Notes

Types of Encryption Symmetric Encryption (Private Key Encryption) The same key is used for both encryption and decryption Faster but requires securely sharing the key between parties Example: AES (Advance Encryption Standard) used for securing files Asymmetric Encryption (Public Key Encryption) Uses a pair of keys: Public Key (for encryption) Private key (for decryption) More secure for internet communications since users don’t need to share a single key. Hashing (One-way encryption) Converts data into a fixed length string that cannot be reversed Used for storing passwordss securely. Example: SHA-256 (Secure Hash Algorithm) used in blockchain and password security.

  • To prevent this, we must
    • never click on links in texts from unknown numbers
    • never contact our bank or service provider directly if we recieve a suspicious text
    • and enable spam filters on our phones to block spam messages
import random

def caesar_cipher(text, shift, mode):
    result = ""
    shift = shift % 26  # Ensure shifts wrap around correctly

    if mode not in ["encrypt", "decrypt"]:
        return "Invalid mode! Please enter 'encrypt' or 'decrypt'."

    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

# User input with basic validation
mode = input("Do you want to encrypt or decrypt? ").strip().lower()
if mode not in ["encrypt", "decrypt"]:
    print("Invalid mode! Please enter 'encrypt' or 'decrypt'.")
else:
    message = input("Enter your message: ")
    shift_input = input("Enter shift value (number of places to shift or 'random'): ").strip().lower()
    
    if shift_input == "random":
        shift = random.randint(1, 25)  # Pick a random shift value between 1 and 25
        print(f"Random shift selected: {shift}")
    else:
        try:
            shift = int(shift_input)
        except ValueError:
            print("Invalid shift value! Please enter a number or 'random'.")
            shift = None
    
    if shift is not None:
        output = caesar_cipher(message, shift, mode)
        print(f"Result: {output}")

Result: xn
  • ✅ Allows “random” as a shift input – The user can type “random”, and the program will select a random integer between 1 and 25.
  • ✅ Prints the selected random shift – So the user knows what shift was applied.
  • ✅ Preserves original functionality – Users can still input a manual shift value if they prefer.
  • ✅ Handles invalid inputs – Ensures only valid numbers or “random” are accepted.