title: Android one time password (OTP) user registration/opening account
body: <p>I want to implement <strong>OTP functionality</strong> in my <strong>android</strong> application.
  In this application, <strong>after signup</strong> user will receive <strong>one time password key</strong>. After <strong>verifying OTP</strong>, user will be able to <strong>register/open account successfully</strong> by using that OTP. What i need to do achieve this?</p>