diff --git a/sdk/auth/crediantial.go b/sdk/auth/crediantial.go
index 29338e7..4fd6cbe 100644
--- a/sdk/auth/crediantial.go
+++ b/sdk/auth/crediantial.go
@@ -1,4 +1,12 @@
 package auth
 
+import "golib.gaore.com/GaoreGo/gaore-common-sdk-go/sdk/utils"
+
+var debug utils.Debug
+
+func init() {
+	debug = utils.Init("signer")
+}
+
 type Credential interface {
 }
diff --git a/sdk/auth/rpc_signature_composer.go b/sdk/auth/rpc_signature_composer.go
index c30619d..a57f079 100644
--- a/sdk/auth/rpc_signature_composer.go
+++ b/sdk/auth/rpc_signature_composer.go
@@ -88,6 +88,8 @@ func unsignRpcRequest(request *http.Request, signer Signer) (err error) {
 	signValue, ok := signParams["sign"]
 	if !ok {
 		return errors.New("sign value is not exists")
+	} else {
+		delete(signParams, "sign")
 	}
 
 	stringToSign := utils.GetUrlFormedMap(signParams)
@@ -96,6 +98,7 @@ func unsignRpcRequest(request *http.Request, signer Signer) (err error) {
 	stringToSign = strings.Replace(stringToSign, "%7E", "~", -1)
 	stringToSign = url.QueryEscape(stringToSign)
 	stringToSign = request.Method + "&%2F&" + stringToSign
+	debug("grsdk singstring %s", stringToSign)
 
 	if timestamp, err := strconv.ParseInt(signParams["access_time"], 10, 64); err != nil {
 		return err