diff --git a/README.rst b/README.rst
index aa5a8290..10ea7ee9 100755
--- a/README.rst
+++ b/README.rst
@@ -127,6 +127,11 @@ There you'll find a list of all the methods, types and available constructors.
 
 More examples are also available under the ``telethon_examples/`` folder.
 
+If you're using Telethon under ARM, you may want to install ``sympy`` through
+``pip`` for a substantial speed-up when generating the keys required to
+connect to Telegram (you can of course do this on desktop too). See
+`issue #199 <https://github.com/LonamiWebs/Telethon/issues/199>`_ for more.
+
 Common errors
 -------------
 
diff --git a/telethon/crypto/aes.py b/telethon/crypto/aes.py
index c455c2b6..9a4459df 100644
--- a/telethon/crypto/aes.py
+++ b/telethon/crypto/aes.py
@@ -5,7 +5,9 @@ import pyaes
 class AES:
     @staticmethod
     def decrypt_ige(cipher_text, key, iv):
-        """Decrypts the given text in 16-bytes blocks by using the given key and 32-bytes initialization vector"""
+        """Decrypts the given text in 16-bytes blocks by using the
+           given key and 32-bytes initialization vector
+        """
         iv1 = iv[:len(iv) // 2]
         iv2 = iv[len(iv) // 2:]
 
@@ -17,8 +19,8 @@ class AES:
         cipher_text_block = [0] * 16
         for block_index in range(blocks_count):
             for i in range(16):
-                cipher_text_block[i] = cipher_text[block_index * 16 + i] ^ iv2[
-                    i]
+                cipher_text_block[i] = \
+                    cipher_text[block_index * 16 + i] ^ iv2[i]
 
             plain_text_block = aes.decrypt(cipher_text_block)
 
@@ -26,17 +28,19 @@ class AES:
                 plain_text_block[i] ^= iv1[i]
 
             iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
-            iv2 = plain_text_block[:]
+            iv2 = plain_text_block
 
-            plain_text.extend(plain_text_block[:])
+            plain_text.extend(plain_text_block)
 
         return bytes(plain_text)
 
     @staticmethod
     def encrypt_ige(plain_text, key, iv):
-        """Encrypts the given text in 16-bytes blocks by using the given key and 32-bytes initialization vector"""
+        """Encrypts the given text in 16-bytes blocks by using the
+           given key and 32-bytes initialization vector
+        """
 
-        # Add random padding if and only if it's not evenly divisible by 16 already
+        # Add random padding iff it's not evenly divisible by 16 already
         if len(plain_text) % 16 != 0:
             padding_count = 16 - len(plain_text) % 16
             plain_text += os.urandom(padding_count)
@@ -50,8 +54,9 @@ class AES:
         blocks_count = len(plain_text) // 16
 
         for block_index in range(blocks_count):
-            plain_text_block = list(plain_text[block_index * 16:block_index *
-                                               16 + 16])
+            plain_text_block = list(
+                plain_text[block_index * 16:block_index * 16 + 16]
+            )
             for i in range(16):
                 plain_text_block[i] ^= iv1[i]
 
@@ -60,9 +65,9 @@ class AES:
             for i in range(16):
                 cipher_text_block[i] ^= iv2[i]
 
-            iv1 = cipher_text_block[:]
+            iv1 = cipher_text_block
             iv2 = plain_text[block_index * 16:block_index * 16 + 16]
 
-            cipher_text.extend(cipher_text_block[:])
+            cipher_text.extend(cipher_text_block)
 
         return bytes(cipher_text)
diff --git a/telethon/crypto/factorization.py b/telethon/crypto/factorization.py
index e6601f5a..12a03af3 100644
--- a/telethon/crypto/factorization.py
+++ b/telethon/crypto/factorization.py
@@ -1,4 +1,8 @@
 from random import randint
+try:
+    import sympy.ntheory
+except ImportError:
+    sympy = None
 
 
 class Factorization:
@@ -58,5 +62,8 @@ class Factorization:
     @staticmethod
     def factorize(pq):
         """Factorizes the given number and returns both the divisor and the number divided by the divisor"""
-        divisor = Factorization.find_small_multiplier_lopatin(pq)
-        return divisor, pq // divisor
+        if sympy:
+            return tuple(sympy.ntheory.factorint(pq).keys())
+        else:
+            divisor = Factorization.find_small_multiplier_lopatin(pq)
+            return divisor, pq // divisor