USAePay, looks like your hash example is wrong. Consider your example listed here: http://wiki.usaepay.com/developer/transactionapi?#calculating_hash_value
You use as input string sale:sd*s3j002jd:53.21:34576721:1234
, but claim it md5 hashes to 52d534dd45388432ac0a44c9174ffb3f
, but this is wrong.
Using Mac OS built-in md5
binary:
$md5 -s sale:sd*s3j002jd:53.21:3456721:1234
MD5 ("sale:sd*s3j002jd:53.21:3456721:1234") = 423ce7188315e73be5d81dbe7f28db22