See PaymentSense's own documentation regarding setup within their admin area.

Make sure that the hashing type matches the Kartris plugin version you are using. You can check the version of the DLL you have by navigating to it in Windows explorer, right-clicking and choosing 'properties', then viewing the details tab. Newer versions of Kartris also show this DLL version number within the list of payment systems.

If it's the older DLL (v1.x), then you should use MD5. If it's the newer v2.x DLL (introduced in Kartris v2.9013) then use SHA1 (if using this version, your Kartris should have a 'HashMethod' setting withing the PaymentSense settings).