The two way OTP authentication module is an integration module with the portal which acts as an Identity Provider (IdP). The concept used for this authentication module is to have two simple one time passwords (OTP) of 6 digits. There is two-way communication involved which makes the two combined codes a strong authentication method. The two way OTP authentication module should be configured as a custom IdP in the Onegini Token Server admin console.
More information about Two-way OTP can be found here.