Fix #19: Implemented blinding when decrypting.

This prevents side-channel (such as timing) attacks, see:
https://en.wikipedia.org/wiki/Blinding_%28cryptography%29

1 files changed, 30 insertions, 0 deletions

diff --git a/tests/test_key.py b/tests/test_key.py
new file mode 100644
index 0000000..df35335
--- /dev/null
+++ b/tests/test_key.py
@@ -0,0 +1,30 @@
+"""
+Some tests for the rsa/key.py file.
+"""
+
+
+import unittest
+
+import rsa.key
+import rsa.core
+
+
+class BlindingTest(unittest.TestCase):
+
+    def test_blinding(self):
+        """Test blinding and unblinding.
+
+        This is basically the doctest of the PrivateKey.blind method, but then
+        implemented as unittest to allow running on different Python versions.
+        """
+
+        pk = rsa.key.PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
+
+        message = 12345
+        encrypted = rsa.core.encrypt_int(message, pk.e, pk.n)
+
+        blinded = pk.blind(encrypted, 4134431)  # blind before decrypting
+        decrypted = rsa.core.decrypt_int(blinded, pk.d, pk.n)
+        unblinded = pk.unblind(decrypted, 4134431)
+
+        self.assertEqual(unblinded, message)