diff --git a/shadowsocks/obfsplugin/auth.py b/shadowsocks/obfsplugin/auth.py
index 4495040..54ca924 100644
--- a/shadowsocks/obfsplugin/auth.py
+++ b/shadowsocks/obfsplugin/auth.py
@@ -59,7 +59,9 @@ def create_auth_aes128_sha1(method):
 
 obfs_map = {
         'auth_sha1': (create_auth_sha1,),
+        'auth_sha1_compatible': (create_auth_sha1,),
         'auth_sha1_v2': (create_auth_sha1_v2,),
+        'auth_sha1_v2_compatible': (create_auth_sha1_v2,),
         'auth_sha1_v3': (create_auth_sha1_v3,),
         'auth_sha1_v4': (create_auth_sha1_v4,),
         'auth_aes128': (create_auth_aes128,),
@@ -81,6 +83,7 @@ class auth_base(plain.plain):
     def __init__(self, method):
         super(auth_base, self).__init__(method)
         self.method = method
+        self.no_compatible_method = ''
 
     def init_data(self):
         return ''
@@ -102,7 +105,9 @@ class auth_base(plain.plain):
 
     def not_match_return(self, buf):
         self.raw_trans = True
-        return (b'E'*2048, False)
+        if self.method == self.no_compatible_method:
+            return (b'E'*2048, False)
+        return (buf, False)
 
 class client_queue(object):
     def __init__(self, begin_id):
@@ -211,6 +216,7 @@ class auth_sha1(auth_base):
         self.client_id = 0
         self.connection_id = 0
         self.max_time_dif = 60 * 60 # time dif (second) setting
+        self.no_compatible_method = 'auth_sha1'
 
     def init_data(self):
         return obfs_auth_data()
@@ -432,6 +438,7 @@ class auth_sha1_v2(auth_base):
         self.client_id = 0
         self.connection_id = 0
         self.salt = b"auth_sha1_v2"
+        self.no_compatible_method = 'auth_sha1_v2'
 
     def init_data(self):
         return obfs_auth_v2_data()
@@ -620,214 +627,6 @@ class auth_sha1_v2(auth_base):
             self.decrypt_packet_num += 1
         return (out_buf, sendback)
 
