Activity Handout: Build Your Own Cipher

Name: _____ Date: _____

This handout supports Cybersecurity Merit Badge requirement 6(c)(1).

You will create a simple substitution cipher and use it to encrypt and decrypt a message.

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Part 1 – Your Cipher Alphabet

Write the normal alphabet on the first line and your cipher alphabet on the second line. You may shuffle letters or create a pattern.

Normal alphabet:

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

Your cipher alphabet:

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(Each blank is the letter that will replace A, B, C, etc.)

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Part 2 – Encrypt a Message

Write a short, simple plaintext message (no personal information):

Plaintext message:

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Now use your cipher alphabet to convert it into ciphertext:

Ciphertext message:

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Part 3 – Decrypt a Message

Have another Scout (or your counselor) write a ciphertext message using your cipher alphabet. Write it here:

Ciphertext you received:

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Now decrypt it back to plaintext:

Plaintext you recovered:

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Part 4 – Strengths and Weaknesses

Answer in your own words.

1. One strength of your cipher:

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1. One weakness of your cipher:

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1. Why would modern attackers be able to break simple substitution ciphers quickly?

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Counselor Sign-Off Notes

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