diff --git a/sm4Drbg.py b/sm4Drbg.py
index 7dad911..4abbadd 100755
--- a/sm4Drbg.py
+++ b/sm4Drbg.py
@@ -22,13 +22,13 @@ class SM4_RNG:
 
         self.blocklen = 16
 
-        self.seed_material = ""
+        self.seed_material = b""
         self.sm4 = CryptSM4()
         self.SM4_RNG_Instantiate(personalization_string, nonce)
 
     def SM4_RNG_Instantiate(
         self, personalization_string: bytes = b"", nonce: bytes = b""
-    ):
+    ) -> None:
         self.min_entropy = self.min_entropy_input_length
         self.entropy_input = secrets.token_bytes(self.min_entropy)
         self.seed_material = self.entropy_input + nonce + personalization_string
@@ -39,12 +39,12 @@ class SM4_RNG:
         self.reseed_counter = 1
         self.last_reseed_time = int(time.time())
 
-    def SM4_RNG_Update(self, seed_material, Key, V):
+    def SM4_RNG_Update(self, seed_material: bytes, Key: bytes, V: bytes) -> None:
         temp = b""
         self.sm4.set_key(Key, SM4_ENCRYPT)
         while len(temp) < self.seedlen:
-            V = (int.from_bytes(V, "big") + 1) % (1 << self.blocklen)
-            self.output_block = self.sm4.crypt_ecb(V.to_bytes(self.blocklen, "big"))
+            V_int = (int.from_bytes(V, "big") + 1) % (1 << self.blocklen)
+            self.output_block = self.sm4.crypt_ecb(V_int.to_bytes(self.blocklen, "big"))
             temp = temp + self.output_block
         temp = temp[: self.seedlen]
         temp = int.from_bytes(temp, "big") ^ int.from_bytes(seed_material, "big")
@@ -52,7 +52,7 @@ class SM4_RNG:
         self.Key = temp[: self.keylen]
         self.V = temp[-self.blocklen :]
 
-    def SM4_df(self, input_string: bytes, number_of_bits_to_return: int):
+    def SM4_df(self, input_string: bytes, number_of_bits_to_return: int) -> bytes:
         L = len(input_string)
         N = number_of_bits_to_return
         S = L.to_bytes(4, "big") + N.to_bytes(4, "big") + input_string + b"\x80"
@@ -78,11 +78,11 @@ class SM4_RNG:
         requested_bits = tmp[:number_of_bits_to_return]
         return requested_bits
 
-    def CBC_MAC(self, Key, data_to_MAC):
+    def CBC_MAC(self, Key: bytes, data_to_MAC: bytes) -> bytes:
         self.sm4.set_key(Key, SM4_ENCRYPT)
         chaining_value = b"\x00" * self.outlen
-        n = len(data_to_MAC) / self.outlen
-        for i in range(int(n)):
+        n = len(data_to_MAC) // self.outlen
+        for i in range(n):
             input_block = int.from_bytes(chaining_value, "big") ^ int.from_bytes(
                 data_to_MAC[i * self.outlen : (i + 1) * self.outlen], "big"
             )
@@ -93,7 +93,7 @@ class SM4_RNG:
         output_block = chaining_value
         return output_block
 
-    def SM4_RNG_Reseed(self, additional_input: bytes):
+    def SM4_RNG_Reseed(self, additional_input: bytes) -> None:
         self.min_entropy = self.min_entropy_input_length
         self.entropy_input = secrets.token_bytes(self.min_entropy)
         self.seed_material = self.entropy_input + additional_input
@@ -102,8 +102,8 @@ class SM4_RNG:
         self.reseed_counter = 1
         self.last_reseed_time = int(time.time())
 
-    def SM4_RNG_Generate(self, requested_number_of_bits, additional_input: bytes = b""):
-        length = int(requested_number_of_bits / 8)
+    def SM4_RNG_Generate(self, requested_number_of_bits:int, additional_input: bytes = b"")->bytes:
+        length = requested_number_of_bits // 8
         returned_bits = b""
         if (
             self.reseed_counter > self.reseed_interval_in_counter
@@ -117,8 +117,8 @@ class SM4_RNG:
             additional_input = b"\x00" * self.seedlen
         self.sm4.set_key(self.Key, SM4_ENCRYPT)
         while len(returned_bits) < length:
-            self.V = int.from_bytes(self.V, "big") + 1 % (1 << self.blocklen)
-            self.V = self.V.to_bytes(self.blocklen, "big")
+            V_int = int.from_bytes(self.V, "big") + 1 % (1 << self.blocklen)
+            self.V = V_int.to_bytes(self.blocklen, "big")
             output_block = self.sm4.crypt_ecb(self.V)
             returned_bits = returned_bits + output_block
         self.SM4_RNG_Update(additional_input, self.Key, self.V)