diff --git a/tempest/api/identity/admin/v3/test_credentials.py b/tempest/api/identity/admin/v3/test_credentials.py
index d22b27f..048c53a 100644
--- a/tempest/api/identity/admin/v3/test_credentials.py
+++ b/tempest/api/identity/admin/v3/test_credentials.py
@@ -53,11 +53,11 @@
     @test.attr(type='smoke')
     @test.idempotent_id('7cd59bf9-bda4-4c72-9467-d21cab278355')
     def test_credentials_create_get_update_delete(self):
-        keys = [data_utils.rand_name('Access'),
-                data_utils.rand_name('Secret')]
+        blob = '{"access": "%s", "secret": "%s"}' % (
+            data_utils.rand_name('Access'), data_utils.rand_name('Secret'))
         cred = self.creds_client.create_credential(
-            keys[0], keys[1], self.user_body['id'],
-            self.projects[0])['credential']
+            user_id=self.user_body['id'], project_id=self.projects[0],
+            blob=blob, type='ec2')['credential']
         self.addCleanup(self._delete_credential, cred['id'])
         for value1 in self.creds_list[0]:
             self.assertIn(value1, cred)
@@ -66,9 +66,10 @@
 
         new_keys = [data_utils.rand_name('NewAccess'),
                     data_utils.rand_name('NewSecret')]
+        blob = '{"access": "%s", "secret": "%s"}' % (new_keys[0], new_keys[1])
         update_body = self.creds_client.update_credential(
-            cred['id'], access_key=new_keys[0], secret_key=new_keys[1],
-            project_id=self.projects[1])['credential']
+            cred['id'], blob=blob, project_id=self.projects[1],
+            type='ec2')['credential']
         self.assertEqual(cred['id'], update_body['id'])
         self.assertEqual(self.projects[1], update_body['project_id'])
         self.assertEqual(self.user_body['id'], update_body['user_id'])
@@ -89,10 +90,11 @@
         fetched_cred_ids = list()
 
         for i in range(2):
+            blob = '{"access": "%s", "secret": "%s"}' % (
+                data_utils.rand_name('Access'), data_utils.rand_name('Secret'))
             cred = self.creds_client.create_credential(
-                data_utils.rand_name('Access'),
-                data_utils.rand_name('Secret'),
-                self.user_body['id'], self.projects[0])['credential']
+                user_id=self.user_body['id'], project_id=self.projects[0],
+                blob=blob, type='ec2')['credential']
             created_cred_ids.append(cred['id'])
             self.addCleanup(self._delete_credential, cred['id'])
 
diff --git a/tempest/services/identity/v3/json/credentials_client.py b/tempest/services/identity/v3/json/credentials_client.py
index decf3a8..7d4cf9a 100644
--- a/tempest/services/identity/v3/json/credentials_client.py
+++ b/tempest/services/identity/v3/json/credentials_client.py
@@ -13,6 +13,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+"""
+http://developer.openstack.org/api-ref-identity-v3.html#credentials-v3
+"""
+
 from oslo_serialization import jsonutils as json
 
 from tempest.common import service_client
@@ -21,17 +25,13 @@
 class CredentialsClient(service_client.ServiceClient):
     api_version = "v3"
 
-    def create_credential(self, access_key, secret_key, user_id, project_id):
-        """Creates a credential."""
-        blob = "{\"access\": \"%s\", \"secret\": \"%s\"}" % (
-            access_key, secret_key)
-        post_body = {
-            "blob": blob,
-            "project_id": project_id,
-            "type": "ec2",
-            "user_id": user_id
-        }
-        post_body = json.dumps({'credential': post_body})
+    def create_credential(self, **kwargs):
+        """Creates a credential.
+
+        Available params: see http://developer.openstack.org/
+                              api-ref-identity-v3.html#createCredential
+        """
+        post_body = json.dumps({'credential': kwargs})
         resp, body = self.post('credentials', post_body)
         self.expected_success(201, resp.status)
         body = json.loads(body)
@@ -39,22 +39,12 @@
         return service_client.ResponseBody(resp, body)
 
     def update_credential(self, credential_id, **kwargs):
-        """Updates a credential."""
-        body = self.get_credential(credential_id)['credential']
-        cred_type = kwargs.get('type', body['type'])
-        access_key = kwargs.get('access_key', body['blob']['access'])
-        secret_key = kwargs.get('secret_key', body['blob']['secret'])
-        project_id = kwargs.get('project_id', body['project_id'])
-        user_id = kwargs.get('user_id', body['user_id'])
-        blob = "{\"access\": \"%s\", \"secret\": \"%s\"}" % (
-            access_key, secret_key)
-        post_body = {
-            "blob": blob,
-            "project_id": project_id,
-            "type": cred_type,
-            "user_id": user_id
-        }
-        post_body = json.dumps({'credential': post_body})
+        """Updates a credential.
+
+        Available params: see http://developer.openstack.org/
+                              api-ref-identity-v3.html#updateCredential
+        """
+        post_body = json.dumps({'credential': kwargs})
         resp, body = self.patch('credentials/%s' % credential_id, post_body)
         self.expected_success(200, resp.status)
         body = json.loads(body)