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Cryptography “The Secret Code Language”

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Presentation on theme: "Cryptography “The Secret Code Language”"— Presentation transcript:

1 Cryptography “The Secret Code Language”
Moderated by: A. Lawson

2 What is Cryptography?

3 What is your definition of cryptography?
krɪpˈtɒɡrəfi/ noun the art of writing or solving codes. What is your definition of cryptography? Cryptography Definition:  is the practice and study of techniques for secure communication in the presence of third parties called adversaries. Cryptography is derived from the Greek word ‘kryptos’ which means hidden or secret

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

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

6 Cryptography What does this hieroglyphic message say?
Write your answer below: (refer to website hieroglyphics code sheet)

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

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

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

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

11 Cryptography A D B E G ? Z ?

12 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

13 Decode the following message: FURVV WKH ULYHU WRQLJKW
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 WRQLJKW

14 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

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

16 Cryptography Why might Julius Caesar encrypt 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

17 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

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


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