how to implement one time password

Hope you are doing good.
could you please help me in implementing One time password .

Wiith Thanks & Regards
Syed Riyaz
what is the problem you are encountering?
what is your approach to do so?

i need to add wcf service in my application and service should return return one time password for the customer.
but unable to bussiness logic and how to Integrate this service in outsystems.