Working with some of our partners, Truecopy has in past few days been able to successfully demonstrate Digital Signing of GST returns in GSTN sandbox. Anyone who has dealt with the available documentation (or lack thereof) on GSTN signatures would be able to tell you that this definitely deserves a blog post!
Without getting into the details (because GSTN has not asked for our opinion), we want to state that we do not believe that the signature format that GSTN seems to accept is a suitable one. However, we will keep our disagreement aside and help all our partners get their returns accepted in their sandbox.
PS> We also hope there are no more changes to spec, and the same signature formats continue to be accepted tomorrow.