#include <EEPROM.h> // We are going to read and write PICC's UIDs from/to EEPROM
#include <SPI.h> // RC522 Module uses SPI protocol
#include <MFRC522.h> // Library for Mifare RC522 Devices
#define SS_PIN 10
#define RST_PIN 9
byte storedCard[4] = {123, 456, 789, 012}; // Stores an ID read from EEPROM - I CHANGED THIS FOR SECURITY PURPOSES.
byte readCard[4]; // Stores scanned ID read from RFID Module
byte masterCard[4];
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance.
void setup() {
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
digitalWrite(6, HIGH);
digitalWrite(7, HIGH);
digitalWrite(8, HIGH);
digitalWrite(9, HIGH);
//Protocol Configuration
Serial.begin(9600); // Initialize serial communications with PC
SPI.begin(); // MFRC522 Hardware uses SPI protocol
mfrc522.PCD_Init(); // Initialize MFRC522 Hardware
//If you set Antenna Gain to Max it will increase reading distance
mfrc522.PCD_SetAntennaGain(mfrc522.RxGain_max);
}
///////////////////////////////////////// Main Loop ///////////////////////////////////
void loop () {
if ( ! mfrc522.PICC_IsNewCardPresent()) { //If a new PICC placed to RFID reader continue
return;
}
if ( ! mfrc522.PICC_ReadCardSerial()) { //Since a PICC placed get Serial and continue
return;
}
for (int i = 0; i < 4; i++) {
readCard[I] = mfrc522.uid.uidByte[I];
}
mfrc522.PICC_HaltA();
if (checkTwo(readCard, storedCard)) {
unlock();
delay(10000);
lock();
software_Reset();
}
}
boolean checkTwo ( byte a[], byte b[] ) {
boolean match;
if ( a[0] != NULL ) // Make sure there is something in the array first
match = true; // Assume they match at first
for ( int k = 0; k < 4; k++ ) { // Loop 4 times
if ( a[k] != b[k] ) // IF a != b then set match = false, one fails, all fail
match = false;
}
return match;
}
void lock() {
Serial.println("Lock");
digitalWrite(6, LOW);
digitalWrite(9, LOW);
delay(100);
digitalWrite(9, HIGH);
digitalWrite(6, HIGH);
}
void unlock() {
Serial.println("Unlock");
digitalWrite(7, LOW);
digitalWrite(8, LOW);
delay(100);
digitalWrite(8, HIGH);
digitalWrite(7, HIGH);
}
void software_Reset() // Restarts program from beginning but does not reset the peripherals and registers
{
asm volatile (" jmp 0");
}
They're a lot of fun 
