The Nebula Raider has intercepted a suspicious message from an enemy ship. To ensure the safety of the crew and the ship, it is crucial to decrypt this message. The intercepted message is encoded using a simple Caesar cipher, and your task is to build a device that can decrypt it. The message that needs to be decoded is

“ulcly nvpun av npcl fvb bw”

Components Needed:

Raspberry Pi Pico WH Microcontroller

LCD1602 IIC/I2C Blue Backlight Display

Push buttons (2 for navigation, 1 for decryption)

Resistors

Breadboard

Jumper wires

Instructions:

Set Up the Circuit:

Connect the LCD1602 display to the Raspberry Pi Pico using the I2C interface (SDA to GP0, SCL to GP1).

Connect three push buttons to GPIO pins on the Raspberry Pi Pico (e.g., Navigation buttons to GP2 and GP3, Decrypt button to GP4).

Use resistors to ensure proper current flow and connect the push buttons in a pull-down configuration.

Circuit Diagram

Write the Code:

Open your coding environment and write the following Python code to create the decryption device.

from machine import Pin, I2C
import utime
from lcd_api import LcdApi
from i2c_lcd import I2cLcd
 
# LCD setup
I2C_ADDR = 0x27
I2C_NUM_ROWS = 2
I2C_NUM_COLS = 16
 
i2c = I2C(0, scl=Pin(1), sda=Pin(0), freq=400000)
lcd = I2cLcd(i2c, I2C_ADDR, I2C_NUM_ROWS, I2C_NUM_COLS)
 
# Button setup
button_up = Pin(2, Pin.IN, Pin.PULL_DOWN)
button_down = Pin(3, Pin.IN, Pin.PULL_DOWN)
button_decrypt = Pin(4, Pin.IN, Pin.PULL_DOWN)
 
# Caesar Cipher decryption function
def decrypt_caesar_cipher(text, shift):
    decrypted = ""
    for char in text:
        if char.isalpha():
            shift_amount = 65 if char.isupper() else 97
            decrypted += chr((ord(char) - shift_amount - shift) % 26 + shift_amount)
        else:
            decrypted += char
    return decrypted
 
# Initial setup
lcd.clear()
lcd.putstr("Decrypt Message")
shift = 0
encrypted_message = "ucy nvuh nc b bw"
 
while True:
    if button_up.value():
        shift = (shift + 1) % 26
        lcd.clear()
        lcd.putstr("Shift: {}".format(shift))
        utime.sleep(0.3)
    elif button_down.value():
        shift = (shift - 1) % 26
        lcd.clear()
        lcd.putstr("Shift: {}".format(shift))
        utime.sleep(0.3)
    elif button_decrypt.value():
        decrypted_message = decrypt_caesar_cipher(encrypted_message, shift)
        lcd.clear()
        lcd.putstr("Decrypting...")
        utime.sleep(1)
        lcd.clear()
        lcd.putstr("Message: ")
        lcd.move_to(0, 1)
        lcd.putstr(decrypted_message[:16])
        utime.sleep(5)
        lcd.clear()
        lcd.putstr("Shift: {}".format(shift))
    utime.sleep(0.1)

Test the System:

Upload the code to the Raspberry Pi Pico and run it.

Use the up and down buttons to adjust the shift value.

Press the decrypt button to decrypt the message using the selected shift value.

Observe the decrypted message displayed on the LCD.

Learning Outcomes:

Cryptography Basics: Understand the principles of the Caesar cipher and how to decrypt it.

Microcontroller Programming: Develop skills in writing code to read input from buttons and display data on an LCD.

Problem Solving: Enhance problem-solving abilities by implementing a decryption algorithm and creating an interactive device.

Extension Ideas:

Multiple Messages: Extend the project by allowing the decryption of multiple messages stored in an array.

Encryption: Add functionality to encrypt messages using the Caesar

cipher, making the device capable of both encryption and decryption.

User Interface: Improve the user interface by adding more buttons for

additional controls and a more detailed display of the decrypted

message.

By completing this project, you will have built a device capable of decrypting Caesar cipher messages, enhancing the security measures on the Nebula Raider and helping the crew stay ahead of enemy threats. Your work will demonstrate your ability to tackle cryptographic challenges and contribute to the mission’s success.

Day 9: sus

Circuit Diagram