Started implementating encryption for fernet

1 files changed, 36 insertions, 0 deletions

diff --git a/cryptography/fernet.py b/cryptography/fernet.py
new file mode 100644
index 00000000..a0996afc
--- /dev/null
+++ b/cryptography/fernet.py
@@ -0,0 +1,36 @@
+import base64
+import os
+import struct
+import time
+
+from cryptography.hazmat.primitives import padding, hashes
+from cryptography.hazmat.primitives.hmac import HMAC
+from cryptography.hazmat.primitives.block import BlockCipher, ciphers, modes
+
+
+class Fernet(object):
+    def __init__(self, key):
+        super(Fernet, self).__init__()
+        self.signing_key = key[:16]
+        self.encryption_key = key[16:]
+
+    def encrypt(self, data):
+        current_time = int(time.time())
+        iv = os.urandom(16)
+        return self._encrypt_from_parts(data, current_time, iv)
+
+    def _encrypt_from_parts(self, data, current_time, iv):
+        padder = padding.PKCS7(ciphers.AES.block_size).padder()
+        padded_data = padder.update(data) + padder.finalize()
+        encryptor = BlockCipher(ciphers.AES(self.encryption_key), modes.CBC(iv)).encryptor()
+        ciphertext = encryptor.update(padded_data) + encryptor.finalize()
+
+        h = HMAC(self.signing_key, digestmod=hashes.SHA256)
+        h.update(b"\x80")
+        h.update(struct.pack(">Q", current_time))
+        h.update(iv)
+        h.update(ciphertext)
+        hmac = h.digest()
+        return base64.urlsafe_b64encode(
+            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext + hmac
+        )