diff --git a/shadowsocks/crypto/m2.py b/shadowsocks/crypto/m2.py
index 4082db0..a1d7d1c 100644
--- a/shadowsocks/crypto/m2.py
+++ b/shadowsocks/crypto/m2.py
@@ -96,4 +96,4 @@ def test_rc4():
 
 
 if __name__ == '__main__':
-    test_aes_128_cfb()
\ No newline at end of file
+    test_aes_128_cfb()
diff --git a/shadowsocks/crypto/rc4_md5.py b/shadowsocks/crypto/rc4_md5.py
index 952962f..b9cd72b 100644
--- a/shadowsocks/crypto/rc4_md5.py
+++ b/shadowsocks/crypto/rc4_md5.py
@@ -67,4 +67,4 @@ def test():
 
 
 if __name__ == '__main__':
-    test()
\ No newline at end of file
+    test()
diff --git a/shadowsocks/crypto/salsa20_ctr.py b/shadowsocks/crypto/salsa20_ctr.py
index 759aa03..0ea13b8 100644
--- a/shadowsocks/crypto/salsa20_ctr.py
+++ b/shadowsocks/crypto/salsa20_ctr.py
@@ -23,7 +23,6 @@
 from __future__ import absolute_import, division, print_function, \
     with_statement
 
-import time
 import struct
 import logging
 import sys