Implementation of bitwise XOR function for bytes object (#72)

1 files changed, 21 insertions, 0 deletions

diff --git a/rsa/_compat.py b/rsa/_compat.py
index 1e51368..38bab08 100644
--- a/rsa/_compat.py
+++ b/rsa/_compat.py
@@ -99,6 +99,27 @@ def byte(num):
     return pack("B", num)
 
 
+def xor_bytes(b1, b2):
+    """
+    Returns the bitwise XOR result between two bytes objects, b1 ^ b2.
+
+    Bitwise XOR operation is commutative, so order of parameters doesn't
+    generate different results. If parameters have different length, extra
+    length of the largest one is ignored.
+
+    :param b1:
+        First bytes object.
+    :param b2:
+        Second bytes object.
+    :returns:
+        Bytes object, result of XOR operation.
+    """
+    if PY2:
+        return ''.join(byte(ord(x) ^ ord(y)) for x, y in zip(b1, b2))
+
+    return bytes(x ^ y for x, y in zip(b1, b2))
+
+
 def get_word_alignment(num, force_arch=64,
                        _machine_word_size=MACHINE_WORD_SIZE):
     """