Secret Codes - Activity Pages

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NATO Phonetic Alphabet
This code replaces each letter with a word that begins with that letter.
The replacement words are easy to tell apart from one another when
spoken. This is a spoken code and is good for two-way radio
communication, when static often makes it difficult to tell two similar
sounding letters, like B and D, apart
Alpha
Bravo
Charlie
Delta
Echo
Foxtrot
Golf
Hotel
India
Juliett
Kilo
Lima
Mike
November
Oscar
Papa
Quebec
Romeo
Sierra
Tango
Uniform
Victor
Whiskey
X-ray
Yankee
Zulu
Say out loud the following letters: B C D E P T V Z
Now say out loud the NATO Phonetic Alphabet code words for each of
those same letters
Is it easier to hear differences between the letters or the code
words?
Make a short phrase and write it down below. Find a partner. Tell
your partner the NATO Phonetic Alphabet code for your phrase and
see if he or she can figure out what you said.
Switch places and see if you can figure out your partner’s phrase.
Caesar Ciphers
In a Caesar cipher, the alphabet is shifted and each letter in the message is
replaced by the corresponding shifted letter.
For example, shifting the alphabet 3 spaces to the left changes a to D, b to E, c
to F, and so on.
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
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
Using this cipher, the phrase cub scout becomes FXE VFRXW.
To change a Caesar cipher quickly, you can use a cipher wheel.
Encrypt this sentence.
Key: Caesar cipher with a left shift of 3
Plaintext:
keep this a secret
Cipertext:
____ ____ _ ______
Decrypt the answer to the riddle.
Key: Caesar cipher with a left shift of 3
Riddle: What do you call a sleeping bull?
Cipertext:
D EXOOGRCHU
Plaintext:
_ _________
Decrypt the answer to the riddle.
Key: Caesar cipher with a left shift of 4
Riddle: What do you call a dog at the beach?
Cipertext:
E LSX HSK
Plaintext:
_ ___ ___
Break the code by figuring out the key. (Let the one-letter words help you.)
Then decrypt the answer to the riddle.
Riddle: What’s the noisiest dessert?
Ciphertext:
W GQFSOA
Plaintext:
_ ______
Key: Caesar cipher with a ______ shift of ____.
Break the code by figuring out the key. (Let the one-letter words and two-letter
words help you.)
Then decrypt the quotation by Albert Einstein.
HS RSX ASVVC EFSYX CSYV HMJJMGYPXMIW MR QEXLIQEXMGW,
M EWWYVI CSY XLEX QMRI EVI KVIEXIV
Key: Caesar cipher with a ______ shift of ____.
Challenge: Every shift to the left by some number of spaces is the same as a
shift to the right by some (possibly different) number of spaces. How are the
two shift numbers related to each other? How do you know?
Some activities drawn from The Cryptoclub: Using Mathematics to Make and Break Secret Codes by Janet
Beissinger and Vera Pless.
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