Arduino based RFID Authenticator

 February 14, 2022    Tinkering

An Arduino based device that generates a password from the UID of your RFID card. You can set your computer's password to the generated string and automatically log in with the swipe of the RFID card.

Supplies:

• Arduino Leonardo (needs to be HID compatible)
• RFID-Modul
• LED
• 220 Ohm Resistor
• Jumper Wire (female-male and female-female)

Electronic circuits:

Code:

GitHub Code

#include <MD5.h>
#include <SPI.h>
#include <Keyboard.h>
#include <MFRC522.h>

// Constants
#define RST_PIN 9
#define SS_PIN 10
#define LED_PIN 8

// Variables
String RFIDUID;

// Create MFRC522 instance
MFRC522 mfrc522(SS_PIN, RST_PIN);

void setup() {

  Serial.begin(9600);

  pinMode(LED_PIN, OUTPUT);

  // Init SPI and MFRC522
  while (!Serial);
  SPI.begin();
  mfrc522.PCD_Init();
  delay(4);
  Serial.println("RFID Password Authenticator");

}

// Read RFDI UID
void readRFID(byte *buffer, byte bufferSize)
{
  RFIDUID = "";
  for (byte i = 0; i < bufferSize; i++)
  {
    RFIDUID = RFIDUID + String(buffer[i], HEX);
  }
}

void writePass() 
{ 

  Serial.println("This ist your UID:" + RFIDUID);
  char buf[30];
  RFIDUID.toCharArray(buf,RFIDUID.length());
  digitalWrite(LED_PIN, HIGH);

  // MD5 Hash
  unsigned char* hash=MD5::make_hash(buf);
  char *md5str = MD5::make_digest(hash, 16);
  strncpy(buf, md5str, 10); // Password length 12

  Serial.print("This ist your password:");
  Serial.println(buf);

  // Type password
  Keyboard.print(buf);
  Keyboard.releaseAll();
  delay(100);
  Keyboard.press(KEY_RETURN);
  Keyboard.releaseAll();
  delay(1000);
  digitalWrite(LED_PIN, LOW);

}

void loop() 
{

  // Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle.
  if ( ! mfrc522.PICC_IsNewCardPresent()) 
  {
    return;
  }

  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial()) 
  {
    return;
  }

  readRFID(mfrc522.uid.uidByte, mfrc522.uid.size);
  writePass();

}