Digital Lockpick Microbit Lab

• Digital Lockpick Microbit Lab
  • Features
  • Video
  • Description
  • Prerequisite Skills
  • Learned Skills
  • Materials
  • Getting Familiar
• Helper class provided by the helpful folks at microbit-playground
  • Setup
  • Crack The Lock!
    • Medium Lockbox
    • Hard Lockbox
  • Next Steps

Features

• Estimated Time: 1 Hour (basic; base lab) - 4 Hours (advanced; enhancements)

• Appropriate Grades: 6-12

• Topic Alignment ( Limited, Medium, High )

• GenCyber Cybersecurity First Principles:

  GenCyber CFPs	Alignment
  Data Hiding	H
  Least Privilege	L
  Abstraction	M
  Domain Separation	L
  Resource Encapsulation	M
  Simplicity	H
  Modularity	M
  Process Isolation	H
  Layering	H
  Minimization	M

• GenCyber Cybersecurity Concepts:

  GenCyber CCs	Alignment
  Defense in Depth	M
  Confidentiality	H
  Integrity	L
  Availability	H
  Think Like an Adversary	M
  Keep It Simple	H

Video

Description

Prerequisite Skills

Learned Skills

• Servo Motor Basics
  * Click here for information on servo motors
  * Click here for Micro::Bit servo basics

• Radio Signal Basics

  • Click here for information on radio signals
  • Click here for Micro::Bit radio basics

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Materials

Note that many keys can be used with a single lock box.

Getting Familiar

Control Servo(Javascript)

from microbit import *

Helper class provided by the helpful folks at microbit-playground
class Servo:
"""
A simple class for controlling hobby servos.
Args:
    pin (pin0 .. pin3): The pin where servo is connected.
    freq (int): The frequency of the signal, in hertz.
    min_us (int): The minimum signal length supported by the servo.
    max_us (int): The maximum signal length supported by the servo.
    angle (int): The angle between minimum and maximum positions.
Usage:
    SG90 @ 3.3v servo connected to pin0
    = Servo(pin0).write_angle(90)
"""

def __init__(self, pin, freq=50, min_us=600, max_us=2400, angle=180):
    self.min_us = min_us
    self.max_us = max_us
    self.us = 0
    self.freq = freq
    self.angle = angle
    self.analog_period = 0
    self.pin = pin
    analog_period = round((1/self.freq) * 1000)  # hertz to miliseconds
    self.pin.set_analog_period(analog_period)

def write_us(self, us):
    us = min(self.max_us, max(self.min_us, us))
    duty = round(us * 1024 * self.freq // 1000000)
    self.pin.write_analog(duty)
    self.pin.write_digital(0)  # turn the pin off

def write_angle(self, degrees=None):
    degrees = degrees % 360
    total_range = self.max_us - self.min_us
    us = self.min_us + total_range * degrees // self.angle
    self.write_us(us)
Servo(pin16).write_angle(0) # Turn motor once
Serve(pin16).write_angle(95) # Turn motor again

Control Radio(Javascript)

    from microbit import *  
    import radio   
radio_group = 1 #number of radio frequency to use  
radio.on()  
radio.config(power=7,channel=radio_group)  
radio.send("Hello")
  

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Setup

Below is listed sections of code for a very basic lockbox that can be opened multiple ways. First, pressing the A/B buttons will unlock the box (not very secure but remember this is our starter box). Secondly, this box will also open if the binary encoding of the number 5 ("0101") is sent over the radio using radio channel 1.
Here we see the beginning of the program, where the microbit initializes the radio group("channel"), then tells the lock to move to position 0, and finally shows us the sprite "No".

//initial setup of the block 
radio.setGroup(1)
let position = 0
pins.digitalWritePin(DigitalPin.P16, position)
basic.showIcon(IconNames.No)

Now, in order to unlock the box using the buttons we must tell the microbit to listen for the "On-Click" event that triggered every time the physical button is pushed. Since we initially set the position of our lock to 0, we say that pressing the button A will unlock the box by telling the lock to move to position 95 which is our unlocked position. ?What does the code for the B button which closes the box look like?

//listen for a click event, then un/lock box
input.onButtonPressed(Button.A, () => {
    basic.showString("A")
    position = 95
    pins.servoWritePin(AnalogPin.P16, position)
    basic.pause(100)
})

And now we show the code responsible for listening for a key to come over the radio to unlock the box. If the string that is received is equal to the secret key string then we will either lock or unlock the box, depending on the position that the lock is already in.

radio.onDataPacketReceived(({ receivedString }) => {
    if (receivedString == "0101") {
        if (position == 160) {
            position = 20
        } else {
            position = 160
        }
        pins.servoWritePin(AnalogPin.P16, position)
    }
})

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Crack The Lock!

Medium Lockbox

Hard Lockbox

Next Steps

The GenCyber Wyoming COWPOKES program is supported by the National Security Agency and the National Science Foundation through Award #H98230-18-1-0095. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the National Security Agency, or the U.S. government.