diff --git a/shadowsocks/obfsplugin/verify_simple.py b/shadowsocks/obfsplugin/verify_simple.py
index c162c06..43f8c3e 100644
--- a/shadowsocks/obfsplugin/verify_simple.py
+++ b/shadowsocks/obfsplugin/verify_simple.py
@@ -338,6 +338,7 @@ class obfs_auth_data(object):
     def __init__(self):
         self.sub_obfs = None
         self.client_id = {}
+        self.startup_time = int(time.time() - 30) & 0xffffffff
 
     def update(self, client_id, connection_id):
         if client_id in self.client_id:
@@ -491,7 +492,7 @@ class auth_simple(verify_base):
                 client_id = struct.unpack('<I', out_buf[4:8])[0]
                 connection_id = struct.unpack('<I', out_buf[8:12])[0]
                 time_dif = common.int32((int(time.time()) & 0xffffffff) - utc_time)
-                if time_dif < 60 * -3 or time_dif > 60 * 3:
+                if time_dif < 60 * -3 or time_dif > 60 * 3 or common.int32(utc_time - self.server_info.data.startup_time) < 0:
                     self.raw_trans = True
                     self.recv_buf = b''
                     logging.info('auth_simple: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
diff --git a/shadowsocks/tcprelay.py b/shadowsocks/tcprelay.py
index 5d1f251..f82762b 100644
--- a/shadowsocks/tcprelay.py
+++ b/shadowsocks/tcprelay.py
@@ -115,8 +115,6 @@ class TCPRelayHandler(object):
                                             config['method'])
         self._encrypt_correct = True
         self._obfs = obfs.obfs(config['obfs'])
-        if server.obfs_data is None:
-            server.obfs_data = self._obfs.init_data()
         server_info = obfs.server_info(server.obfs_data)
         server_info.host = config['server']
         server_info.port = server._listen_port
@@ -769,7 +767,7 @@ class TCPRelay(object):
         self.server_transfer_ul = 0
         self.server_transfer_dl = 0
         self.server_connections = 0
-        self.obfs_data = None
+        self.obfs_data = obfs.obfs(config['obfs']).init_data()
 
         self._timeout = config['timeout']
         self._timeouts = []  # a list for all the handlers