Time based one time password generator, based on RFC6238 and Google Authenticator

otp.py

#!/usr/bin/python
import array
import base64
import hmac
import math
import sha
import time
from hashlib import sha1



def get_otp(key, step):
	hashed = hmac.new(key,step,sha1)
	binary = array.array('B', hashed.hexdigest().decode('hex'));
	offset = binary[19]&0x0F
	binary = ((binary[offset] & 0x7F)<<24)|((binary[offset+1]&0xFF)<<16)|((binary[offset+2]&0xFF)<<8)|(binary[offset+3]&0xFF);
	return '%06d'%(binary%1000000)


def calc_step():
	now = math.floor(time.time())
	step = int(math.floor(now/30))
	result = hex(step).replace('0x','')
	while(len(result)<16):
		result = '0'+result
	return result.decode('hex')



if(__name__=='__main__'):
	key = base64.b32decode("JBSWY3DPEHPK3PXP")
	step = calc_step()
	print get_otp(key, step)