encrypted-walkie-talkie/code/code.ino

//TODO: Learn how to use mic. in arduino, transmit plain sound among two arduinos and play it
//TODO: Implement encryption and decryption using AES128, test it with text, then use to encrypt sound

#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <AESLib.h>
#include <EEPROM.h>

//Components
LiquidCrystal_I2C lcd(0x27, 16, 2);
RF24 radio(9,10); // CE, CSN
const byte micPin = A0;


//Settings
//byte unsigned address = 1;
const byte address[6] = "00001";

byte key = 97;
byte unsigned screen = 0;
const char seed[32] = "555bfda9ba33008ceba78321683ed8e"; // random seed, MUST BE 31 chars long
char password[32];
bool mode = 0; // 0 = transmit, 1 = recieve
bool encryption = 1; // will the trafic be encrypted?

bool isScreenChanged = true; // we must display first time

//Switch screen button
const byte switchScreenButton = A1;
byte switchScreenLast;

//IncreaseButton
const byte increaseButton = A2;
byte increaseButtonLast;

//DecreaseButton
const byte decreaseButton = A3;
byte decreaseButtonLast;

void switchMode();
void printOutput();
void updatePassword();
void encryptDecyptData();

//short micValue = 337; 
//const short micBaseline = 337;// 3.3v / 2 = 1.56v, 1.56/5*1024 = 337.

const byte micValuesLength = 16;
short micValues[micValuesLength];

void setup() {
  Serial.begin(9600);
  pinMode(micPin, INPUT);
  //Setting up buttons
  pinMode(switchScreenButton, INPUT_PULLUP);
  pinMode(increaseButton, INPUT_PULLUP);
  pinMode(decreaseButton, INPUT_PULLUP);
  
  //Setting up a radio module
  radio.begin();
  radio.setPALevel(RF24_PA_MAX);
  radio.setChannel(0x00);
  radio.setDataRate(RF24_250KBPS);
  switchMode(); //default is recieving
  //Setting up a LCD
  lcd.init();
  lcd.backlight();
  
  updatePassword();
}

void loop() {
  if (!mode) {// transmit
    for (int i = 0; i < micValuesLength; i ++) {
      micValues[i] = analogRead(micPin) << 2;
    }
    if (encryption)
      encryptDecyptData();
    radio.write(micValues, 32);
  } else { // receive
    if (radio.available()) {
      radio.read(micValues, 32);
      if (encryption)
        encryptDecyptData();
      for (int i = 0; i < micValuesLength; i++) {
        PORTD = micValues[i];
      }
    }
  }
 
  byte switchButtonValue = digitalRead(switchScreenButton);
  byte increaseValue = digitalRead(increaseButton);
  byte decreaseValue = digitalRead(decreaseButton);
  
  
  if (switchButtonValue == 0 && switchScreenLast == 1) {
    screen = screen < 3? screen + 1 : 0;
    isScreenChanged = true;
  }

  if ((decreaseValue == 0 && decreaseButtonLast == 1) || increaseValue == 0 && increaseButtonLast == 1) {
    isScreenChanged = true;
    switch (screen) {
      case 0:
        mode = !mode;
      break;
      case 1:
        if (decreaseValue == 0 && decreaseButtonLast == 1)
//          address = address > 0? address - 1 : 127;
            1+1;
        else
//          address = address < 127? address + 1 : 0;
            1+1;
      break;
      case 2:
        if (decreaseValue == 0 && decreaseButtonLast == 1){
          key --;
        } else {
          key ++;
        }
      break;
      case 3:
        encryption = !encryption;
      break;
    }
  }
  
  switchScreenLast = switchButtonValue;
  increaseButtonLast = increaseValue;
  decreaseButtonLast = decreaseValue;
  if (isScreenChanged)
    printOutput();
}

void switchMode () {
  if (!mode) {    // transmit -> recieve
//    radio.openReadingPipe(0, 0x0123456789LL);
radio.openReadingPipe(0, address);
    radio.startListening();
  } else {        // recieve -> transmit
    radio.openWritingPipe(address);
    radio.stopListening();
  }
  
  mode = !mode;
}

void printOutput () {
   lcd.clear();
   switch (screen) {
    case 0:
      lcd.print("Mode: ");
      lcd.print(mode? "receive" : "transmit");
    break;
    case 1:
      lcd.print("Address: ");
//      lcd.print(address);
    break;
    case 2:
      lcd.print("Password: ");
      lcd.print(key);
    break;
    case 3:
      lcd.print("Encryption: ");
      lcd.print(encryption? "yes" : "no");
   }
   
   isScreenChanged = false;
   
//   for (int i = 0; i < 5; i ++) lcd.print(address[i] - '0');
   //lcd.print(mode);
}

void updatePassword() {
  for (int i = 0; i < 31; i ++) {
    password[i] = seed[i];
  }
  password[31] = (char)key;
}

void encryptDecyptData () {
  for (int i = 0; i < micValuesLength; i ++) {
    char localKey[2];
    localKey[0] = password[2 * i];
    localKey[1] = password[2 * i + 1];
    Serial.print("Before:");
    Serial.print(micValues[i]);
    micValues[i] = micValues[i] ^ (short)localKey;
    Serial.print(",After:");
    Serial.println(micValues[i]);
  }
}