# /usr/bin/env python # coding=utf-8 # Copyright 2010 Jonathan Bowman # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or # implied. See the License for the specific language governing # permissions and limitations under the License. """Pure Python implementation of the Skein 512-bit hashing algorithm""" import array import binascii import os import struct from threefish import (add64, bigint, bytes2words, Threefish512, words, words2bytes, words_format, xrange, zero_bytes, zero_words) # An empty bytestring that behaves itself whether in Python 2 or 3 empty_bytes = array.array('B').tostring() class Skein512(object): """Skein 512-bit hashing algorithm The message to be hashed may be set as `msg` when initialized, or passed in later using the ``update`` method. Use `key` (a bytestring with arbitrary length) for MAC functionality. `block_type` will typically be "msg", but may also be one of: "key", "nonce", "cfg_final", or "out_final". These will affect the tweak value passed to the underlying Threefish block cipher. Again, if you don't know which one to choose, "msg" is probably what you want. Example: >>> Skein512("Hello, world!").hexdigest() '8449f597f1764274f8bf4a03ead22e0404ea2dc63c8737629e6e282303aebfd5dd96f07e21ae2e7a8b2bdfadd445bd1d71dfdd9745c95b0eb05dc01f289ad765' """ block_size = 64 block_bits = 512 block_type = {'key': 0, 'nonce': 0x5400000000000000, 'msg': 0x7000000000000000, 'cfg_final': 0xc400000000000000, 'out_final': 0xff00000000000000} def __init__(self, msg='', digest_bits=512, key=None, block_type='msg'): self.tf = Threefish512() if key: self.digest_bits = 512 self._start_new_type('key') self.update(key) self.tf.key = bytes2words(self.final(False)) self.digest_bits = digest_bits self.digest_size = (digest_bits + 7) >> 3 self._start_new_type('cfg_final') b = words2bytes((0x133414853,digest_bits,0,0,0,0,0,0)) self._process_block(b,32) self._start_new_type(block_type) if msg: self.update(msg) def _start_new_type(self, block_type): """Setup new tweak values and internal buffer. Primarily for internal use. """ self.buf = empty_bytes self.tf.tweak = words([0, self.block_type[block_type]]) def _process_block(self, block, byte_count_add): """Encrypt internal state using Threefish. Primarily for internal use. """ block_len = len(block) for i in xrange(0,block_len,64): w = bytes2words(block[i:i+64]) self.tf.tweak[0] = add64(self.tf.tweak[0], byte_count_add) self.tf.prepare_tweak() self.tf.prepare_key() self.tf.key = self.tf.encrypt_block(w) self.tf._feed_forward(self.tf.key, w) # set second tweak value to ~SKEIN_T1_FLAG_FIRST: self.tf.tweak[1] &= bigint(0xbfffffffffffffff) def update(self, msg): """Update internal state with new data to be hashed. `msg` is a bytestring, and should be a bytes object in Python 3 and up, or simply a string in Python 2.5 and 2.6. """ self.buf += msg buflen = len(self.buf) if buflen > 64: end = -(buflen % 64) or (buflen-64) data = self.buf[0:end] self.buf = self.buf[end:] try: self._process_block(data, 64) except: print(len(data)) print(binascii.b2a_hex(data)) def final(self, output=True): """Return hashed data as bytestring. `output` is primarily for internal use. It should only be False if you have a clear reason for doing so. This function can be called as either ``final`` or ``digest``. """ self.tf.tweak[1] |= bigint(0x8000000000000000) # SKEIN_T1_FLAG_FINAL buflen = len(self.buf) self.buf += zero_bytes[:64-buflen] self._process_block(self.buf, buflen) if not output: hash_val = words2bytes(self.tf.key) else: hash_val = empty_bytes self.buf = zero_bytes[:] key = self.tf.key[:] # temporary copy i=0 while i*64 < self.digest_size: self.buf = words_format[1].pack(i) + self.buf[8:] self.tf.tweak = [0, self.block_type['out_final']] self._process_block(self.buf, 8) n = self.digest_size - i*64 if n >= 64: n = 64 hash_val += words2bytes(self.tf.key)[0:n] self.tf.key = key i+=1 return hash_val digest = final def hexdigest(self): """Return a hexadecimal representation of the hashed data""" return binascii.b2a_hex(self.digest()) class Skein512Random(Skein512): """A Skein-based pseudo-random bytestring generator. If `seed` is unspecified, ``os.urandom`` will be used to provide the seed. In case you are using this as an iterator, rather than generating new data at each iteration, a pool of length `queue_size` is generated periodically. """ def __init__(self, seed=None, queue_size=512): Skein512.__init__(self, block_type='nonce') self.queue = [] self.queue_size = queue_size self.tf.key = zero_words[:] if not seed: seed = os.urandom(100) self.reseed(seed) def reseed(self, seed): """(Re)seed the generator.""" self.digest_size = 64 self.update(words2bytes(self.tf.key) + seed) self.tf.key = bytes2words(self.final()) def getbytes(self, request_bytes): """Return random bytestring of length `request_bytes`.""" self.digest_size = 64 + request_bytes self.update(words2bytes(self.tf.key)) output = self.final() self.tf.key = bytes2words(output[0:64]) return output[64:] def __iter__(self): return self def next(self): if not self.queue: self.queue = array.array('B', self.getbytes(self.queue_size)) return self.queue.pop() if __name__ == '__main__': print Skein512('123').hexdigest()