Polybius was an ancient Greek who first figured out a way to substitute different two-digit numbers for each letter. In the Polybius cipher, we’ll use a 5×5 square grid with the columns and rows numbered. Take a look at the video and I’ll show you how it works.
Download Student Worksheet & Exercises
To make the Polybius more difficult to crack, you can write the alphabet backward or in an up and down pattern rather than left to right. Just be sure the decoder knows if you’ve used a different path or pattern to encode.
Exercises
- Write the grid that is used to encode and decode messages in the Polybius Cipher. (Can you think up your own?)
- Identify the codes representing the following letters using the grid from the example in the lesson: A, O and C.
Encode the following statements using the Polybius Cipher grid from the main lesson:
- LET US LEAVE
- I AM LEAVING
- THEY WILL COME
- SHE IS HERE
Decode the following messages using the Polybius Cipher grid from the main lesson.
- 32-35-35-31-11-45-45-23-15-45-11-12-32-15
- 24-45-24-44-23-24-14-14-15-34
- 23-15-43-15-24-44-45-23-15-41-11-41-15-43
- 32-35-35-31-11-45-33-55-12-35-35-31