-class auth_sha1_v3(auth_base):
-    def __init__(self, method):
-        super(auth_sha1_v3, self).__init__(method)
-        self.recv_buf = b''
-        self.unit_len = 8100
-        self.decrypt_packet_num = 0
-        self.raw_trans = False
-        self.has_sent_header = False
-        self.has_recv_header = False
-        self.client_id = 0
-        self.connection_id = 0
-        self.max_time_dif = 60 * 60 * 24 # time dif (second) setting
-        self.salt = b"auth_sha1_v3"
-
-    def init_data(self):
-        return obfs_auth_v2_data()
-
-    def set_server_info(self, server_info):
-        self.server_info = server_info
-        try:
-            max_client = int(server_info.protocol_param)
-        except:
-            max_client = 64
-        self.server_info.data.set_max_client(max_client)
-
-    def rnd_data(self, buf_size):
-        if buf_size > 1200:
-            return b'\x01'
-
-        if buf_size > 400:
-            rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 256)
-        else:
-            rnd_data = os.urandom(struct.unpack('>H', os.urandom(2))[0] % 512)
-
-        if len(rnd_data) < 128:
-            return common.chr(len(rnd_data) + 1) + rnd_data
-        else:
-            return common.chr(255) + struct.pack('>H', len(rnd_data) + 3) + rnd_data
-
-    def pack_data(self, buf):
-        data = self.rnd_data(len(buf)) + buf
-        data = struct.pack('>H', len(data) + 6) + data
-        adler32 = zlib.adler32(data) & 0xFFFFFFFF
-        data += struct.pack('<I', adler32)
-        return data
-
-    def pack_auth_data(self, buf):
-        if len(buf) == 0:
-            return b''
-        data = self.rnd_data(len(buf)) + buf
-        data_len = len(data) + 16
-        crc = binascii.crc32(self.salt + self.server_info.key + struct.pack('>H', data_len)) & 0xFFFFFFFF
-        data = struct.pack('<I', crc) + data
-        data = struct.pack('>H', data_len) + data
-        data += hmac.new(self.server_info.iv + self.server_info.key, data, hashlib.sha1).digest()[:10]
-        return data
-
-    def auth_data(self):
-        utc_time = int(time.time()) & 0xFFFFFFFF
-        if self.server_info.data.connection_id > 0xFF000000:
-            self.server_info.data.local_client_id = b''
-        if not self.server_info.data.local_client_id:
-            self.server_info.data.local_client_id = os.urandom(4)
-            logging.debug("local_client_id %s" % (binascii.hexlify(self.server_info.data.local_client_id),))
-            self.server_info.data.connection_id = struct.unpack('<I', os.urandom(4))[0] & 0xFFFFFF
-        self.server_info.data.connection_id += 1
-        return b''.join([struct.pack('<I', utc_time),
-                self.server_info.data.local_client_id,
-                struct.pack('<I', self.server_info.data.connection_id)])
-
-    def client_pre_encrypt(self, buf):
-        ret = b''
-        if not self.has_sent_header:
-            head_size = self.get_head_size(buf, 30)
-            datalen = min(len(buf), random.randint(0, 31) + head_size)
-            ret += self.pack_auth_data(self.auth_data() + buf[:datalen])
-            buf = buf[datalen:]
-            self.has_sent_header = True
-        while len(buf) > self.unit_len:
-            ret += self.pack_data(buf[:self.unit_len])
-            buf = buf[self.unit_len:]
-        ret += self.pack_data(buf)
-        return ret
-
-    def client_post_decrypt(self, buf):
-        if self.raw_trans:
-            return buf
-        self.recv_buf += buf
-        out_buf = b''
-        while len(self.recv_buf) > 2:
-            length = struct.unpack('>H', self.recv_buf[:2])[0]
-            if length >= 8192 or length < 7:
-                self.raw_trans = True
-                self.recv_buf = b''
-                raise Exception('client_post_decrypt data error')
-            if length > len(self.recv_buf):
-                break
-
-            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
-                self.raw_trans = True
-                self.recv_buf = b''
-                raise Exception('client_post_decrypt data uncorrect checksum')
-
-            pos = common.ord(self.recv_buf[2])
-            if pos < 255:
-                pos += 2
-            else:
-                pos = struct.unpack('>H', self.recv_buf[3:5])[0] + 2
-            out_buf += self.recv_buf[pos:length - 4]
-            self.recv_buf = self.recv_buf[length:]
-
-        if out_buf:
-            self.decrypt_packet_num += 1
-        return out_buf
-
-    def server_pre_encrypt(self, buf):
-        if self.raw_trans:
-            return buf
-        ret = b''
-        while len(buf) > self.unit_len:
-            ret += self.pack_data(buf[:self.unit_len])
-            buf = buf[self.unit_len:]
-        ret += self.pack_data(buf)
-        return ret
-
-    def server_post_decrypt(self, buf):
-        if self.raw_trans:
-            return (buf, False)
