diff --git a/shadowsocks/crypto/m2.py b/shadowsocks/crypto/m2.py
deleted file mode 100644
index 4c7e148..0000000
--- a/shadowsocks/crypto/m2.py
+++ /dev/null
@@ -1,117 +0,0 @@
-#!/usr/bin/env python
-
-# Copyright (c) 2014 clowwindy
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-# SOFTWARE.
-
-from __future__ import absolute_import, division, print_function, \
-    with_statement
-
-import sys
-import logging
-
-__all__ = ['ciphers']
-
-has_m2 = True
-try:
-    __import__('M2Crypto')
-except ImportError:
-    has_m2 = False
-
-
-def create_cipher(alg, key, iv, op, key_as_bytes=0, d=None, salt=None, i=1,
-                  padding=1):
-
-    import M2Crypto.EVP
-    return M2Crypto.EVP.Cipher(alg.replace('-', '_'), key, iv, op,
-                               key_as_bytes=0, d='md5', salt=None, i=1,
-                               padding=1)
-
-
-def err(alg, key, iv, op, key_as_bytes=0, d=None, salt=None, i=1, padding=1):
-    logging.error(('M2Crypto is required to use %s, please run'
-                   ' `apt-get install python-m2crypto`') % alg)
-    sys.exit(1)
-
-
-if has_m2:
-    ciphers = {
-        b'aes-128-cfb': (16, 16, create_cipher),
-        b'aes-192-cfb': (24, 16, create_cipher),
-        b'aes-256-cfb': (32, 16, create_cipher),
-        b'bf-cfb': (16, 8, create_cipher),
-        b'camellia-128-cfb': (16, 16, create_cipher),
-        b'camellia-192-cfb': (24, 16, create_cipher),
-        b'camellia-256-cfb': (32, 16, create_cipher),
-        b'cast5-cfb': (16, 8, create_cipher),
-        b'des-cfb': (8, 8, create_cipher),
-        b'idea-cfb': (16, 8, create_cipher),
-        b'rc2-cfb': (16, 8, create_cipher),
-        b'rc4': (16, 0, create_cipher),
-        b'seed-cfb': (16, 16, create_cipher),
-    }
-else:
-    ciphers = {}
-
-
-def run_method(method):
-    from shadowsocks.crypto import util
-
-    cipher = create_cipher(method, b'k' * 32, b'i' * 16, 1)
-    decipher = create_cipher(method, b'k' * 32, b'i' * 16, 0)
-
-    util.run_cipher(cipher, decipher)
-
-
-def check_env():
-    # skip this test on pypy and Python 3
-    try:
-        import __pypy__
-        del __pypy__
-        from nose.plugins.skip import SkipTest
-        raise SkipTest
-    except ImportError:
-        pass
-    if bytes != str:
-        from nose.plugins.skip import SkipTest
-        raise SkipTest
-
-
-def test_aes_128_cfb():
-    check_env()
-    run_method(b'aes-128-cfb')
-
-
-def test_aes_256_cfb():
-    check_env()
-    run_method(b'aes-256-cfb')
-
-
-def test_bf_cfb():
-    check_env()
-    run_method(b'bf-cfb')
-
-
-def test_rc4():
-    check_env()
-    run_method(b'rc4')
-
-
-if __name__ == '__main__':
-    test_aes_128_cfb()