Hello Ankit
I am not sure if you are already aware of this. DigestLoginModule is not supported by SAP. Although DigestLoginModule is available in sap documentation and also available in the list of available login modules in visual admin and nwa, but it does not work and was not meant to work in the past. I have asked the responsible colleagues in sap to change sap documentation accordingly. It will take some time. I faced similar situation with another customer and this what i told him too.
Please post back should you need any further clarification.
Cheers
Tapan