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Cryptography Cryptography is derived from the Green word ‘kryptos’

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Presentation on theme: "Cryptography Cryptography is derived from the Green word ‘kryptos’"— Presentation transcript:

1 Cryptography Cryptography is derived from the Green word ‘kryptos’ which means hidden or secret

2 Cryptography Cryptography is thought to date back to the Egyptians and their use of hieroglyphics.

3 Cryptography Hieroglyphics were complex pictograms. At the time, the meaning of the hieroglyphics were known by only a few.

4 What does this hieroglyphic message say?
Cryptography What does this hieroglyphic message say?

5 Cryptography You can only understand this message if you have the code or the key to ‘unlock’ or decipher it.

6 Now you have the ‘key’, see if you can decipher the message.
Cryptography Now you have the ‘key’, see if you can decipher the message.

7 Julius Caesar developed the first modern cipher.
Cryptography Julius Caesar developed the first modern cipher. It is known as the ‘Caesar cipher’

8 Cryptography Each character in the message is replaced by the character three positions ahead of it in the alphabet

9 Cryptography A D B E G ? Z ?

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

11 Decode the following message: FURVV WKH ULYHU WRQLHKW
Cryptography A D B E C F G H I J K L M N O P Q R S T U V W X Y Z Decode the following message: FURVV WKH ULYHU WRQLHKW

12 CROSS THE RIVER TONIGHT
Cryptography A D B E C F G H I J K L M N O P Q R S T U V W X Y Z The message said: CROSS THE RIVER TONIGHT

13 Why might Julius Caesar encrypt his messages?
Cryptography Why might Julius Caesar encrypt his messages? Think of two disadvantages of using the Caesar Cypher

14 Cryptography Why might Julius Caesar encrypt messages his messages?
- So that he could safely send messages to his troops. Even if the messanger was caught, his enemies wouldn’t understand the message

15 Cryptography Think of two disadvantages of using the Caesar Cypher
-The person receiving the message would have to understand how to decrypt it Caesar ciphers are easy to break It doesn’t allow for numbers or symbols

16 Cryptography Plenary Explain the following terms to your partner: Cryptography Decrypt Caesar Cypher

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