diff --git a/shadowsocks/obfsplugin/auth_chain.py b/shadowsocks/obfsplugin/auth_chain.py
index 9a2ce80..849f08e 100644
--- a/shadowsocks/obfsplugin/auth_chain.py
+++ b/shadowsocks/obfsplugin/auth_chain.py
@@ -884,9 +884,7 @@ class auth_chain_f(auth_chain_e):
             self.key_change_interval = int(server_info.protocol_param.split('#')[1])  # config are in second
         except:
             self.key_change_interval = 60 * 60 * 24  # a day by second
-
-    def on_recv_auth_data(self, utc_time):
-        self.key_change_datetime_key = int(utc_time / self.key_change_interval)
+        self.key_change_datetime_key = int(int(time.time()) / self.key_change_interval)
         self.key_change_datetime_key_bytes = []  # big bit first list
         for i in range(7, -1, -1):  # big-ending compare to c
             self.key_change_datetime_key_bytes.append((self.key_change_datetime_key >> (8 * i)) & 0xFF)
@@ -898,13 +896,9 @@ class auth_chain_f(auth_chain_e):
         random = xorshift128plus()
         # key xor with key_change_datetime_key
         new_key = bytearray(key)
-        new_key_str = ''
         for i in range(0, 8):
             new_key[i] ^= self.key_change_datetime_key_bytes[i]
-            new_key_str += chr(new_key[i])
-        for i in range(8, len(new_key)):
-            new_key_str += chr(new_key[i])
-        random.init_from_bin(to_bytes(new_key_str))
+        random.init_from_bin(new_key)
         # 补全数组长为12~24-1
         list_len = random.next() % (8 + 16) + (4 + 8)
         for i in range(0, list_len):