Students learn about the Caesar Cipher and the Vigene ̀re cipher. They practice encoding and decoding messages using a decoder ring.
First I opened the decoder ring found here http://www.thingiverse.com/thing:14891 in TinkerCad. Then I added a rectangular prism and put a hole in the center so that the letters would be visible. Then I made the ring a hole and cut it away from the box [figure 1]. Next I cut out the middle parts, leaving a little part going up on the bottom so to hold the part in place [figures 2 & 3].
Project: Cryptography: Sending Secret Messages
Students get an introduction to cryptography. They learn two ciphers and practice encoding and decoding messages using a decoder ring that is 3D printed.
Students will learn what cryptography is and get some practice sending and receiving messages.
Students learn the Caesar Cipher and the Vigene ̀re cipher and how to use them.
CCSS.Math.Practice.MP1 Make sense of problems and persevere in solving them.
CCSS.Math.Practice.MP5 Use appropriate tools strategically.
Students are introduced to the Caesar Cipher and then they practice decoding a message. They think of why this cipher doesn’t work well. Then they learn the Vigene ̀re cipher and practice decoding a message. Students then figure out how to use the decoder ring with the Vigene ̀re cipher. Finally, they encode a message and trade with another group to decode their message. As an optional extension, students figure out how these ciphers relate to modular arithmetic.
This activity should take one day.
No background is needed for this activity. For the extension students should know modular arithmetic.
Here is a sample rubric to use with the worksheet.