Hi,
The direct-post solution could be implemented in HikaShop but would have a weird integration.
This method use a form in the HikaShop website which would be submit directly to NAB, so the customer quit the HikaShop website to submit the form to NAB.
So, the payment form as to be at the end of the checkout, in a special page after the checkout.
The order would be created in the database and the payment form would be a special one. Not the classical HikaShop payment process.
The main problem is the "result url". The documentation does not clearly explain how it works but it said that the URL has to be secured thanks SSL.
So it does not have any advantage to use this solution regarding the last one.
The XML-Api solution could be implemented in HikaShop, in the same way of other hosted payment integration.
HikaShop would require a SSL certificate to secure the credit card information (between the customer and the shop).
All calls between HikaShop and NAB would be secured thanks to SSL and the API should provide all required features.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.