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.