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Vigenere Cipher [GRAVITY FALLS SECOND SEASON]: Code Cracking 101


Welcome to another episode of Code Cracking
101, the series that teaches you the basics of deciphering the codes found in the hit
Disney TV show, Gravity Falls. I’m your host, Douglas MacKrell. The second season has finally begun, and with
it, an entirely new way of encoding secret messages. It seems like all of the old methods
are still in play – Caesar, Atbash, and even A1Z26 – but in the episode Scary-oke, Alex
and his team utilize a brand new style of encoding. So in this episode I’ll be jumping
ahead sharing the secrets of the Vigenère Cipher! Much like the Northwest Family’s shady past
with the US Government, the story of the Vigenère Cipher begins with a cover-up and ends with
an altered history. In 1508, Johannes Trithemius created a brand new way of encoding messages
based off a constantly shifting cipher. To decode and encode messages, he also invented
the tabula recta – a square tool of shifting alphabets. The problem with Trithemius’ Cipher is that
it relied on a very predictable shift pattern and as such it was still very easy to crack.
But in 1553 Giovan Battista Bellaso published a book that detailed the use of the tabula
recta in conjunction with a password or passphrase that made the code nearly unbreakable at the
time. The problem was that this was not a very popular
book, and Bellaso’s work went mostly unnoticed for many years, until suddenly in 1586 – barely
thirty years later – French Diplomat and well regarded rich guy, Blaise de Vigenère, presented
basically the exact same cipher that Bellaso invented to the court of King Henry the third
of France as the “autokey cipher”. Vigenère’s possible theft became a smash
success, and history attributed the cipher to his name. Even the tabula recta is known
in most circles as the Vigenère Square. If it had not been for the work of some dedicated
historians and archivists, Bellaso’s work would have never been discovered and history
would remember Vigenère as the true inventor. As for how it works, the Vigenère Cipher
is one of the first polyalphabetic ciphers ever used. Until now in Code Cracking 101
we’ve only used monoalphabetic ciphers. The easiest way to explain the difference
between a monoalphabetic cipher and a polyalphabetic cipher is by using one of the Royal Order
of the Holy Mackerel Decoder Disks I’ve created. As I’ve explained before, to use one of
these decoder disks, you use the key I provide to lock the disk to a specific letter so you
can decode the whole message. You see, after you lock it in, a single alphabet decodes
the entire message. Hence “monoalphabetic” or “one alphabet”. A polyalphabetic cipher shifts the disk after
every letter of the encoded message, essentially creating a new alphabet to decode each letter.
Hence “polyalphabetic” or “many alphabets”. And that brings us back to the Tabula Recta,
which I’ll call the Northwest Square – because I feel that basically sums up this whole Vigenère
conspiracy, and I hate saying “Vigenère”. For everyone’s convenience, I’ve created
a Northwest Square for you to download, print, and learn from. You can find a link to download
one in the About Section below this video. So before we get to our first example, let
me explain how to use a Northwest Square! First, you’ll need to know or discover the
password or passphrase. After writing your encoded message down, write the password directly
above the message, repeating the password if it’s shorter than the encoded message. On the left hand side of the square, is the
encoded alphabet. Every letter of the password will match up with the letters lining the
outer left side of the square. With your password set, find the row with
the first letter of the password and then scan that row to the left until you find the
letter of the encoded message. Next, you scan up the column of the encoded message letter
to the top line of the Northwest Square! That’s your decoded letter! In the second season so far, Alex has shown
that he won’t be overtly telling us what the key word is, it will be hidden somewhere
in the actual episode. In the case of Scary-oke, the password was carved into the wall of Gideon
Gleeful’s cell next to a picture of a key. So as you can see, the password for this episode’s
secret message is “Widdle”. Now that we have our password, let’s look
at Scary-oke’s encoded message. Like before, we first write out our password “widdle”
above the encoded message letter for letter – making sure to start the password again
when we reach the encoded letter A. With that in place, let’s decode this message!
We start with the letter W which matches with the password letter S in that same row. We
slide up the column, and reveal that the first decoded letter is W! Congratulations! you’ve
just decoded your first letter with a Vigenère Cipher! Let’s continue. I matches with M and decodes to E. D matches
with O and decodes to L. D matches with F and decodes to C. L matches with Z and decodes
to O. E matches with Q and decodes to M. W matches with A and decodes to E. That makes
our first word, “Welcome”! Now let’s decode the final four letters.
I matches with J and decodes to B. D matches with D and decodes to A. D matches with F
and decodes to C. And finally, L matches with V and decodes to K. That completes our final
word and reveals the secret message, “Welcome Back”! As you can see, once you discover the password
– decoding a message encoded with the Vigenère Cipher is a breeze. So keep your eyes peeled
for keys and passwords in the upcoming episodes, because without them – all of the Northwest
Squares in the world won’t help you decode the secret message! Speaking of which, remember to follow the
link in the about section below this video to download and print your own copy of my
Northwest Square. That way you can tackle the secret messages of the upcoming episodes
on your own! If you have any questions or if you’re still confused by the process
– be sure to sound off in the comments below, and I’ll do my best to answer your questions.
Until next time, share, subscribe, and keep cracking those codes! The message on the blackboard is your homework
assignment. A secret message encoded with the Vigenère Cipher. Use your newly printed
Northwest Squares to decode the message! Remember: repeat the password “Mackerel” letter
for letter over the encoded text so you know how to read your Northwest Square!

