Solution - Indecipherable

by Harley Zhang

Answer: Click here to reveal

Each of the doors contains a block of encoded text, which have been encrypted using Vigenère ciphers with different keys. The usage of this cipher is clued by the title of the puzzle, as the Vigenère cipher was once known as the "indecipherable cipher". In addition, the distributions of letter frequencies do not match normal English text, so the encryption method likely does not use a substitution cipher.

The ciphers can each be broken by first detecting repeated substrings to guess a key length (n). The key length matches the number of line segments in the image below the text. The Vigenère cipher can then be broken up into n instances of a Caesar cipher, which can then be broken through a combination of letter frequency analysis and logic, since the recombined text should spell out a message. One commonality that emerges from the eight Vigenère cipher keys is that they only use the letters A through G, which further facilitates breaking the ciphers.

Each cipher key represents a sequence of musical notes (with no sharps or flats unless explicitly indicated) from a song, which must be identified. All of the songs are covers by Alvin and the Chipmunks and/or the Chipettes, as indicated by the flavor text. The image below each text block represents the relative note lengths and octaves. Each individual line segment represents one note. The length of the line segment is proportional to note length, and the octave of the note is indicated by the vertical position of the line segment, with octaves starting from the first degree of the key and higher vertical positions indicating a higher octave. Accidentals outside of the key are explicitly marked. The decoded text contains clues to the titles, artists, or lyrics of the corresponding songs, among a lot of other junk text. The given enumerations match the song titles.

Note (no pun intended) that the music note sequences in the cipher keys are presented in various different musical keys; the letter of each musical key must be identified. The capitalization of the encoded text provides a clue to the musical key: all-uppercase text corresponds to major (M) keys, and all-lowercase text corresponds to minor (m) keys.

With the "key" determined, the "lock" to each door must be identified. In each decoded text block, there is one word to which the word "lock" can be appended to form another reasonably common word (e.g. "grid" + "lock" = "gridlock"); let's call this the lock-word. The number of letters in the lock-word is indicated by the number of blanks preceding “lock“ for each door. For each door, the lock-word contains the letter of the door's corresponding musical key in exactly one position. Indexing this position into the corresponding song title provides the extraction of one letter per door. When read in the original numerical order of the doors, these letters spell the final answer: PIANO TAB. Decrypted text for each door follows below.


Door 1:

Decoded text (with punctuation added):

Do not try to go through this door. King Kong is sleeping behind this door. You could try to slip in silently like a sneaky spy to not wake him up, but it is very dark and you have no flint or tinder with which to make a fire, so you will have trouble seeing where you are going. If you bump into something and make a loud noise, he will wake up and be very angry. He has great night vision, and he will pursue you in circles around the chair he sits on when he is making shoes. He is very fast, and he will not hesitate to rip you apart limb from limb, or at least take all of your copper coins to fund his sewing addiction. He is really not a very nice guy, which is why we keep him locked behind this door.

Cipher key: CFFGGACAFCFFGGAF

Song: Pop Goes the Weasel (clues in text: King Kong = monkey; sneaky spy = weasel; pursue you in circles around the chair he sits on when he is making shoes = ‘round and ‘round the cobbler’s bench the monkey chased the weasel; copper coins to fund his sewing addiction = a penny for a spool of thread, a penny for a needle)

Musical key: F major

Lock-word: flint

Index of musical key into lock-word: 1

Extracted letter from song title: P

Door 2:

Decoded text (with punctuation added):

Pay no attention to this door. It is definitely only a figment of your imagination. Shouldn't you be doing something else right now? Maybe go take a nap; you must be very tired. Doesn't a warm, soft bed sound lovely right now. You're probably also hungry right now too. Is that your stomach growling? You should go eat something. Go order some takeout, maybe some sushi or pad thai; doesn't that sound delicious? If it's nighttime and you have been inside all day long, go take a walk outside. Look up and reflect on what you see and your place in the cosmos. You might be able to find the answers to some deep questions, certainly more important ones than what is behind this non-existent door.

Cipher key: DDAABBA

Song: Twinkle Twinkle Little Star (clues in text: "look up and reflect on what you see" = "how I wonder what you are"; cosmos)

Musical key: D major

Lock-word: pad

Index of musical key into lock-word: 3

Extracted letter from song title: I

Door 3:

Decoded text (with punctuation added):

Don't open this door. It only leads to sorrow and heartbreak. The path forward has been followed by so many unhappy couples. People like Antony and Cleopatra and Romeo and Juliet have gone through this door, who loved each other but were forced apart by circumstances outside of their control. Other people have gone through this door who maybe should never have been together in the first place, like Mae West, who had denied that she had been wed to her first husband. Maybe some people were just never meant to be. Only rarely will a couple find each other and stick together forever. It takes so much luck and perseverance to find love and keep it. When love goes sour, there is no way to turn around and go back on this path. Once this door has been opened, it cannot be closed again. Are you still sure you want to open this door? You probably will not like what you find there, and you will probably regret going through.

