Students will use a substitution cipher to encrypt a message and then to decrypt a message. In a substitution cipher each letter of the alphabet is swapped with a different letter.
Substitution ciphers are significantly more secure than a Caesar cipher but require a more complicated key. Look at the differences in complexity and portability of different ciphers.
- Encode and decode messages using a substitution cipher.
- Identify the mathematical advantage of substitution over shift cipher.
- Print the Substitution Cipher Activity Worksheet
- Arduino Student Inventor Kit (Extended Activity)
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For the Teacher
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For the Students
Introduce the idea of a substitution cipher
- Each letter of our alphabet is swapped for that of a jumbled alphabet
- There are 26! different possible alphabets that could be used.
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Substitution Cipher Activity Worksheet
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Students will encrypt and decrypt several messages using a substitution cipher.
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They will then explore a keyword cipher and finally encrypt a message with a keyword to swap with someone else in the class.
- Python Programming: There are multiple ways to generate a "key" alphabet in the cipher.
- Python Programming: Program to analyze the letter frequency of a message.
- LetterFrequency.py
- Output of this is a CSV that can be graphed in Excel
- How is this type of cipher more secure than a shift cipher like Caesar?
- What are the weaknesses of this cipher?
- How does the random substitution compare to a keyword cipher?
- What are strengths/weaknesses of each?
- How would frequency analysis be used to decrypt a message encrypted with a substitution cipher?
- Is there are way to change this encryption so it is not vulnerable to frequency analysis?
Arduino Programming: Random Alphabet Generator https://circuits.io/circuits/5157643-arduino-alphabet-generator/
Cyber Security Curriculum 