Name : _______________________________ Date : _______________ Period :
_____
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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Answer :
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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