Safe Computing

• • 2 min read

Big Idea 5: Safe Computing

Big Idea 5: Safe Computing

Protecting Personally Identifiable Information (PII) and staying secure online

What is PII?

PII (Personally Identifiable Information) refers to data that can be used to identify an individual online.

  • Social Security Number
  • Email Address
  • Full Name
  • Driver’s License

Cookies 🍪

Cookies store user data, including preferences and PII, often to track behavior and improve experience.

  • Session Cookies: Deleted when the browser closes
  • Persistent Cookies: Remain for a set time, even after browser closes
  • First-Party Cookies: Set by the website itself
  • Third-Party Cookies: Set by advertisers or external sites

⚠️ Risk: Cookies can collect private info, preferences, and track you across the web

Popcorn Hack 1: Cookie Hunt

Open Developer Tools (F12 → Application → Cookies)

  • Find: Name, Value, Expiration Date
  • Determine if it’s session, persistent, first- or third-party

Password Security 🔐

Passwords should be:

  • At least 10 characters
  • Include uppercase + lowercase
  • Contain numbers
  • Contain symbols

Encryption 🔒

Encryption transforms data into unreadable form for unauthorized users.

Symmetric

  • Same key for encrypt/decrypt
  • Example: AES

Asymmetric

  • Public key to encrypt, private to decrypt
  • Used in HTTPS & secure messaging

Hashing

  • One-way: irreversible
  • Used in password storage, blockchains (SHA-256)

Where it's Used

  • HTTPS (SSL/TLS)
  • End-to-End Messaging Apps

Phishing 🎣

Tricking users into giving personal info by pretending to be a trusted source.

Email Phishing

  • Fake emails asking for info
  • Don't click unknown links
  • Check domain: suspicious-looking emails

Website Spoofing

  • Fake websites mimicking real ones
  • Manually type URLs
  • Look for https:// and padlock icon

Smishing (SMS Phishing)

  • Texts pretending to be banks, gov’t, etc.
  • Don't click unknown text links
  • Enable spam filters

Verification ✅

Multi-Factor Authentication (MFA)

Combines passwords with secondary methods like SMS, email codes, or apps (Google Authenticator).

Digital Signatures

Verify that documents or software weren’t tampered with using hashes + encryption.

CAPTCHA 🤖

Verifies you’re human using simple puzzles or image selection.

Popcorn Hack 2: Try CAPTCHA

Visit a website with CAPTCHA and try to break it 😎

Homework Hacks 🧠

Hack 1: MCQ Review

Go over questions on safe computing (PII, phishing, encryption).

Hack 2: Caesar Cipher Code

import random
def caesar_cipher(text, shift, mode):
    result = ""
    for char in text:
        if char.isalpha():
            shift_amount = shift if mode == "encrypt" else -shift
            new_char = chr(((ord(char.lower()) - 97 + shift_amount) % 26) + 97)
            result += new_char.upper() if char.isupper() else new_char
        else:
            result += char
    return result
mode = input("Encrypt or decrypt? ").strip().lower()
message = input("Enter your message: ")

# If user chooses "random" for shift
shift_input = input("Enter shift (or type 'random'): ").strip().lower()
shift = random.randint(1, 25) if shift_input == "random" else int(shift_input)

output = caesar_cipher(message, shift, mode)
print(f"Result: {output}")

✨ Run in a Jupyter Notebook and try different messages!