diff --git a/shadowsocks/obfsplugin/auth_chain.py b/shadowsocks/obfsplugin/auth_chain.py
index 3cff2ec..f219eac 100644
--- a/shadowsocks/obfsplugin/auth_chain.py
+++ b/shadowsocks/obfsplugin/auth_chain.py
@@ -47,9 +47,19 @@ def create_auth_chain_b(method):
     return auth_chain_b(method)
 
 
+def create_auth_chain_c(method):
+    return auth_chain_c(method)
+
+
+def create_auth_chain_d(method):
+    return auth_chain_d(method)
+
+
 obfs_map = {
     'auth_chain_a': (create_auth_chain_a,),
     'auth_chain_b': (create_auth_chain_b,),
+    'auth_chain_c': (create_auth_chain_c,),
+    'auth_chain_d': (create_auth_chain_d,),
 }
 
 
@@ -724,3 +734,105 @@ class auth_chain_b(auth_chain_a):
         if buf_size > 400:
             return random.next() % 521
         return random.next() % 1021
+
+
+class auth_chain_c(auth_chain_b):
+    def __init__(self, method):
+        super(auth_chain_c, self).__init__(method)
+        self.salt = b"auth_chain_c"
+        self.no_compatible_method = 'auth_chain_c'
+        self.data_size_list0 = []
+
+    def init_data_size(self, key):
+        if self.data_size_list0:
+            self.data_size_list0 = []
+        random = xorshift128plus()
+        random.init_from_bin(key)
+        # 补全数组长为12~24-1
+        list_len = random.next() % (8 + 16) + (4 + 8)
+        for i in range(0, list_len):
+            self.data_size_list0.append((int)(random.next() % 2340 % 2040 % 1440))
+        self.data_size_list0.sort()
+
+    def set_server_info(self, server_info):
+        self.server_info = server_info
+        try:
+            max_client = int(server_info.protocol_param.split('#')[0])
+        except:
+            max_client = 64
+        self.server_info.data.set_max_client(max_client)
+        self.init_data_size(self.server_info.key)
+
+    def rnd_data_len(self, buf_size, last_hash, random):
+        other_data_size = buf_size + self.server_info.overhead
+        # final_pos 总是分布在pos~(data_size_list0.len-1)之间
+        # 除非data_size_list0中的任何值均过小使其全部都无法容纳buf
+        if other_data_size >= self.data_size_list0[-1]:
+            if other_data_size >= 1440:
+                return 0
+            if other_data_size > 1300:
+                return random.next() % 31
+            if other_data_size > 900:
+                return random.next() % 127
+            if other_data_size > 400:
+                return random.next() % 521
+            return random.next() % 1021
+
+        random.init_from_bin_len(last_hash, buf_size)
+        pos = bisect.bisect_left(self.data_size_list0, other_data_size)
+        # random select a size in the leftover data_size_list0
+        final_pos = pos + random.next() % (len(self.data_size_list0) - pos)
+        return self.data_size_list0[final_pos] - other_data_size
+
+
+class auth_chain_d(auth_chain_b):
+    def __init__(self, method):
+        super(auth_chain_d, self).__init__(method)
+        self.salt = b"auth_chain_d"
+        self.no_compatible_method = 'auth_chain_d'
+        self.data_size_list0 = []
+
+    def check_and_patch_data_size(self, random):
+        # append new item
+        # when the biggest item(first time) or the last item(other time) are not big enough.
+        # but set a limit size (64) to avoid stack over follow.
+        if self.data_size_list0[-1] < 1000 and len(self.data_size_list0) < 64:
+            self.data_size_list0.append((int)(random.next() % 2340 % 2040 % 1440))
+            self.check_and_patch_data_size(random)
+
+    def init_data_size(self, key):
+        if self.data_size_list0:
+            self.data_size_list0 = []
+        random = xorshift128plus()
+        random.init_from_bin(key)
+        # 补全数组长为12~24-1
+        list_len = random.next() % (8 + 16) + (4 + 8)
+        for i in range(0, list_len):
+            self.data_size_list0.append((int)(random.next() % 2340 % 2040 % 1440))
+        self.data_size_list0.sort()
+        old_len = len(self.data_size_list0)
+        self.check_and_patch_data_size(random)
+        # if check_and_patch_data_size are work, re-sort again.
+        if old_len != len(self.data_size_list0):
+            self.data_size_list0.sort()
+
+    def set_server_info(self, server_info):
+        self.server_info = server_info
+        try:
+            max_client = int(server_info.protocol_param.split('#')[0])
+        except:
+            max_client = 64
+        self.server_info.data.set_max_client(max_client)
+        self.init_data_size(self.server_info.key)
+
+    def rnd_data_len(self, buf_size, last_hash, random):
+        other_data_size = buf_size + self.server_info.overhead
+        # if other_data_size > the bigest item in data_size_list0, not padding any data
+        if other_data_size >= self.data_size_list0[-1]:
+            return 0
+
+        random.init_from_bin_len(last_hash, buf_size)
+        pos = bisect.bisect_left(self.data_size_list0, other_data_size)
+        # random select a size in the leftover data_size_list0
+        final_pos = pos + random.next() % (len(self.data_size_list0) - pos)
+        return self.data_size_list0[final_pos] - other_data_size