here’s Challenge #11 for October 27, 2017.

Today’s cipher is a method I created based on a known method, although it is likely that someone else thought of it before me. Here’s the ciphertext:

YGWCSD QDCHVF WCLEZJ CHCTJQ YUEOYG YSE,GY KYJXDZ KYCYEP IFKWGW
TIHOEP CHRTJR DOCRTU YGY,HB PEDWUC GWU.QD ;WRTDR BESDOY ZDMNUC
SFQDCH RKWCH. POXHQO QFYOY. YPSAYR QFYHYG Y,HGIT YGRT

I’ll give you three clues:

    1. The method is a spinoff of the famous method used to encode Challenge 10.
    2. The punctuation in the ciphertext encodes letters in the plaintext. (There is no punctuation in the solution.)
    3. The following text is not a deciphering tool but a clue that will point you in the right direction. What came after this?
      3 5 7 9 N O P Q R S T U V W X Y Z
      2 4 6 8 . A B C D E F G H I J K L M

New hint! (Updated 2011/11/08): The solve method lies at your fingertips.

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 10: No Cheating — SOLVED

Update 2017-10-22: We have a winner! Stackexchange user M Oehm solved the puzzle today. It took him one day, which means he is awarded 1 point on the Leaderboard. (The puzzle is older than one day, but I just posted it today on Puzzling.Stackexchange, and that’s where he solved it.) Read the solution here.

Here’s Challenge #10 for October 15, 2017.

NO CHEATING

Today’s cipher is a famous cryptographic method known for its economy, ingenuity, and difficulty in cracking. Its inventor created all sorts of cool things, including musical instruments, a timepiece especially useful at the North Pole, and the earliest ancestor of the Oculus Rift. Aside from this cipher, which does not bear his name, he is most famous for co-inventing a means of communicating at long distances.

The key to unlocking the mystery is his name. Good luck!

The ciphertext is:

WXYCNW LAHWNZ WONSNI LEXAPE OSMWOW RCSRQC AZ

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery each week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.

Challenge 9: The Collection — SOLVED

Update 2017-10-21: We have a winner! Stackexchange user Eedrah solved the puzzle today. It took him 13 days, which means he is awarded 13 points on the Leaderboard.

Here’s Challenge #9 for October 7, 2017.

THE COLLECTION

My great uncle from Atlanta died last month, and my family drove there to attend the funeral and prepare his house for an estate sale.

When I was cleaning his office, I found a strange note.  I’ve stared at it for hours, and I just can’t figure out what it means. Maybe you can help. I am attaching a copy at actual size. I added a 1″ mark on the side, so if you print it, you can make sure it’s properly sized.

The note wasn’t the only strange thing in his office. Every square inch was filled with Coca Cola memorabilia — posters, newspaper ads, toys, and unopened bottles.  By far his largest collection was of 12 oz. Coke cans from different eras. There must have been hundreds!  And apparently when he wrote the note, he was thirsty. Right beside it was a Coke can, the only empty one in the room.

Other than the Coke memorabilia, the room looked like a typical office. On his desk were pencils, a spiral notebook, a cloth tape measure, Scotch tape, and a pair of scissors, though I doubt most of this has anything to do with the note.

Maybe it’s all just gibberish, or maybe there’s more than meets the eye. Can you help me solve the mystery?

With CodeAWeek.com, I hope to release one cipher, puzzle, or mystery every week. Anyone can attempt to solve. The winner is the first person to send a correct solution and a description of the solve method to codemaster@codeaweek.com. Once a correct solution is e-mailed, I will publish a follow-up post, congratulating the winner and revealing the secrets of the code.

You may post questions or theories in the comments, but DO NOT POST SOLUTIONS. E-mail them to codemaster@codeaweek.com.