Google Play In App Billing.How to perform signature verification step?

In my android app, I used google play’s in app billing.
I can purchase the items in my app and my credit card has paid.
Then , I need to perform signature verification.
However the value of ‘event.transaction.recepit’ was like that 64382835091xx96 or 90328327062xx88, (xx are two numbers) and the server telled me that they can’t handle that data.

How can I get the data that the server need to perform signature verification step through corona’s IAP api?

Thanks very much!

http://developer.android.com/guide/market/billing/billing_overview.html#billing-security

http://blog.anscamobile.com/2012/03/getting-started-with-android-in-app-billing/

http://developer.anscamobile.com/reference/in-app-purchases
[import]uid: 82934 topic_id: 27023 reply_id: 327023[/import]

We need the signature too, how can we get these values? [import]uid: 88922 topic_id: 27023 reply_id: 117839[/import]