STEAM II: Cryptography Is a Challenging and Fun Unit

Below is a student-written article featured in the latest issue of The Tie, Saint Joseph Prep Boston's student newspaper.


by Megan Graf '25


STEAM Lab—In STEAM II, the sophomores just wrapped up their unit on Cryptography. Cryptography is the study and practice of protecting information through codes. In this unit, students learned all about different types of codes, how to break codes, how to write your own codes, how codes are useful, and how they have been used within the real world. 

Interview with Ms. Gipson (Head of the STEAM department and the STEAM II teacher) 

The TIE: Why do you teach cryptography?

Ms. Gipson: I teach cryptography for multiple reasons including to disguise math in a way that students enjoy, instead of dread, to get students to turn to their peers for help instead of turning to me, and to teach and have students practice perseverance because cracking the code is not always easy, and sometimes it seems much easier to give up than to keep working to crack the code. 

The TIE: How do students normally react at the beginning vs the end of the unit?: 

Ms. Gipston: In the beginning, students are generally resistant or not as enthusiastic but towards the end of the unit, almost all of the students are wanting to immediately jump into breaking the codes as soon as they are presented with them, because they learn to enjoy the challenge of solving these codes. 

The simplest type of code we learned to solve is called a Caesar Cipher in which you are given a string of twenty-six cipher letters or encoded symbols, and then within that string, one of those letters/symbols will equal the letter A in normal text. From there, the normal text alphabet is set in chronological order to the cipher text, so you go through from letter A and fill in the rest of the letters until you reach the end of the string and then keep going at the beginning again. Or you could start from any other letter and still go chronologically. Finally, each cipher is going to have a different letter substitution, and therefore the messages will be different even if they use the same symbols or letters because they have different substitutions. 

For instance:  

Normal Text: A  B  C  D  E  F  G  H  I   J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

Cipher Text: E   F  G  H  I   J   K  L M N O  P   Q  R   S  T  U  V W X  Y  Z   A  B  C  D

Then based on the key you have filled in you can then figure out a code like:


If you want to try one all on your own here is one (#1): 

Normal Text: A  B  C  D  E  F  G  H  I   J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

Cipher Text:   A


(If the code makes sense then you did it right)

Sophomores also learned about random substitution ciphers, in which individual symbols correspond with each individual letter and there is no chronological way to solve the code. Because of this each symbol must be solved individually, and are harder to figure out. In order to start solving random substitution ciphers, the code needs to be evaluated and observed for frequency. Within a code, the lengths and frequency of letters and words within English are the only things that remain consistent in English and code, and therefore that is how you start solving the code. For instance, E is the most common letter in the alphabet, and “the” is the most common English word, therefore by looking for recurring symbols you can make assumptions about some common letters such as E. 

Secondly, the length of encoded words is one of the most helpful aspects of solving the code. Generally, you want to start at the shortest words and work upward. To elaborate, there are only two single letter words in the English language: I and A, meaning any single letter word must be one of those. Then you look for two and three-letter words and use the previously figured out letters to try and crack the shorter words. A tip for cracking these words is to first identify two or three-letter words and then plug in the letters that were already figured out. Once you plug in those letters you can try and figure out the words by thinking of common two/three-letter words such as “the”, “it”, “is”, “on”, “at”, “has”, “had” that contain the letters you figure out. Finally, you keep going to fill in the letters you have discovered and then guess the words based on the number of letters, context, and surrounding letters.  

You may try cracking this code #2:

Answer Key – Find out if your solution is correct!