Computer Science
Grade 9
20 min
7. Data Privacy and Encryption
Introduce the concept of data privacy and how encryption can be used to protect sensitive information.
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Introduction & Learning Objectives
Learning Objectives
Define data privacy, encryption, plaintext, ciphertext, and key.
Explain the difference between symmetric and asymmetric encryption.
Identify at least three common risks to personal data privacy online.
Apply a Caesar cipher to encrypt a short message.
Apply a Caesar cipher to decrypt a short message.
Describe the role of a hash function in verifying data integrity.
Ever sent a secret note to a friend that you didn't want anyone else to read? 🤫 How do we make sure our digital messages on phones and computers are just as private?
This lesson explores the world of data privacy and encryption, the digital locks and keys that protect our information. We will learn how secret codes work in the digital world and why they are essential for keeping our per...
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Key Concepts & Vocabulary
TermDefinitionExample
Data PrivacyThe right of an individual to have control over how their personal information is collected, used, and shared.Choosing the privacy settings on your social media account to control who can see your photos and posts.
EncryptionThe process of converting readable data (plaintext) into a scrambled, unreadable format (ciphertext) using an algorithm and a key.Your banking app encrypts your password before sending it to the bank's server, so a hacker intercepting it would only see gibberish like 'Xq9z#A!p' instead of 'MyPassword123'.
Plaintext & CiphertextPlaintext is the original, human-readable message. Ciphertext is the encrypted, scrambled message.If the plaintext is 'MEET AT NOON', the ciphertext might be 'PHHW DW...
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Core Syntax & Patterns
Caesar Cipher Algorithm (Encryption)
ciphertext_letter = (plaintext_letter + key) % 26
Used to encrypt a message with a simple substitution cipher. For each letter in the plaintext, find its corresponding number (A=0, B=1...), add the key, use the modulo 26 operator to wrap around the alphabet if needed, and convert the result back to a letter.
Caesar Cipher Algorithm (Decryption)
plaintext_letter = (ciphertext_letter - key + 26) % 26
Used to decrypt a message encrypted with a Caesar cipher. For each letter in the ciphertext, find its corresponding number, subtract the key (adding 26 to avoid negative numbers), use the modulo 26 operator, and convert back to a letter.
The Principle of Strong Passwords
Combine uppercase letters, lowercase letters, numbers, and symbols....
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Challenging
If you intercepted a message encrypted with a Caesar cipher but did not know the key, what would be the most effective and straightforward strategy to decrypt it, given the nature of the cipher?
A.Try every possible key from 1 to 25 and see which one produces a readable message.
B.Use a supercomputer to analyze the ciphertext for complex patterns.
C.Ask the sender for their public key.
D.It is impossible to decrypt without the key.
Challenging
Alice wants to send a secret message to Bob using asymmetric encryption. She finds Bob's public key online and uses it to encrypt her message. Which key must Bob use to decrypt the message, and where should that key be kept?
A.Bob's public key, which he keeps on a public website.
B.Bob's private key, which he must keep secret and secure.
C.Alice's public key, which she must send to Bob.
D.Alice's private key, which she must keep secret and secure.
Challenging
Why is it more secure for a website to store user passwords as hashes instead of encrypting them?
A.Because hashing is faster than encryption.
B.Because a hash takes up less storage space than an encrypted password.
C.Because hashing is a one-way process, so if the database is stolen, the original passwords cannot be recovered, even by the website's owners.
D.Because encrypted passwords can only be read by the user, not the website.
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