Introduction to Cryptography PDF

10/28/2024 Introduction to Cryptography Ms Roberta Portelli 1 What is Cryptography? Cryptography is a way to keep messages secret It involves encoding information so others can't re...

10/28/2024 Introduction to Cryptography Ms Roberta Portelli 1 What is Cryptography? Cryptography is a way to keep messages secret It involves encoding information so others can't read it Only the intended recipient can decode the message Why do you think keeping messages secret might be important? Ms Roberta Portelli 2 1  10/28/2024 A Simple Example Paul wants to send a secret message to his friend far away He can't just hand it to his friend directly The message might be seen by others along the way How could Paul keep his message private? Ms Roberta Portelli 3 Plain Text vs. Cipher Text Plain text: A message anyone can read (like English) Cipher text: An encoded message only the recipient can understand Paul needs to convert his plain text to cipher text Can you think of a simple way to encode a message? Ms Roberta Portelli 4 2  10/28/2024 The Encryption Process Step 1: Convert the message to numbers Step 2: Use a special key to change those numbers Step 3: The result is cipher text - a secret code! Only someone with the right key can decode it Ms Roberta Portelli 5 Sending the Secret Message Paul can now safely send his cipher text message Even if someone intercepts it, they can't read it Only Paul's friend has the key to decode it What might happen if someone without the key found the message? Ms Roberta Portelli 6 3  10/28/2024 The Decryption Process Paul's friend receives the cipher text They use a special decryption key This key converts the cipher text back to numbers Then the numbers become plain text again Ms Roberta Portelli 7 Why Use Cryptography? Keeps private information safe Protects messages from being read by others Allows secure communication over long distances Where in your life might cryptography be useful? Ms Roberta Portelli 8 4  10/28/2024 Types of Keys Encryption key: Used to encode the message Decryption key: Used to decode the message Both sender and receiver need to know the right keys How do you think they could share keys securely? Ms Roberta Portelli 9 Modern Cryptography Uses complex math to create stronger codes Computers can quickly encode and decode messages Used in many areas like online banking and messaging Can you name some apps or websites that might use cryptography? Ms Roberta Portelli 10 5