# BLOSSOMS Cryptography Lesson Adapted for “Strong Women, Strong Girls’ Jump into Spring” Event

April 19, 2014

Guest Contributor: Amy Beth Prager

I recently had the pleasure of hosting a Cryptography Exhibition at the Strong Women, Strong Girls’ Jump into Spring event, representing the Cambridge Science Club for Girls. Strong Women, Strong Girls is a nationally recognized multi-generational mentoring program. This even drew hundreds of elementary school girls from the Boston area to a convention center where numerous social service agencies gave ongoing presentations designed to educate and inspire the girls, who moved freely around the exhibition hall.

As a guide for this Cryptography Exhibition, I used the MIT BLOSSOMS lesson, “Building Cryptosystems”. In order to better suit the large and younger audience, I used a whiteboard to present the concepts of cryptography presented in the BLOSSOMS video, rather using physical props. We went over the principles of coding using a shifted alphabet, a randomized alphabet, and multiple randomized alphabets. In addition, my co-presenter and I introduced a new feature to the lesson plan - we had the girls construct their own code!

We began our presentation by teaching the basics of cryptography. We asked the girls “How would you send the message ‘HELLO’ to your friend such that no one else could read it?” The girls experimented with assigning numbers or letters to each letter in order, but soon realized that this would be quite easy to break. We then used codes with numbers or letters in random order to represent the letters. We also discussed having a different key for each letter in the word ‘HELLO’, thus increasing the security of the message.

After grasping the idea of a cryptosystem and some possible ways to construct them, it was time for the girls to construct their own code! We were extremely impressed with what the girls came up with, as it was something so original and unusual that I myself had never thought of it before!

The code the girls came up with consisted of the first 18 letters of the alphabet put into a 3x3 grid, two letters to a box. The remaining eight letters were put into an “X” shape, two letters to a wedge. The code thus became the enclosure of the letter, with a dot in the middle to signify the second letter in the box or wedge. For example, _| would signify the letter ‘a’.

I was very impressed by the creative thinking and understanding that led to this coding scheme. It was a beautiful experience delivering this BLOSSOMS lesson to a younger audience and watching it unfold. I greatly look forward to implementing more lessons from MIT BLOSSOMS and working with other groups of girls in an informal educational setting!

Amy Beth Prager

The code we developed:

ab  |  cd  |  ef

____|_____}____

|         |

gh  |  ij     |  kl

____|______|_____

|          |

mn | op    |  qr

\          /

\ st  /

uv    /  \ wx

/ yz     \

(The above should be an X shape but I could not format it using word.)

The code is the enclosure of the letter, with a dot in the middle to represent the second letter of the pair. For example, ___| represents a , and |__ represents c.