How can you tell the difference between a good cryptography joke and a random string of words?

 Answer: You can't. They're indistinguishable.

Hello Codebreakers-in-Training!

Today we kicked off day 3 of our crypto-education with Transposition ciphers. Transposition ciphers are a catagory of ciphers that involve permuting (or shuffling) the characters in a message, instead of substituting them with new ones. This means that all of the letters originally in the message stay there, sounds easy right? That's what we thought too! We faced our biggest challenge yet, columnar transposition ciphers. 

Quote of the day: "This sounds like the easiest cipher yet." - Ella Perry

To begin encryption, we start with a familiar step 1: finding a keyword. Then, we take our plaintext message, and list it out from left to right, following the columns created under the keyword. We then take the letters of the keyword, and their corresponding columns, and rearrange them alphabetically. 

For example, 

   Keyword: LIST -> ILST

We then write out our ciphertext out from our columns. First completely writing out the first column from top to bottom, then the next column, and so on. And there you have it! A fully encoded ciphertext. To legitimately use this cipher, the receiver will attain a ciphertext and a keyword, they then will perform the above steps backwards.

 An example of a deciphered code.

A major problem to cracking this code is; without a keyword, we have no idea how big our grid of letters should be! Creating a difficult process of trial and error to work through. Although once we find our grid of letters, we can use the norms of the english language to figure out how our columns were shuffled.

An example of a code with a longer keylength.

After a much needed lunch break, we were back to solving codes. If the morning wasn't hard enough we mixed two codes together in the afternoon in a mixed cipher. The cipher was called the ADFGVX cipher because fittingly the cipher text only contains those characters.

You start by making a 6x6 key grid containing all characters of the alphabet and 0-9, and then substitute the characters in your plaintext for coordinates. (Each character in your plaintext will turn into two characters in the cipher text. Ex: A->FD)

An example key grid.

After we have found coordinates for each character, we apply the columnar transposition! This leads a ciphertext that contains only 6 different characters, with extremely high security. This code can only be reasonably broken under special circumstances: First, we must have a crib of some sort, and second, we must have a very good idea about what the size of the grid should be. Armed with these two things, we can reverse engineer this code using language norms.

 Our Cryptoanalysts battling with their first ADFGVX Cipher.

After a much needed break, we reconveened to enjoy pizza and watch a documentary on Elizebeth Smith Friedman. Detailing how one woman, Elizebeth Smith Friedman turned the tide in multiple wars, and against an onslaught of organized crime, using her exceptional cryptoanalyst skills. Her abilities created the foundations for where cryptology is today. Sadly, her work was not recognized until 2008, decades after she passed away. 

After a final discussion on what to pack for our trip to london, we bid farewell, until our next class tomorrow!

Good night cryptoanalysts!

-Rhodes Feild

-Ava Hershberg