+"""Enciphering and deciphering using the [Amsco cipher](http://ericbrandel.com/2016/10/09/the-amsco-cipher/).
+Also attempts to break messages that use an Amsco cipher.
+
+The Amsco cipher is a column transpositoin cipher. The plaintext is laid out,
+row by row, into columns. However, different numbers of letters are laid out
+in each cell, typically in a 1-2 pattern.
+
+It's clearer with an example. Consider we're using the keyword "perceptive",
+which turns into "perctiv". The text ""It is a truth universally
+acknowledged, that a single man in, possession of a good fortune, must be in
+want of a wife." is laid out in seven columns like this:
+
+ p e r c t i v
+ --------------------
+ i ti s at r ut h
+ un i ve r sa l ly
+ a ck n ow l ed g
+ ed t ha t as i ng
+ l em a ni n po s
+ se s si o no f ag
+ o od f or t un e
+ mu s tb e in w an
+ t of a wi f e
+
+The ciphertext is read out in columns, according to the order of the keyword.
+In this example, the "c" column is read first, then the "e" column, and so on.
+That gives the ciphertext of "atrowtnioorewi tiicktemsodsof utledipofunwe
+iunaedlseomut svenhaasiftba rsalasnnotinf hlygngsagean".
+"""
+
from enum import Enum
import multiprocessing
import itertools
from szyfrow.support.utilities import *
from szyfrow.support.language_models import *
-from szyfrow.column_transposition import transpositions, transpositions_of
-# 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'
+__pdoc__ = {}
+
AmscoSlice = collections.namedtuple('AmscoSlice', ['index', 'start', 'end'])
+__pdoc__['AmscoSlice'] = """Where each piece of plainatext ends up in the AMSCO
+transpositon cipher."""
+__pdoc__['AmscoSlice.index'] = """Where the slice appears in the plaintext"""
+__pdoc__['AmscoSlice.start'] = """Where the slice starts in the plaintext"""
+__pdoc__['AmscoSlice.end'] = """Where the slice ends in the plaintext"""
class AmscoFillStyle(Enum):
+ """Different methods of filling the grid.
+ * `continuous`: continue the fillpattern unbroken by row boundaries
+ * `same_each_row`: each row has the same fillpattern
+ * `reverse_each_row`: each row has the reversed fillpattern to the row above
+ """
continuous = 1
same_each_row = 2
reverse_each_row = 3
-def amsco_transposition_positions(message, keyword,
+def amsco_positions(message, keyword,
fillpattern=(1, 2),
fillstyle=AmscoFillStyle.continuous,
fillcolumnwise=False,
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', \
+ >>> amsco_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),
current_fillpattern = list(reversed(current_fillpattern))
return [transpose(r, transpositions) for r in grid]
-def amsco_transposition_encipher(message, keyword,
+def amsco_encipher(message, keyword,
fillpattern=(1,2), fillstyle=AmscoFillStyle.reverse_each_row):
"""AMSCO transposition encipher.
- >>> amsco_transposition_encipher('hellothere', 'abc', fillpattern=(1, 2))
+ >>> amsco_encipher('hellothere', 'abc', fillpattern=(1, 2))
'hoteelhler'
- >>> amsco_transposition_encipher('hellothere', 'abc', fillpattern=(2, 1))
+ >>> amsco_encipher('hellothere', 'abc', fillpattern=(2, 1))
'hetelhelor'
- >>> amsco_transposition_encipher('hellothere', 'acb', fillpattern=(1, 2))
+ >>> amsco_encipher('hellothere', 'acb', fillpattern=(1, 2))
'hotelerelh'
- >>> amsco_transposition_encipher('hellothere', 'acb', fillpattern=(2, 1))
+ >>> amsco_encipher('hellothere', 'acb', fillpattern=(2, 1))
'hetelorlhe'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'encode')
+ >>> amsco_encipher('hereissometexttoencipher', 'encode')
'etecstthhomoerereenisxip'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2))
+ >>> amsco_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2))
'hetcsoeisterereipexthomn'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
+ >>> amsco_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
'hecsoisttererteipexhomen'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(2, 1))
+ >>> amsco_encipher('hereissometexttoencipher', 'cipher', fillpattern=(2, 1))
