HMAC

Fields	Input
Payload	{"ss":"1","msg":{"netsMid":"UMID_877772003","tid":"","submissionMode":"B","txnAmount":"1000","merchantTxnRef":"20180719 04:12:48","merchantTxnDtm":"20180719 04:12:48.672","paymentType":"SALE","currencyCode":"SGD","paymentMode":"","merchantTimeZone":"+8:00","b2sTxnEndURL":"https://httpbin.org/post","b2sTxnEndURLParam":"","s2sTxnEndURL":"https://sit2.enets.sg/MerchantApp/rest/s2sTxnEnd","s2sTxnEndURLParam":"","clientType":"W","supMsg":"","netsMidIndicator":"U","ipAddress":"127.0.0.1","language":"en"}}
Secret Key
Signature

HMAC Calculator