-        self.recv_buf += buf
-        out_buf = b''
-        if not self.has_recv_header:
-            if len(self.recv_buf) < 6:
-                return (b'', False)
-            crc = struct.pack('<I', binascii.crc32(self.salt + self.server_info.key + self.recv_buf[:2]) & 0xFFFFFFFF)
-            if crc != self.recv_buf[2:6]:
-                return self.not_match_return(self.recv_buf)
-            length = struct.unpack('>H', self.recv_buf[:2])[0]
-            if length > len(self.recv_buf):
-                return (b'', False)
-            sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, self.recv_buf[:length - 10], hashlib.sha1).digest()[:10]
-            if sha1data != self.recv_buf[length - 10:length]:
-                logging.error('auth_sha1_v3 data uncorrect auth HMAC-SHA1')
-                return self.not_match_return(self.recv_buf)
-            pos = common.ord(self.recv_buf[6])
-            if pos < 255:
-                pos += 6
-            else:
-                pos = struct.unpack('>H', self.recv_buf[7:9])[0] + 6
-            out_buf = self.recv_buf[pos:length - 10]
-            if len(out_buf) < 12:
-                logging.info('auth_sha1_v3: too short, data %s' % (binascii.hexlify(self.recv_buf),))
-                return self.not_match_return(self.recv_buf)
-            utc_time = struct.unpack('<I', out_buf[:4])[0]
-            client_id = struct.unpack('<I', out_buf[4:8])[0]
-            connection_id = struct.unpack('<I', out_buf[8:12])[0]
-            time_dif = common.int32(utc_time - (int(time.time()) & 0xffffffff))
-            if time_dif < -self.max_time_dif or time_dif > self.max_time_dif:
-                logging.info('auth_sha1_v3: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
-                return self.not_match_return(self.recv_buf)
-            elif self.server_info.data.insert(client_id, connection_id):
-                self.has_recv_header = True
-                out_buf = out_buf[12:]
-                self.client_id = client_id
-                self.connection_id = connection_id
-            else:
-                logging.info('auth_sha1_v3: auth fail, data %s' % (binascii.hexlify(out_buf),))
-                return self.not_match_return(self.recv_buf)
-            self.recv_buf = self.recv_buf[length:]
-            self.has_recv_header = True
-
-        sendback = False
-        while len(self.recv_buf) > 2:
-            length = struct.unpack('>H', self.recv_buf[:2])[0]
-            if length >= 8192 or length < 7:
-                self.raw_trans = True
-                self.recv_buf = b''
-                if self.decrypt_packet_num == 0:
-                    logging.info('auth_sha1_v3: over size')
-                    return (b'E'*2048, False)
-                else:
-                    raise Exception('server_post_decrype data error')
-            if length > len(self.recv_buf):
-                break
-
-            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
-                logging.info('auth_sha1_v3: checksum error, data %s' % (binascii.hexlify(self.recv_buf[:length]),))
-                self.raw_trans = True
-                self.recv_buf = b''
-                if self.decrypt_packet_num == 0:
-                    return (b'E'*2048, False)
-                else:
-                    raise Exception('server_post_decrype data uncorrect checksum')
-
-            pos = common.ord(self.recv_buf[2])
-            if pos < 255:
-                pos += 2
-            else:
-                pos = struct.unpack('>H', self.recv_buf[3:5])[0] + 2
-            out_buf += self.recv_buf[pos:length - 4]
-            self.recv_buf = self.recv_buf[length:]
-            if pos == length - 4:
-                sendback = True
-
-        if out_buf:
-            self.server_info.data.update(self.client_id, self.connection_id)
-            self.decrypt_packet_num += 1
-        return (out_buf, sendback)
-
 class auth_sha1_v4(auth_base):
     def __init__(self, method):
         super(auth_sha1_v4, self).__init__(method)
@@ -841,6 +640,7 @@ class auth_sha1_v4(auth_base):
         self.connection_id = 0
         self.max_time_dif = 60 * 60 * 24 # time dif (second) setting
         self.salt = b"auth_sha1_v4"
+        self.no_compatible_method = 'auth_sha1_v4'
 
     def init_data(self):
         return obfs_auth_v2_data()
@@ -1065,6 +865,7 @@ class auth_aes128(auth_base):
         self.connection_id = 0
         self.max_time_dif = 60 * 60 * 24 # time dif (second) setting
         self.salt = b"auth_aes128"
+        self.no_compatible_method = 'auth_aes128'
         self.extra_wait_size = struct.unpack('>H', os.urandom(2))[0] % 1024
         self.pack_id = 0
         self.recv_id = 0
@@ -1583,3 +1384,4 @@ class auth_aes128_sha1(auth_base):
         if hmac.new(user_key, buf[:-4], self.hashfunc).digest()[:4] != buf[-4:]:
             return b''
         return buf[:-8]
+