Integrating paymnet gateway "Instamojo" in Laravel 5.1

I'm using a package 'IndiPay' (http://ift.tt/1rB6V5a) in Laravel 5.1. I have configured api_key and auth_token in my .env file. And in the parameters list, included the required POST parameters (purpose and amount). Additionally, added tid with reference to the GitHub. Even though, I couldn't make the payment successful. It throwed an error like problem in Hash parameter. I attach my screenshot here.

Any suggestions please?

Thanks in advance..

via Chebli Mohamed