Cipher key: EEBBCBEEBBCBGGEGG

Song: Bad Romance, by Lady Gaga (clues in text: unhappy couples, love goes sour = “bad romance”)

Musical key: E minor

Lock-word: wed

Index of musical key into lock-word: 2

Extracted letter from song title: A

Door 4:

Decoded text (with punctuation added):

The first steps you take past this threshold will seem to be fine. Nothing will seem to be wrong initially, but in your head, distrust will start to grow, slowly at first, but it will soon become overpowering. The friends you have with you will become your enemies, and there will be bloody fighting among you and these former friends. One by one, you will fall at each others' hands as the irrational fear and rage course through each one of you. If you are fortunate, maybe you will be the one who survives and walks out and back to where you came from. Or if you are one of the unfortunate ones, then this will be the end.

Cipher key: AADDDEFEFDCAC

Song: When Johnny Comes Marching Home (clues in text: bloody fighting among former friends = Civil War; one who survives and walks out and back to where you came from = “comes marching home”)

Musical key: D minor

Lock-word: head

Index of musical key into lock-word: 4

Extracted letter from song title: N

Door 5:

Decoded text (with punctuation added):

Let me tell you what you will see beyond this door. There is nothing too bad, mainly just small annoyances: things like the sound of a fly constantly in your ear, erratic flickering lights, water droplets falling and bursting into flame, a bad smell that you can't exactly identify, the feeling of small claws tugging at the hem of your pants. Individually, these would not be too bothersome and surely one would be able to survive this, but put this all together and another story may unfold. You will end up going in circles, forced to walk the same path endlessly over and over again. Eventually, you will not even know whether you are still living and breathing, or if you have passed away and are dreaming an endless repetitive nightmare. If you think you are strong enough to survive this ordeal, pass through. Otherwise, stay out.

Cipher key: EEEGGDDAGEEEAAGG

Song: You Spin Me Round, by Dead or Alive (clues in text: “going in circles, forced to walk the same path endlessly” = “spin me round”, “whether you are living and breathing, or if you have passed away” = Dead or Alive)

Musical key: E minor

Lock-word: hem

Index of musical key into lock-word: 2

Extracted letter from song title: O

Door 6:

Decoded text (with punctuation added):

Why should I bother trying to keep you out? I’m feeling so blue, I don’t have the energy to try to convince you to keep this door closed. All of this is so pointless. There’s no point in fighting a war between us. I can’t even throw a punch right now. Just hurry up and open this door already, I won’t stop you. What are you waiting for? I told you I won’t stand in your way. Hurry up before I change my mind.

Cipher key: EAACEACEDCA

Song: It Don’t Mean a Thing (If It Ain’t Got That Swing), by Duke Ellington (clues in text: pointless = “don’t mean a thing”; can’t even throw a punch = “ain’t got that swing”, blue -> blues/jazz)

Musical key: A minor

Lock-word: war

Index of musical key into lock-word: 2

Extracted letter from song title: T

Door 7:

Decoded text (with punctuation added):

Congratulations on getting this far. You have done well to persevere this far unharmed and completely intact. This is a very impressive feat. However, it remains to be seen whether you will continue to survive. I cannot tell you anything about what lies behind this door, except that there are many things that could harm you behind this door and many ways that you could wind up dead. You have shown yourself to be skilled already, so you should be able to pass through this door without perishing, even with no knowledge of what lies beyond. But you have also had some luck on your side. Be grateful, brave and gallant boys and girls.

Cipher key: EDCBBCCCBCCC

Song: Stayin’ Alive, by the Bee Gees (clues in text: continue to survive = “stayin’ alive”; last sentence contains words starting with letters alternating between “B” and “G”)

Musical key: A minor

Lock-word: dead

Index of musical key into lock-word: 3

Extracted letter from song title: A

Door 8:

Decoded text (with punctuation added):

Well, here is the last door. You have gone through a lot to get here. Thinking back, it seems like nothing has gone right for you today. The path to this point has been difficult and it is not quite finished yet. If that makes you feel really sad, you can belt out a musical lamentation of your woes to try to improve your day. If you make it through this door, taking a vacation to somewhere sunny with clear skies might help too. Go off the grid for a while, stop checking your email, relax a little bit. You deserve it, you should be very proud of yourself. Treat yourself to something nice. Maybe tomorrow will be better.

Cipher key: DDDBDAGGBDAGEDBCBBA

Song: Bad Day, by Daniel Powter (clues in text: nothing has gone right for you today = “bad day”; belt out a musical lamentation of your woes to try to improve your day = “sing a sad song just to turn it around”, a lyric from the song; vacation to somewhere with sunny skies = “blue sky holiday”, a lyric from the song)

Musical key: G major

Lock-word: grid

Index of musical key into lock-word: 1

Extracted letter from song title: B