diff --git a/shadowsocks/obfsplugin/auth_chain.py b/shadowsocks/obfsplugin/auth_chain.py
index 49bafdc..bed2ffa 100644
--- a/shadowsocks/obfsplugin/auth_chain.py
+++ b/shadowsocks/obfsplugin/auth_chain.py
@@ -87,19 +87,20 @@ class xorshift128plus(object):
         y = self.v1
         self.v0 = y
         x ^= ((x & xorshift128plus.mov_mask) << 23)
-        x ^= (y ^ (x >> 17) ^ (y >> 26)) & xorshift128plus.max_int
+        x ^= (y ^ (x >> 17) ^ (y >> 26))
         self.v1 = x
         return (x + y) & xorshift128plus.max_int
 
     def init_from_bin(self, bin):
-        bin += b'\0' * 16
+        if len(bin) < 16:
+            bin += b'\0' * 16
         self.v0 = struct.unpack('<Q', bin[:8])[0]
         self.v1 = struct.unpack('<Q', bin[8:16])[0]
 
     def init_from_bin_len(self, bin, length):
-        bin += b'\0' * 16
-        bin = struct.pack('<H', length) + bin[2:]
-        self.v0 = struct.unpack('<Q', bin[:8])[0]
+        if len(bin) < 16:
+            bin += b'\0' * 16
+        self.v0 = struct.unpack('<Q', struct.pack('<H', length) + bin[2:8])[0]
         self.v1 = struct.unpack('<Q', bin[8:16])[0]
 
         for i in range(4):
diff --git a/shadowsocks/tcprelay.py b/shadowsocks/tcprelay.py
index e4b8fbe..45a650e 100644
--- a/shadowsocks/tcprelay.py
+++ b/shadowsocks/tcprelay.py
@@ -1163,8 +1163,9 @@ class TCPRelayHandler(object):
             self._protocol.dispose()
             self._protocol = None
 
-        self._encryptor.dispose()
-        self._encryptor = None
+        if self._encryptor:
+            self._encryptor.dispose()
+            self._encryptor = None
         self._dns_resolver.remove_callback(self._handle_dns_resolved)
         self._server.remove_handler(self)
         if self._add_ref > 0: