Cryptography is the practice of encoding and decoding information so that only authorized people can read and understand it. Scrambling information to make it unreadable to those without the proper authority is called encryption and unscrambling it back to its original form is decrypting. A cipher is an algorithm for performing an encryption or decryption. Humans have always felt the need for security which can be as simple as locking the door to a house, or as complicated as creating biometric scanners. Locking sensitive data such as banking information or intellectual property from unauthorized access is a chief concern of information security analysts. In the age of the internet where sensitive information is constantly being transmitted, cybersecurity is an important and ever-growing field with many career opportunities.
Learn all about different techniques used to keep information secret!
The Goal: In this activity you’ll create your own substitution cipher to encode and decode secret messages just like Julius Caesar did over two thousand years ago!
Materials needed:
Pencil
Colored pencil, marker or pen (any color will do)
Scissors
Brass fastener or bent paperclip
Getting Started: In a substitution cipher, each letter of the plaintext (plaintext is the message which has to be encrypted), is substituted by another letter to form the ciphertext (the ciphertext is the encrypted message). For example, you might shift each letter by 3 places, so that the letter “A” is replaced by “D,” the letter “B” is replaced by “E” and so on. The letters would wrap around at the end so “X” would be replaced by “A.”
Instructions: First cut out the two cipher wheel circles. On the larger wheel, write the letters A-Z in the outer squares and the numbers 1-26 on the inner circle squares. These will be the plaintext characters. On the smaller wheel, in a different color write the letters A-Z again. Using a different color can help when distinguishing plaintext and ciphertext. The letters on the inner wheel will be the ciphertext characters. Next, affix the smaller circle onto the bigger circle using a brass fastener or bent paperclip through the center.
Now it’s time to practice. To encode and decode a message, the sender and the recipient must both know the position shift, or what to “set” the wheel at. In this example, the wheel is set for a shift of 19 so that “A” becomes “T.” See if you can decode this ciphertext: VHWX BL VHHE. (Look at the letter on the inner circle to see the corresponding letter on the outer circle.)
Click here to see the answer!
Plaintext: Code is Cool
Once you’ve gotten the hang of it, you can create your own messages. You could even use it to create secure passwords (just don’t forget the wheel setting!). Think about these questions: How easy is it for someone who intercepts a secret message written using this cipher to work out the original message? Is there any way to make it harder to figure out? What other methods of encryption are you familiar with or do you have ideas for new encryption methods? One of the most famous encryption devices is called the Enigma machine. Used by Nazi Germany during WWII, it took the Allied forces years to figure out how to break the code which ultimately helped win the war and saved countless lives.
More to explore!
Computers fill a crucial role in the function of our society, so check out this series to gain a better understanding of how far computers have taken us and how far they may carry us into the future.
Can you crack the code? Learn simple techniques for breaking (or cracking) codes with this online introduction to Simple Encryption:
Learn more about and explore different types of ciphers:
Watch this video about The Caesar Cipher: