Finished set 1 challenge 2

diff --git a/cryptopals-python/cryptopals.py b/cryptopals-python/cryptopals.py
index 8752786..d2eacf5 100644 (file)
--- a/cryptopals-python/cryptopals.py
+++ b/cryptopals-python/cryptopals.py
@@ -2,7 +2,14 @@ import codecs
 import unittest
 
 def base64_from_hex(_hex):
-    return codecs.encode(codecs.decode(_hex, 'hex'), 'base64').decode('utf-8')
+    return codecs.encode(bytes.fromhex(_hex), 'base64').decode('utf-8')
+
+def hex_xor(hex0, hex1):
+    assert len(hex0) == len(hex1)
+    bytes0 = bytes.fromhex(hex0)
+    bytes1 = bytes.fromhex(hex1)
+    xored_bytes = bytes(byte0 ^ byte1 for byte0, byte1 in zip(bytes0, bytes1))
+    return codecs.encode(xored_bytes, 'hex').decode('utf-8')
 
 class Set1Challenge1Tests(unittest.TestCase):
     def test_converts_hex_to_base64(self):
@@ -10,5 +17,15 @@ class Set1Challenge1Tests(unittest.TestCase):
         actual = base64_from_hex('49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d')
         self.assertEqual(expected, actual)
 
+class Set1Challenge2Tests(unittest.TestCase):
+    def test_xors_hex_strings(self):
+        hex0 = '1c0111001f010100061a024b53535009181c'
+        hex1 = '686974207468652062756c6c277320657965'
+
+        expected = '746865206b696420646f6e277420706c6179'
+        actual = hex_xor(hex0, hex1)
+
+        self.assertEqual(expected, actual)
+
 if __name__ == '__main__':
     unittest.main()