13:65
  #   ˆl–ß=¿J	¥4Ò‚ D Eq¶î21hßÂ„^}ßÁÄ .y    #
#  AllOrNothing.py : all-or-nothing package transformations
#
# Part of the Python Cryptography Toolkit
#
# Written by Andrew M. Kuchling and others
#
# ===================================================================
# The contents of this file are dedicated to the public domain.  To
# the extent that dedication to the public domain is not available,
# everyone is granted a worldwide, perpetual, royalty-free,
# non-exclusive license to exercise all rights associated with the
# contents of this file for any purpose whatsoever.
# No rights are reserved.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# ===================================================================

"""This file implements all-or-nothing package transformations.

An all-or-nothing package transformation is one in which some text is
transformed into message blocks, such that all blocks must be obtained before
the reverse transformation can be applied.  Thus, if any blocks are corrupted
or lost, the original message cannot be reproduced.

An all-or-nothing package transformation is not encryption, although a block
cipher algorithm is used.  The encryption key is randomly generated and is
extractable from the message blocks.

This class implements the All-Or-Nothing package transformation algorithm
described in:

Ronald L. Rivest.  "All-Or-Nothing Encryption and The Package Transform"
http://theory.lcs.mit.edu/~rivest/fusion.pdf

"""

__revision__ = "$Id$"

import operator
import sys
from Crypto.Util.number import bytes_to_long, long_to_bytes
from Crypto.Util.py3compat import *

def isInt(x):
    test = 0
    try:
        test += x
    except TypeError:
        return 0
    return 1

class AllOrNothing:
    """Class implementing the All-or-Nothing package transform.

    Methods for subclassing:

        _inventkey(key_size):
            Returns a randomly generated key.  Subclasses can use this to
            implement better random key generating algorithms.  The default
            algorithm is probably not very cryptographically secure.

    """

    def __init__(self, ciphermodule, mode=None, IV=None):
        """AllOrNothing(ciphermodule, mode=None, IV=None)

        ciphermodule is a module implementing the cipher algorithm to
        use.  It must provide the PEP272 interface.

        Note that the encryption key is randomly generated
        automatically when needed.  Optional arguments mode and IV are
        passed directly through to the ciphermodule.new() method; they
        are the feedback mode and initialization vector to use.  All
        three arguments must be the same for the object used to create
        the digest, and to undigest'ify the message blocks.
        """

        self.__ciphermodule = ciphermodule
        self.__mode = mode
        self.__IV = IV
        self.__key_size = ciphermodule.key_size
        if not isInt(self.__key_size) or self.__key_size==0:
            self.__key_size = 16

    __K0digit = bchr(0x69)

    def digest(self, text):
        """digest(text:string) : [string]

        Perform the All-or-Nothing package transform on the given
        string.  Output is a list of message blocks describing the
        transformed text, where each block is a string of bit length equal
        to the ciphermodule's block_size.
        """

        # generate a random session key and K0, the key used to encrypt the
        # hash blocks.  Rivest calls this a fixed, publically-known encryption
        # key, but says nothing about the security implications of this key or
        # how to choose it.
        key = self._inventkey(self