cryptopan.py

#!/usr/bin/env ipython3

#   pycryptopan - a python module implementing the CryptoPAn algorithm
#   Copyright (C) 2013 - the CONFINE project

#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Lesser General Public License as
#   published by the Free Software Foundation, either version 3 of the
#   License, or (at your option) any later version.

#   This program 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 Lesser General Public License
#   along with this program.  If not, see <http://www.gnu.org/licenses/>.

from functools import reduce
# from pycrypto module
from Crypto.Cipher.AES import new as AES
# from Crypto import Random


class CryptoPanError(Exception):
    def __init__(self, value):
        self.value=value

    def __str__(self):
        return repr(self.value)


class CryptoPan():
    def __init__(self, key):
        if len(key)!=32:
            raise CryptoPanError("Key must be a 32 byte long string")
        self.aes=AES(key[0:16])
        self.pad=self.aes.encrypt(key[16:32])

        f4=self.pad[0:4]
        # Python 2 requires explicit conversion to ints
        if isinstance(f4, str):
            f4=[ord(x) for x in f4]

        f4bp=self.toint(f4)
        self.masks=[(mask, f4bp & (~ mask)) for mask in (0xFFFFFFFF >> (32 - p) << (32 - p) for p in range(0, 32))]

    def toint(self, array):
        return array[0] << 24 | array[1] <<16 | array[2] << 8 | array[3]

    def toarray(self, n):
        for i in range(3, -1, -1):
            yield (n >> (i * 8)) & 0xFF

    def anonymize(self, ip):
        result=0
        address=[int(x) for x in ip.split(".")]
        if len(address)!=4:
            raise CryptoPanError("Invalid IPv4 Address")

        address=self.toint(address)

        def calc(a):
            """ calculate the first bit for Crypto-PAN"""
            a_array = self.toarray(a)

            # Python 2 requires converting ints to chars one at a time
            if isinstance(self.pad, str):
                inp="".join((chr(x) for x in a_array))
            else:
                inp=bytes(a_array)

            inp+=self.pad[4:]
            rin_output=self.aes.encrypt(inp)

            out=rin_output[0]
            # Python 2 requires explicit conversion to int
            if isinstance(out, str):
                out=ord(out)

            return out >> 7

        addresses=((address & mask[0]) | mask[1] for mask in self.masks)
        result=reduce(lambda x, y: x << 1 | y, (calc(a) for a in addresses), 0)
        return ".".join(["%s" % x for x in self.toarray(result ^ address)])