'heecisoosttrrtepeixhemen'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2))
+ >>> amsco_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2))
'hxtomephescieretoeisnter'
- >>> amsco_transposition_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
+ >>> amsco_encipher('hereissometexttoencipher', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
'hxomeiphscerettoisenteer'
"""
- grid = amsco_transposition_positions(message, keyword,
+ grid = amsco_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,
+def amsco_decipher(message, keyword,
fillpattern=(1,2), fillstyle=AmscoFillStyle.reverse_each_row):
"""AMSCO transposition decipher
- >>> amsco_transposition_decipher('hoteelhler', 'abc', fillpattern=(1, 2))
+ >>> amsco_decipher('hoteelhler', 'abc', fillpattern=(1, 2))
'hellothere'
- >>> amsco_transposition_decipher('hetelhelor', 'abc', fillpattern=(2, 1))
+ >>> amsco_decipher('hetelhelor', 'abc', fillpattern=(2, 1))
'hellothere'
- >>> amsco_transposition_decipher('hotelerelh', 'acb', fillpattern=(1, 2))
+ >>> amsco_decipher('hotelerelh', 'acb', fillpattern=(1, 2))
'hellothere'
- >>> amsco_transposition_decipher('hetelorlhe', 'acb', fillpattern=(2, 1))
+ >>> amsco_decipher('hetelorlhe', 'acb', fillpattern=(2, 1))
'hellothere'
- >>> amsco_transposition_decipher('etecstthhomoerereenisxip', 'encode')
+ >>> amsco_decipher('etecstthhomoerereenisxip', 'encode')
'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hetcsoeisterereipexthomn', 'cipher', fillpattern=(1, 2))
+ >>> amsco_decipher('hetcsoeisterereipexthomn', 'cipher', fillpattern=(1, 2))
'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hecsoisttererteipexhomen', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
+ >>> amsco_decipher('hecsoisttererteipexhomen', 'cipher', fillpattern=(1, 2), fillstyle=AmscoFillStyle.continuous)
'hereissometexttoencipher'
- >>> amsco_transposition_decipher('heecisoosttrrtepeixhemen', 'cipher', fillpattern=(2, 1))
+ >>> amsco_decipher('heecisoosttrrtepeixhemen', 'cipher', fillpattern=(2, 1))
'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hxtomephescieretoeisnter', 'cipher', fillpattern=(1, 3, 2))
+ >>> amsco_decipher('hxtomephescieretoeisnter', 'cipher', fillpattern=(1, 3, 2))
'hereissometexttoencipher'
- >>> amsco_transposition_decipher('hxomeiphscerettoisenteer', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
+ >>> amsco_decipher('hxomeiphscerettoisenteer', 'cipher', fillpattern=(1, 3, 2), fillstyle=AmscoFillStyle.continuous)
'hereissometexttoencipher'
"""
- grid = amsco_transposition_positions(message, keyword,
+ grid = amsco_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)
return cat(plaintext_list)
-def amsco_break(message, translist=transpositions, patterns = [(1, 2), (2, 1)],
+def amsco_break(message, translist=None, 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
+ n-gram frequency analysis.
+
+ If `translist` is not specified, use
+ [`szyfrow.support.langauge_models.transpositions`](support/language_models.html#szyfrow.support.language_models.transpositions).
- >>> amsco_break(amsco_transposition_encipher(sanitise( \
+ >>> amsco_break(amsco_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 \
(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( \
+ >>> amsco_break(amsco_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 \
patterns=[(1, 2), (2, 1)], fitness=Ptrigrams) # doctest: +ELLIPSIS
(((2, 0, 5, 3, 1, 4, 6), (2, 1), <AmscoFillStyle.continuous: 1>), -997.0129085...)
"""
+ if translist is None:
+ translist = transpositions
+
with multiprocessing.Pool() as pool:
helper_args = [(message, trans, pattern, fillstyle, fitness)
for trans in translist
def amsco_break_worker(message, transposition,
pattern, fillstyle, fitness):
- plaintext = amsco_transposition_decipher(message, transposition,
+ plaintext = amsco_decipher(message, transposition,
fillpattern=pattern, fillstyle=fillstyle)
fit = fitness(sanitise(plaintext))
return (transposition, pattern, fillstyle), fit
projects / szyfrow.git / blobdiff