We're using the AIM method (Advanced Integration Method). The AIM documentation just referred to it as MD5 Hash but I bet they're using the HMAC-M5 just as their SIM does.

I'll have to try that and see if the hash values match.

Thanks for your help!

Rodd

>Rodd,
>That is correct Authorize.net is using HMAC-M5 as per there documentation on page: 7 of the Simple Integration Method Implementation Guide v1.0
>
>Chad Newman