I couldn't able to generate hmac signature which is much required in every platform for validations and no such capability is figured in service now,I don't know any one faced this issue or not.
I referred this discussion as well but its not working as per the code provided :
https://www.servicenow.com/community/developer-forum/alternative-solution-for-generating-hmac-sha256...
Highly appreciated for quick support here!!!
