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Diffstat (limited to 'frozen_deps/Crypto/Random/Fortuna/FortunaGenerator.py')
| -rw-r--r-- | frozen_deps/Crypto/Random/Fortuna/FortunaGenerator.py | 132 |
1 files changed, 0 insertions, 132 deletions
diff --git a/frozen_deps/Crypto/Random/Fortuna/FortunaGenerator.py b/frozen_deps/Crypto/Random/Fortuna/FortunaGenerator.py deleted file mode 100644 index 489c81e..0000000 --- a/frozen_deps/Crypto/Random/Fortuna/FortunaGenerator.py +++ /dev/null @@ -1,132 +0,0 @@ -# -*- coding: ascii -*- -# -# FortunaGenerator.py : Fortuna's internal PRNG -# -# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net> -# -# =================================================================== -# 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. -# =================================================================== - -__revision__ = "$Id$" - -import sys -if sys.version_info[0] is 2 and sys.version_info[1] is 1: - from Crypto.Util.py21compat import * -from Crypto.Util.py3compat import * - -import struct - -from Crypto.Util.number import ceil_shift, exact_log2, exact_div -from Crypto.Util import Counter -from Crypto.Cipher import AES - -from . import SHAd256 - -class AESGenerator(object): - """The Fortuna "generator" - - This is used internally by the Fortuna PRNG to generate arbitrary amounts - of pseudorandom data from a smaller amount of seed data. - - The output is generated by running AES-256 in counter mode and re-keying - after every mebibyte (2**16 blocks) of output. - """ - - block_size = AES.block_size # output block size in octets (128 bits) - key_size = 32 # key size in octets (256 bits) - - # Because of the birthday paradox, we expect to find approximately one - # collision for every 2**64 blocks of output from a real random source. - # However, this code generates pseudorandom data by running AES in - # counter mode, so there will be no collisions until the counter - # (theoretically) wraps around at 2**128 blocks. Thus, in order to prevent - # Fortuna's pseudorandom output from deviating perceptibly from a true - # random source, Ferguson and Schneier specify a limit of 2**16 blocks - # without rekeying. - max_blocks_per_request = 2**16 # Allow no more than this number of blocks per _pseudo_random_data request - - _four_kiblocks_of_zeros = b("\0") * block_size * 4096 - - def __init__(self): - self.counter = Counter.new(nbits=self.block_size*8, initial_value=0, little_endian=True) - self.key = None - - # Set some helper constants - self.block_size_shift = exact_log2(self.block_size) - assert (1 << self.block_size_shift) == self.block_size - - self.blocks_per_key = exact_div(self.key_size, self.block_size) - assert self.key_size == self.blocks_per_key * self.block_size - - self.max_bytes_per_request = self.max_blocks_per_request * self.block_size - - def reseed(self, seed): - if self.key is None: - self.key = b("\0") * self.key_size - - self._set_key(SHAd256.new(self.key + seed).digest()) - self.counter() # increment counter - assert len(self.key) == self.key_size - - def pseudo_random_data(self, bytes): - assert bytes >= 0 - - num_full_blocks = bytes >> 20 - remainder = bytes & ((1<<20)-1) - - retval = [] - for i in range(num_full_blocks): - retval.append(self._pseudo_random_data(1<<20)) - retval.append(self._pseudo_random_data(remainder)) - - return b("").join(retval) - - def _set_key(self, key): - self.key = key - self._cipher = AES.new(key, AES.MODE_CTR, counter=self.counter) - - def _pseudo_random_data(self, bytes): - if not (0 <= bytes <= self.max_bytes_per_request): - raise AssertionError("You cannot ask for more than 1 MiB of data per request") - - num_blocks = ceil_shift(bytes, self.block_size_shift) # num_blocks = ceil(bytes / self.block_size) - - # Compute the output - retval = self._generate_blocks(num_blocks)[:bytes] - - # Switch to a new key to avoid later compromises of this output (i.e. - # state compromise extension attacks) - self._set_key(self._generate_blocks(self.blocks_per_key)) - - assert len(retval) == bytes - assert len(self.key) == self.key_size - - return retval - - def _generate_blocks(self, num_blocks): - if self.key is None: - raise AssertionError("generator must be seeded before use") - assert 0 <= num_blocks <= self.max_blocks_per_request - retval = [] - for i in range(num_blocks >> 12): # xrange(num_blocks / 4096) - retval.append(self._cipher.encrypt(self._four_kiblocks_of_zeros)) - remaining_bytes = (num_blocks & 4095) << self.block_size_shift # (num_blocks % 4095) * self.block_size - retval.append(self._cipher.encrypt(self._four_kiblocks_of_zeros[:remaining_bytes])) - return b("").join(retval) - -# vim:set ts=4 sw=4 sts=4 expandtab: |