Name: : : _____ Secret Codes Encryption is used by spies, secret

Name : _______________________________ Date : _______________ Period :

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Secret Codes

Encryption is used by spies, secret societies, and other organizations to transfer information without other people reading their messages. Secret codes can be created by a simple scheme of replacing letters with numbers. More complex codes replace letters with other letters. The code scheme is called a cipher and can be written as a list or table.

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

1 2 3 4 5 6 7 8 9 1

0

1

1

1

2

1

3

1

4

1

5

1

6

1

7

1

8

1

9

2

0

2

1

2

2

2

3

2

4

2

5

2

6

Use the cipher above to decode these messages.

Question ::

23 8 1 20 4 9 4 20 8 5 26 5 18 15 19 1 25 20 15 20 8 5 5 9 7 8 20?

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14 9 3 5 2 5 12 20

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Ciphers can be written in which letters are replaced with other letters, not numbers. A scheme is determined for replacement. Often, letters are shifted. For example, a letter could be replaced with the letter three down the 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

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

Using the cipher above , “

TWINKLE TWINKLE LITTLE STAR

” becomes “ WZLQOH WZLQOH OLWWOH VWDU

“.

The next line is

“HOW I WONDER WHAT YOU ARE”

Use the cipher to write it in code!

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A letter to letter code can also be represented in a graph. Determine the cipher represented in the graph below.

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

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

Use the code cipher above to code the message “

MATH IS FUN

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Use the cipher to decode “

T SLGP L DPNCPE

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