Discrete synchronization time window

This feature was developed for OneSpan Mobile Security Suite.

Unlike a classic hardware Digipass authenticator (Digipass 300, Digipass GO 1 etc.), a mobile phone clock will change after daylight savings adjustment. With the discrete time window, Authentication Suite Server SDK supports this daylight savings adjustment and is able to accept an OTP generated on the mobile phone even with a time difference of +/- 1 hour.

Figure:  Static time window

Figure:  Discrete synchronization time window

With a static or dynamic time window, the purpose of the SyncWindow parameter is to define the time window accepted during the first authentication (or signature validation) or after a reset.

In the discrete synchronization time window mode, the purpose of the SyncWindow parameter is to determine the number of accepted discrete time windows. To support the daylight savings adjustment, SyncWindow must be set to 3 so that OTPs generated at GMT, GMT+1, or GMT-1 will be accepted.

This functionality is enabled by adding the SW_DISCRETE flag to the SyncWindow runtime parameter, for example SyncWindow = 3 | SW_DISCRETE.

It is not possible to combine the dynamic time window and the discrete synchronization time window. The TW_DYNAMIC_WINDOWS flag has no effect if the SW_DISCRETE flag is set.

For an example of the discrete time window, refer to Appendix: Discrete time window calculation example.