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Lesson 3 - Vigenère, Morse and Pig pens!

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Overview
Flight Path
Learning Objectives
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 2 I can identify reasons that secret societies use ciphers.
 4 I can create and solve Morse code with a machine.
 6 I can evaluate the importance of further development of strong ciphers such as the Vigenère.

🏁 Learning Objective 9 :- I can identify reasons that secret societies use ciphers.


Task - Find out what a pigpen cipher is, who used it and then see if you can write your name in it?

Pigpen

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🏁 Learning Objective 10 :- I can create and solve Morse code with a machine.


Morse code

Morse code was invented by Samuel Morse in 1832. Letters and numbers are represented by a series of dots and dashes - a dash lasts three times longer than a dot.

Morse code is a digital signal. It can be transmitted in many different ways, including visible light, radio waves and electrical pulses.

Sending information using electrical pulses requires wires, unlike visible light and radio waves, which are wireless. The use of visible light needs the transmitter and receiver to be in the line of sight, but that is more secure against eavesdroppers than radio waves.

The Morse code

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🏁 Learning Objective 11 :- I can evaluate the importance of further development of strong ciphers such as the Vigenère.


Decrypting The Vigenère Cipher

Let the key be KEY. You wants to decrypt NGMNI.

  • locate the first letter of the key in the left column, and locates on the row the first letter of the ciphered message.
  • Then go up in the column to read the first letter, it is the corresponding plain letter.
  • Locate the letter K on the first column, and on the row of it, find the cell of the letter N, the name of its column is D, it is the first letter of the plain message.
  • Then continue with the next letters of the message and the next letters of the key, then at the end of the key, go back the the first key of the key.
Key K E Y K E
Encrypted Text N G M N I
Decrypted Message D C O D E

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

Decrypt the message ZMEZIL using the key 'KEY'

Click on the excel icon below to download the Excel activity sheet!



Extension task

  1. Decrypt the message K IB PR KJM XSPLOQCHXZ using the key 'CIPHER'

The Vigenère Cipher

The Vigenère cipher, was invented by a Frenchman, Blaise de Vigenère in the 16th century. It is a polyalphabetic cipher because it uses two or more cipher alphabets to encrypt the data. In other words, the letters in the Vigenère cipher are shifted by different amounts, normally done using a word or phrase as the encryption key .

Unlike the monoalphabetic ciphers, polyalphabetic ciphers are not susceptible to frequency analysis, as more than one letter in the plaintext can be represented by a single letter in the encryption.

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

The Vigenère cipher uses this table in conjunction with a key to encipher a message.

So, if we were to encode a message using the key COUNTON, we write it as many times as necessary above our message. To find the encryption, we take the letter from the intersection of the Key letter row, and the Plaintext letter column.

Key C O U N T O N C O U N T O N
Plaintext V I G E N E R E C I P H E R
Encryption X W A R G S E G Q C C A S E

Task

Encrypt the message 'To be or not to be' using the key 'KNOLE'


Extension task

  1. Create your own Key and encrypt the message 'To be or not to be' ?
  2. Create your own Key and encrypt your own message?

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Teacher Date: 2020-07-05


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