Lesson Plan: Chapter 7

Connecting to CSTA Standards

GradesConceptSubconceptStandard NumberPractice
6-8Networks & the InternetCybersecurity2-NI-06Developing and Using Abstractions: 4.4

Apply multiple methods of encryption to model the secure transmission of information.

Encryption can be as simple as letter substitution or as complicated as modern methods used to secure networks and the Internet. Students should encode and decode messages using a variety of encryption methods, and they should understand the different levels of complexity used to hide or secure information. For example, students could secure messages using methods such as Caesar cyphers or steganography (i.e., hiding messages inside a picture or other data). They can also model more complicated methods, such as public key encryption, through unplugged activities.

Learning Outcomes/Goals

One of the most entertaining aspects of childhood - sending secret messages - is explored in this chapter, in depth, from a technical standpoint. While the storyline is all about a secret language that ants use to transmit messages about locations of the special moss that they curate, secret codes and the need to encrypt and decrypt them securely has been a pertinent topic since ancient days. Learning about the various ways that messages can be encrypted and decrypted, following the metaphor of the ants' secret codes, will allow students to better understand how secrets are kept safe from prying eyes on the internet.

Students will learn about cryptography, in particular the use of the two most basic types of encryption, the Caesar cipher and the Vigenère cipher. Other ciphers are studied as well, and students learn about the need for keys to help decrypt the messages. By using various ways to try to decrypt the ants' secret message, first using a brute force technique of educated guesses, then trying frequency analysis.

Differentiated Instruction

Lower level studentsHigher level students
Students should be able to understand the basics of the Caesar and Vigenère ciphers and how to crack them, perhaps using Cryptii.com as a tool to decipher them.Students can study more challenging methods of cryptography, exploring modern methods and how they apply to the current state of the art.

Transfer Learning

Students can turn to history to explore how various messages have been encrypted and decrypted. The famous 'code crackers' of Bletchley Park, where Alan Turing worked during WWII, are celebrated at the National Museum of Computing's web siteopen in new window. Learn how Julius Caesar, Giovan Battista Bellaso (the Vigenère cipher was his invention, and it was misattributed to Blaise de Vigenère in the 19th century), and others created their ciphers, and how they were cracked later. Is there such a things as an indecipherable ciper in today's world?


  • Cryptography: From the Greek words for the study of secret writing, cryptography is the study of how to encrypt and decrypt secret messages by using various techniques spanning the realms of information technology and computer science.
  • Encryption: The process of encoding messages from plaintext to 'ciphertext', its encrypted version.
  • Steganography: A technique whereby a message can be cconcealed in another message, image, or other object


Students should be able to describe a given cipher and show how it can be deciphered by the use of keys. They should understand the difference between public and private keys and how they work together.

Research a cipher and write an essay of its use, its history, and how it can be deciphered, paying attention to its historical context and how it drew on prior history of cryptography.Write a summary of how a given cipher can be cracked by use of various tools such as public or private keys

Quiz Answers

Steganography allows you to hide a message in an audio or image file.

a. True

b. False

Symmetric encryption is a method of encrypting data using:

a. A public key

b. An NFT

c. A shared secret key

Asymmetric encryption is a method of encrypting data using:

a. Two keys

b. One private key

c. One shared key

More Resources/Materials

Solution Code

The decoded ants' message is "The moss is in the cave at 42.361145 latitude and -–71.057083 longitude" and the shift is 4+. You can check this using a Caesar cipher with a shift of 4+ on Cryptii.com.

Assignment and Rubric: Let's Encrypt

In this chapter, you learned about different methods of encryption used to protect data. Practice your knowledge by converting a message using an encryption technique of your choice, and challenging others to decipher it. Research and try:

  • A Caesar cipher

  • A Vigenère cipher

  • An encryption technique of your choice

ExemplaryAdequateNeeds Improvement
The student creates an encrypted message and partners with a peer to try to decrypt it, noting the necessity of understanding the type of encryption used and the key needed, if brute force decryption proves fruitlessThe student only creates an encrypted message but can explain the encryption type they used and the key needed to decrypt itThe student simply creates the encrypted message.

*tip: prior to saving as a PDF, select the 'light' mode at the top using the 'sun' icon.