Added crypto.py: Contains function that encrypt data and decrypt ciphers using AES.

Functions defined: pad, encrypt, decrypt, encrypt_shards, decrypt_shards.

Also added: tests/test_crypto.py

1 files changed, 84 insertions, 0 deletions

diff --git a/combox/crypto.py b/combox/crypto.py
new file mode 100644
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+++ b/combox/crypto.py
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+#    Copyright (C) 2014 Combox author(s). See AUTHORS.
+#
+#    This file is part of Combox.
+#
+#   Combox is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Combox is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#   General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with Combox (see COPYING).  If not, see
+#   <http://www.gnu.org/licenses/>.
+
+## Adapted from https://gist.github.com/sekondus/4322469
+
+import base64
+import os
+
+from Crypto.Cipher import AES
+
+BLOCK_SIZE = 32
+PAD_CHAR = '#'
+
+
+def pad(data):
+    """Pad data such that its length is a multiple of BLOCK_SIZE.
+    """
+
+    padding = (BLOCK_SIZE - (len(data) % BLOCK_SIZE)) * PAD_CHAR
+    data += padding
+
+    return data
+
+
+def encrypt(data, secret):
+    """Encrypt byestream and return cipher.
+    """
+    aes = AES.new(pad(secret))
+    cipher = base64.b64encode(aes.encrypt(pad(data)))
+    
+    return cipher
+
+
+def decrypt(cipher, secret):
+    """Decrypt cipher and return data.
+    """
+    aes = AES.new(pad(secret))
+    data = aes.decrypt(base64.b64decode(cipher)).rstrip(PAD_CHAR)
+
+    return data
+
+def encrypt_shards(shards, secret):
+    """Encrypt the shards of data and return a list of ciphers.
+
+    shards: list of shards (string, bytes).
+    secret: top secret passphrase
+    """
+
+    ciphers = []
+    for shard in shards:
+        cipher = encrypt(shard, secret)
+        ciphers.append(cipher)
+
+    return ciphers
+
+
+def decrypt_shards(ciphers, secret):
+    """Decrypt the ciphered shards and return a list of shards.
+
+    shards: list of ciphered shards.
+    secret: top secret passphrase
+    """
+
+    shards = []
+    for cipher in ciphers:
+        shard = decrypt(cipher, secret)
+        shards.append(shard)
+
+    return shards