problem for authorize.net in service merchant plugin

Hello,

I used service merchant plugin in my application. using "paypal getway"
it works fine.

But when i tried authorize.net as a getway, it dose not work. It gives
error

StandardError in SubscriptionsController#subscribe
Recurring payment creation error: User authentication failed due to
invalid authentication values.

When i debug the code I think one file (i.e may be
authorizenet_extension.rb) is missing in

"vendor\plugins\service_merchant\recurring_billing\lib\am_extensions"

There is only paypal_extension.rb is present for paypal getway. but not
like "authorize.net_extension.rb" for authorize.net getway.

Am I right?

If the authorizenet_extension.rb is missing, please tell me whether
should I get that file.
Please guide me where I'm doing wrong?