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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
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