Locked box keypad

// v 0.1

#include <Keypad.h>
#include <EEPROM.h>

const byte password_length = 4; // max. 511!
int relay_pin = 13;
int setkey_pin = 12;
int tone_pin = A0;
int time_over = 3000;

char password[password_length];
char initial_password[password_length];
int i=0;
long defTime;
char key_pressed=0;
bool f1=false;
const byte rows = 4;
const byte columns = 3;
char Keys[rows][columns] = {
{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'*','0','#'}
};

byte row_pins[rows] = {5,6,7,8};
byte column_pins[columns] = {2,3,4};

Keypad keypad_key = Keypad( makeKeymap(Keys), row_pins, column_pins, rows, columns);

void setup() {
  Serial.begin(115200);
  Serial.println("Start ...");
  if (password_length<2 or password_length>511) {
    Serial.println("Wrong Password length! Terminated program");
    while(1);
  }
  pinMode(tone_pin, OUTPUT);
  pinMode(relay_pin, OUTPUT);
  digitalWrite(relay_pin, LOW);
  pinMode(setkey_pin, INPUT_PULLUP);
  delay(500);
  Serial.println("Enter Password");
  //initialPassword(); // If not remember the password, run this once!
  readPassword();
  tone(tone_pin, 500, 200);
  delay(100);
  tone(tone_pin, 700, 200);
  delay(100);
  tone(tone_pin, 900, 200);
}

void loop() {
  if (defTime+time_over<millis() and f1==true) {
    f1=false;
    i=0;
    Serial.println("Time over");
    tone(tone_pin, 400, 200);
    delay(300);
    tone(tone_pin, 400, 200);
    delay(300);
    tone(tone_pin, 400, 200);
    Serial.println("Enter Password");
  }
  key_pressed = keypad_key.getKey();
  if(!digitalRead(setkey_pin)) change();
  if (key_pressed) {
    tone(tone_pin, 1000, 100);
    Serial.println(key_pressed);
    defTime=millis();
    f1=true;
    password[i++]=key_pressed;
  }
  if(i==password_length) {
    f1=false;
    delay(200);
    if(!(strncmp(password, initial_password,4))) {
      Serial.println("Password OK");
      tone(tone_pin, 500, 200);
      delay(100);
      tone(tone_pin, 700, 200);
      delay(100);
      tone(tone_pin, 900, 200);
      delay(100);
      tone(tone_pin, 700, 200);
      delay(100);
      tone(tone_pin, 500, 200);
      digitalWrite(relay_pin, HIGH);
      delay(1000);
      digitalWrite(relay_pin, LOW);
      Serial.println("Enter Password");
      i=0;
    }
    else
    {
      Serial.println("Password Fail");
      tone(tone_pin, 300, 500);
      delay(1000);
      Serial.println("Enter Password");
      i=0;
    }
  }
}

void change() {
  Serial.println("Change Password");
  delay(200);
  int j=0;
  while(!digitalRead(setkey_pin)) {
    char key_pressed=keypad_key.getKey();
    if (key_pressed) {
      tone(tone_pin, 1000, 100);
      Serial.println(key_pressed);
      password[i++]=key_pressed;
      if (i==password_length) {
        writePassword();
        i=0;
        Serial.println("Password done.");
        tone(tone_pin, 500, 200);
        delay(100);
        tone(tone_pin, 700, 200);
        delay(100);
        tone(tone_pin, 900, 200);
      }
    }
  }
  Serial.println("While end");
}

void initialPassword(){
  for(int j=0;j<password_length;j++) {
    EEPROM.write(j, 1); // The new password many 1 number. e.a. if length=4, the pass=1111.
  }
}

void readPassword(){
  for(int j=0;j<password_length;j++) {
    initial_password[j]=EEPROM.read(j);
  }
}

void writePassword(){
  for(int j=0;j<password_length;j++) {
    EEPROM.write(j, password[j]);
    initial_password[j]=password[j];
  }
}