diff --git a/shadowsocks/crypto/ctypes_libsodium.py b/shadowsocks/crypto/ctypes_libsodium.py
new file mode 100644
index 0000000..1e81060
--- /dev/null
+++ b/shadowsocks/crypto/ctypes_libsodium.py
@@ -0,0 +1,135 @@
+#!/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 logging
+from ctypes import CDLL, c_char_p, c_int, c_long, c_ulonglong, byref, \
+    create_string_buffer, c_void_p
+
+__all__ = ['ciphers']
+
+libsodium = None
+loaded = False
+
+buf_size = 2048
+
+# for salsa20 and chacha20
+BLOCK_SIZE = 64
+
+
+def load_libsodium():
+    global loaded, libsodium, buf
+
+    from ctypes.util import find_library
+    for p in ('sodium',):
+        libsodium_path = find_library(p)
+        if libsodium_path:
+            break
+    else:
+        raise Exception('libsodium not found')
+    logging.info('loading libsodium from %s', libsodium_path)
+    libsodium = CDLL(libsodium_path)
+    libsodium.sodium_init.restype = c_int
+    libsodium.crypto_stream_salsa20_xor_ic.restype = c_int
+    libsodium.crypto_stream_salsa20_xor_ic.argtypes = (c_void_p, c_char_p,
+                                                       c_ulonglong,
+                                                       c_char_p, c_ulonglong,
+                                                       c_char_p)
+    libsodium.crypto_stream_chacha20_xor_ic.restype = c_int
+    libsodium.crypto_stream_chacha20_xor_ic.argtypes = (c_void_p, c_char_p,
+                                                        c_ulonglong,
+                                                        c_char_p, c_ulonglong,
+                                                        c_char_p)
+
+    libsodium.sodium_init()
+
+    buf = create_string_buffer(buf_size)
+    loaded = True
+
+
+class Salsa20Crypto(object):
+    def __init__(self, cipher_name, key, iv, op):
+        if not loaded:
+            load_libsodium()
+        self.key = key
+        self.iv = iv
+        self.key_ptr = c_char_p(key)
+        self.iv_ptr = c_char_p(iv)
+        if cipher_name == b'salsa20':
+            self.cipher = libsodium.crypto_stream_salsa20_xor_ic
+        elif cipher_name == b'chacha20':
+            self.cipher = libsodium.crypto_stream_chacha20_xor_ic
+        else:
+            raise Exception('Unknown cipher')
+        # byte counter, not block counter
+        self.counter = 0
+
+    def update(self, data):
+        global buf_size, buf
+        l = len(data)
+
+        # we can only prepend some padding to make the encryption align to
+        # blocks
+        padding = self.counter % BLOCK_SIZE
+        if buf_size < padding + l:
+            buf_size = (padding + l) * 2
+            buf = create_string_buffer(buf_size)
+
+        if padding:
+            data = (b'\0' * padding) + data
+        self.cipher(byref(buf), c_char_p(data), padding + l,
+                    self.iv_ptr, int(self.counter / BLOCK_SIZE), self.key_ptr)
+        self.counter += l
+        # buf is copied to a str object when we access buf.raw
+        # strip off the padding
+        return buf.raw[padding:padding + l]
+
+
+ciphers = {
+    b'salsa20': (32, 8, Salsa20Crypto),
+    b'chacha20': (32, 8, Salsa20Crypto),
+}
+
+
+def test_salsa20():
+    from shadowsocks.crypto import util
+
+    cipher = Salsa20Crypto(b'salsa20', b'k' * 32, b'i' * 16, 1)
+    decipher = Salsa20Crypto(b'salsa20', b'k' * 32, b'i' * 16, 0)
+
+    util.run_cipher(cipher, decipher)
+
+
+def test_chacha20():
+    from shadowsocks.crypto import util
+
+    cipher = Salsa20Crypto(b'chacha20', b'k' * 32, b'i' * 16, 1)
+    decipher = Salsa20Crypto(b'chacha20', b'k' * 32, b'i' * 16, 0)
+
+    util.run_cipher(cipher, decipher)
+
+
+if __name__ == '__main__':
+    test_chacha20()
+    test_salsa20()