+++ /dev/null
-from enum import Enum
-import multiprocessing
-import itertools
-
-from utilities import *
-from language_models import *
-from column_transposition import transpositions
-
-from logger import logger
-
-# Where each piece of text ends up in the AMSCO transpositon cipher.
-# 'index' shows where the slice appears in the plaintext, with the slice
-# from 'start' to 'end'
-AmscoSlice = collections.namedtuple('AmscoSlice', ['index', 'start', 'end'])
-
-class AmscoFillStyle(Enum):
- continuous = 1
- same_each_row = 2
- reverse_each_row = 3
-
-def amsco_transposition_positions(message, keyword,
- fillpattern=(1, 2),
- fillstyle=AmscoFillStyle.continuous,
- fillcolumnwise=False,
- emptycolumnwise=True):
- """Creates the grid for the AMSCO transposition cipher. Each element in the
- grid shows the index of that slice and the start and end positions of the
- plaintext that go to make it up.
-
- >>> amsco_transposition_positions(string.ascii_lowercase, 'freddy', \
- fillpattern=(1, 2)) # doctest: +NORMALIZE_WHITESPACE
- [[AmscoSlice(index=3, start=4, end=6),
- AmscoSlice(index=2, start=3, end=4),
- AmscoSlice(index=0, start=0, end=1),
- AmscoSlice(index=1, start=1, end=3),
- AmscoSlice(index=4, start=6, end=7)],
- [AmscoSlice(index=8, start=12, end=13),
- AmscoSlice(index=7, start=10, end=12),
- AmscoSlice(index=5, start=7, end=9),
- AmscoSlice(index=6, start=9, end=10),
- AmscoSlice(index=9, start=13, end=15)],
- [AmscoSlice(index=13, start=19, end=21),
- AmscoSlice(index=12, start=18, end=19),
- AmscoSlice(index=10, start=15, end=16),
- AmscoSlice(index=11, start=16, end=18),
- AmscoSlice(index=14, start=21, end=22)],
- [AmscoSlice(index=18, start=27, end=28),
- AmscoSlice(index=17, start=25, end=27),
- AmscoSlice(index=15, start=22, end=24),
- AmscoSlice(index=16, start=24, end=25),
- AmscoSlice(index=19, start=28, end=30)]]
- """
- transpositions = transpositions_of(keyword)
- fill_iterator = itertools.cycle(fillpattern)
- indices = itertools.count()
- message_length = len(message)
-
- current_position = 0
- grid = []
- current_fillpattern = fillpattern
- while current_position < message_length:
- row = []
- if fillstyle == AmscoFillStyle.same_each_row:
- fill_iterator = itertools.cycle(fillpattern)
- if fillstyle == AmscoFillStyle.reverse_each_row:
- fill_iterator = itertools.cycle(current_fillpattern)
- for _ in range(len(transpositions)):
- index = next(indices)
- gap = next(fill_iterator)
- row += [AmscoSlice(index, current_position, current_position + gap)]
- current_position += gap
- grid += [row]
- if fillstyle == AmscoFillStyle.reverse_each_row:
- current_fillpattern = list(reversed(current_fillpattern))
- return [transpose(r, transpositions) for r in grid]
-
-def amsco_transposition_encipher(message, keyword,
- fillpattern=(1,2), fillstyle=AmscoFillStyle.reverse_each_row):
- """AMSCO transposition encipher.
