ArduinoOTP.ino

/*
 One Time Password
 
 */

#include <stdarg.h>
#include <LiquidCrystal.h>
#include "sha1.h" 

#include <SPI.h>
#include <Wire.h>
#include "RTClib.h"
#include "RTC_DS3234.h"


RTC_DS3234 RTC(8);
LiquidCrystal lcd(7, 6, 2, 3, 4, 5);


uint8_t hmacKey1[]={
 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0xde, 0xad, 0xbe, 0xef 
};

uint8_t time[]={
   0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 
};



void printHash(uint8_t* hash, int length) {
  int i;
  for (i=0; i<length; i++) {
    Serial.print("0123456789abcdef"[hash[i]>>4]);
    Serial.print("0123456789abcdef"[hash[i]&0xf]);
  }
  Serial.println();
}


void lcdHash(uint8_t* hash, int length) {
  int i;
  
  char str[length*2 + 1];
  
  for (i=0; i<length; i++) {
    str[i*2] = "0123456789abcdef"[hash[i]>>4];
    str[i*2+1] = "0123456789abcdef"[hash[i]&0xf];
  }
  str[i*2] = '\0';
  
  lcd.print(str);
}
  
void setup()  { 
  
  Serial.begin(9600);
  SPI.begin();
  RTC.begin();  
  lcd.begin(16, 2);
}

void loop() {
  
  uint8_t* hash;
  uint8_t otp[4];
  uint32_t a;
 
  Serial.print("Secret : ");
  printHash(hmacKey1, 10);
  
   DateTime now = RTC.now();

    Serial.println(now.toString(buf,len));
    
    Serial.print(" since midnight 1/1/1970 = ");
    Serial.print(now.unixtime());
    
  //uint32_t x = RTC.now().unixtime() / 30;
  long epoch = 123456;
  time[4] =  (byte )((epoch >> 24) & 0xff);
  time[5] = (byte )((epoch >> 16) & 0xff);
  time[6] = (byte )((epoch >> 8) & 0xff);
  time[7] = (byte )((epoch ) & 0xff);
  
  Serial.print("Time : ");
  printHash(time, 8);
  //lcdHash(time, 8);

  Sha1.initHmac(hmacKey1, 10);
  Sha1.writebytes(time, 8);

  hash = Sha1.resultHmac();      
  Serial.print("HMAC : ");   
  printHash(hash, 20);
  
  memset(otp,0,4);
  int offset = hash[19] & 0x0f;
  memcpy(otp, hash + offset, 4);
  
  unsigned long o=0x22000000;
  unsigned long l= 0x7FFFFFFF;
  long val = ((long )otp[0] & 0x7F) << 24;
  val |= ((long )otp[1]) << 16;
  val |= ((long )otp[2]) << 8;
  val |= otp[3];
  
  val = val % 1000000;
  
  Serial.print("Code : ");   //needs to be left padded
  Serial.println(val);
  lcd.setCursor(0, 0);
  lcd.print(val);
  lcd.setCursor(0, 1);
  lcdHash(time, 8);
  
   
  delay(1000);
}