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Diffstat (limited to 'combox/crypto.py')
-rw-r--r-- | combox/crypto.py | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/combox/crypto.py b/combox/crypto.py new file mode 100644 index 0000000..3f17cc0 --- /dev/null +++ b/combox/crypto.py @@ -0,0 +1,84 @@ +# 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 |