-
- >>> amsco_transposition_encipher('hellothere', 'abc', fillpattern=(1, 2))
- 'hoteelhler'
- >>> amsco_transposition_encipher('hellothere', 'abc', fillpattern=(2, 1))
- 'hetelhelor'
- >>> amsco_transposition_encipher('hellothere', 'acb', fillpattern=(1, 2))
- 'hotelerelh'
- >>> amsco_transposition_encipher('hellothere', 'acb', fillpattern=(2, 1))
- 'hetelorlhe'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'encode')
- 'etecstthhomoerereenisxip'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2))
- 'hetcsoeisterereipexthomn'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
- 'hecsoisttererteipexhomen'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(2, 1))
- 'heecisoosttrrtepeixhemen'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2))
- 'hxtomephescieretoeisnter'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
- 'hxomeiphscerettoisenteer'
- """
- grid = amsco_transposition_positions(message, keyword,
- fillpattern=fillpattern, fillstyle=fillstyle)
- ct_as_grid = [[message[s.start:s.end] for s in r] for r in grid]
- return combine_every_nth(ct_as_grid)
-
-
-def amsco_transposition_decipher(message, keyword,
- fillpattern=(1,2), fillstyle=AmscoFillStyle.reverse_each_row):
- """AMSCO transposition decipher
-
- >>> amsco_transposition_decipher('hoteelhler', 'abc', fillpattern=(1, 2))
- 'hellothere'
- >>> amsco_transposition_decipher('hetelhelor', 'abc', fillpattern=(2, 1))
- 'hellothere'
- >>> amsco_transposition_decipher('hotelerelh', 'acb', fillpattern=(1, 2))
- 'hellothere'
- >>> amsco_transposition_decipher('hetelorlhe', 'acb', fillpattern=(2, 1))
- 'hellothere'
- >>> amsco_transposition_decipher('etecstthhomoerereenisxip', 'encode')
- 'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hetcsoeisterereipexthomn', 'cipher', fillpattern=(1, 2))
- 'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hecsoisttererteipexhomen', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
- 'hereissometexttoencipher'
- >>> amsco_transposition_decipher('heecisoosttrrtepeixhemen', 'cipher', fillpattern=(2, 1))
- 'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hxtomephescieretoeisnter', 'cipher', fillpattern=(1, 3, 2))
- 'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hxomeiphscerettoisenteer', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
- 'hereissometexttoencipher'
- """
-
- grid = amsco_transposition_positions(message, keyword,
- fillpattern=fillpattern, fillstyle=fillstyle)
- transposed_sections = [s for c in [l for l in zip(*grid)] for s in c]
- plaintext_list = [''] * len(transposed_sections)
- current_pos = 0
- for slice in transposed_sections:
- plaintext_list[slice.index] = message[current_pos:current_pos-slice.start+slice.end][:len(message[slice.start:slice.end])]
- current_pos += len(message[slice.start:slice.end])
- return cat(plaintext_list)
-
-
-def amsco_break(message, translist=transpositions, patterns = [(1, 2), (2, 1)],
- fillstyles = [AmscoFillStyle.continuous,
- AmscoFillStyle.same_each_row,
- AmscoFillStyle.reverse_each_row],
- fitness=Pbigrams,
- chunksize=500):
- """Breaks an AMSCO transposition cipher using a dictionary and
- n-gram frequency analysis
-
- >>> amsco_break(amsco_transposition_encipher(sanitise( \
- "It is a truth universally acknowledged, that a single man in \
- possession of a good fortune, must be in want of a wife. However \
- little known the feelings or views of such a man may be on his \
- first entering a neighbourhood, this truth is so well fixed in \
- the minds of the surrounding families, that he is considered the \
- rightful property of some one or other of their daughters."), \
- 'encipher'), \
- translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
- (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
- (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
- patterns=[(1, 2)]) # doctest: +ELLIPSIS
- (((2, 0, 5, 3, 1, 4, 6), (1, 2), <AmscoFillStyle.continuous: 1>), -709.4646722...)
- >>> amsco_break(amsco_transposition_encipher(sanitise( \
- "It is a truth universally acknowledged, that a single man in \
- possession of a good fortune, must be in want of a wife. However \
- little known the feelings or views of such a man may be on his \
- first entering a neighbourhood, this truth is so well fixed in \
- the minds of the surrounding families, that he is considered the \
- rightful property of some one or other of their daughters."), \
- 'encipher', fillpattern=(2, 1)), \
- translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
- (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
- (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
- patterns=[(1, 2), (2, 1)], fitness=Ptrigrams) # doctest: +ELLIPSIS
- (((2, 0, 5, 3, 1, 4, 6), (2, 1), <AmscoFillStyle.continuous: 1>), -997.0129085...)
- """
- with multiprocessing.Pool() as pool:
- helper_args = [(message, trans, pattern, fillstyle, fitness)
- for trans in translist
- for pattern in patterns
- for fillstyle in fillstyles]
- # Gotcha: the helper function here needs to be defined at the top level
- # (limitation of Pool.starmap)
- breaks = pool.starmap(amsco_break_worker, helper_args, chunksize)
- return max(breaks, key=lambda k: k[1])
-
-def amsco_break_worker(message, transposition,
- pattern, fillstyle, fitness):
- plaintext = amsco_transposition_decipher(message, transposition,
- fillpattern=pattern, fillstyle=fillstyle)
- fit = fitness(sanitise(plaintext))
- logger.debug('AMSCO transposition break attempt using key {0} and pattern'
- '{1} ({2}) gives fit of {3} and decrypt starting: '
- '{4}'.format(
- transposition, pattern, fillstyle, fit,
- sanitise(plaintext)[:50]))
- return (transposition, pattern, fillstyle), fit
-
-if __name__ == "__main__":
- import doctest
\ No newline at end of file
projects / cipher-tools.git / blobdiff