Atbash Cipher Lesson Plan

Lesson Duration:

45 - 80 minutes

Lesson Objectives:

Understand what the Atbash cipher is and its historical context.
Learn how to encode and decode messages using the Atbash cipher.
Implement the cipher using manual and programming techniques.

Materials Needed:

Whiteboard or chalkboard

Lesson Breakdown

1. Introduction to the Atbash Cipher (20 minutes)

Discussion Questions:

Key Concept: The Atbash cipher is a simple substitution cipher where letters are replaced with their reverse alphabet counterpart.

2. How the Atbash Cipher Works (15 minutes)

Letter mapping:

Plaintext	A	B	C	D	E	F	G	H	I	J	K	L	M
Ciphertext	Z	Y	X	W	V	U	T	S	R	Q	P	O	N
Plaintext	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
Ciphertext	M	L	K	J	I	H	G	F	E	D	C	B	A

Exercise: Have students encode their names using the Atbash cipher.

3. Decoding Messages (10 minutes)

Provide students with a message written in Atbash and ask them to decode it.

GSRH RH Z HVXIVG (This is a secret)

Mr. Cusack will give you two message to encode and decode.

4. Handling Numbers and any non alphabetic charaters in the Atbash Cipher

Leave Numbers any non alphabetic character Unchanged

The simplest approach is to ignore numbers and only apply Atbash to letters.
Example:

Input: "HELLO123"
Atbash Output: "SVOOL123"

5. Wrap-Up & Reflection (5 minutes)

How does the Atbash cipher compare to modern encryption methods?
Why is Atbash not secure for modern use?
Where might simple ciphers like this still be useful?

Assessment

Go to the Board.
Encode a message Mr. Cusack gives your team into a AtBash message.
Decode an Atbash message Mr. Cusack gives your team into plain message.
Get Mr. Cusack's signature.
Take a picture and upload it to your google docs.
Students submit the screen print of their Notes to google classroom.
The file name will be PX_lastname_AtbashCipherNote.png

Lesson Summary: Students will learn the Atbash cipher, practice encoding and decoding messages, and optionally implement it in code.