67 thoughts on “Vigenere Cipher [GRAVITY FALLS SECOND SEASON]: Code Cracking 101

  1. This is really one of your awesone episodes :D. And another thing your voice is majestic dude…………..lol

  2. first,, are they nutz? with out someone like you how do they expect kids to decrepit this? also how do they expect most kids to listen to the back words talking in the opening credit's too?
    second, is that wheel even necessary now that we have this chart? couldn't it be used in the same way as the wheel? all you have to do is highlight the aporpreit line of latters and fallow the line up to the top row.

  3. Can you talk about mable in the next episode because I think mable knows about the books because in the mailbox mini episode when dipper was just about to ask it who wrote the books mable comes in and she might of know the gummy worm video is stupid enough to explode the mailbox so can you please add this.

  4. At first I was like 😰 WHAT ARE YOU TALKIN ABOUT?!?!?! now I'm like 😂 thank you I wanna hug you for helping me understand.

  5. A sufficiently long Vigenere message can be cracked without knowing the key. There is a method called "Kasiski examination" that looks for repeated patterns of letters, which might be repeated letter pairs in the message encoded with the same parts of the key. The spacing between them is a multiple of the key length. Once you know the key length, the key letters are easy to find by frequency analysis. I wrote a computer program to crack Vigenere ciphers in college.

    However, very short messages like "Welcome back" cannot be cracked this way.

  6. I looked around your channel but haven't found anything. Have you analyzed the "Fixing it with Soos" shorts, specifically the image Soos draws on the back of the mystery cart? The one with the tiger, space ship, lake with an eye and gold pyramid?

  7. did anyone see the Mexican place in  the golf war is called hermanos brothers witch means in spanish  pollos hermanos witch is the BRAKING BAD  Mexican restraint 

  8. If any of you have decoded the first episode's credits code, you will see "Welcome to Gravity Falls" and we now know in the first episode of the second season it says "Welcome back". Am I the only one that noticed?

  9. If the Square is too much of a hassle, I found a very simple decoder site that open for free use: http://www.cs.du.edu/~snarayan/crypt/vigenere.html I used it to double check my hand decoding for this message, and it showed me that I had screwed up on several letters. Happy decoding!

  10. Well done. I like hearing your theories, but it's cool to see the change of pace and hear you talk a bit about the history behind the development of the ciphers as well as how to crack them. Nice. 😀

  11. So, I still don't understand how to use the disk for the polyalphabetic cipher, can you please explain it?

  12. AH HAAA I see it there is even a secret message in the weel thinggy you made it seas "stanford" as in stanford the author of the Journal in gravity falls 03:37 < thays were it is!

  13. Thank you for doing this. I was so confused by the Vigenere Cipher wondering how anyone was actually using it. Now I understand so maybe next time I can try it myself.

  14. i just noticed this.. Caesar Cipher, Batast Cipher, Veginere Cipher, Bill Cipher… A-X-O-L-O-T-L MY TIME HAS COME TO BURN I INVOKE THE ANCIENT POWER THAT I MAY RETURN!!!! IN THIS UNIVERSE!!!!!!

  15. Actually, it is possible to break Vigenère's cipher without having the key ;> Since the password is being repeated over and over, you periodically reuse the same sequence of alphabets. Think of it as a sequence of Caesar's ciphers with different shifts. If you know (or can guess) the length of the key, you can break the text into lines of the same length as the key, and then every column will use the same alphabet for encryption :> So you can use the same letter frequency techniques you used for breaking Caesar's cipher for breaking each column. And with each column, you crack one letter of the password too ;> So if you can fill in the gaps in the password, you've already solved it :> (This is actually how I cracked those codes for several episodes, without knowing the key, because I couldn't find it at first.)

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