From: Neil Smith Date: Sun, 17 Nov 2013 23:22:45 +0000 (+0000) Subject: Column transposition written but untested X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=662ec32b20167247570c74e537cdb1b4fee28c7a;p=cipher-tools.git Column transposition written but untested --- diff --git a/cipher.py b/cipher.py index bc173a7..d857e04 100644 --- a/cipher.py +++ b/cipher.py @@ -3,7 +3,7 @@ import collections import norms import logging import math -from itertools import zip_longest +from itertools import zip_longest, repeat from segment import segment from multiprocessing import Pool @@ -67,20 +67,22 @@ def ngrams(text, n): """ return [text[i:i+n] for i in range(len(text)-n+1)] -def every_nth(text, n): +def every_nth(text, n, fillvalue=''): """Returns n strings, each of which consists of every nth character, starting with the 0th, 1st, 2nd, ... (n-1)th character >>> every_nth(string.ascii_lowercase, 5) ['afkpuz', 'bglqv', 'chmrw', 'dinsx', 'ejoty'] - >>> every_nth(string.ascii_lowercase, 1) + >>> every_nth(string.ascii_lowercase, 1) ['abcdefghijklmnopqrstuvwxyz'] >>> every_nth(string.ascii_lowercase, 26) # doctest: +NORMALIZE_WHITESPACE ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'] + >>> every_nth(string.ascii_lowercase, 5, fillvalue='!') + ['afkpuz', 'bglqv!', 'chmrw!', 'dinsx!', 'ejoty!'] """ split_text = [text[i:i+n] for i in range(0, len(text), n)] - return [''.join(l) for l in zip_longest(*split_text, fillvalue='')] + return [''.join(l) for l in zip_longest(*split_text, fillvalue=fillvalue)] def combine_every_nth(split_text): """Reforms a text split into every_nth strings @@ -95,6 +97,36 @@ def combine_every_nth(split_text): return ''.join([''.join(l) for l in zip_longest(*split_text, fillvalue='')]) +def transpose(items, transposition): + """Moves items around according to the given transposition + + >>> transpose(['a', 'b', 'c', 'd'], [0,1,2,3]) + ['a', 'b', 'c', 'd'] + >>> transpose(['a', 'b', 'c', 'd'], [3,1,2,0]) + ['d', 'b', 'c', 'a'] + >>> transpose([10,11,12,13,14,15], [3,2,4,1,5,0]) + [13, 12, 14, 11, 15, 10] + """ + transposed = list(repeat('', len(transposition))) + for p, t in enumerate(transposition): + transposed[p] = items[t] + return transposed + +def untranspose(items, transposition): + """Undoes a transpose + + >>> untranspose(['a', 'b', 'c', 'd'], [0,1,2,3]) + ['a', 'b', 'c', 'd'] + >>> untranspose(['d', 'b', 'c', 'a'], [3,1,2,0]) + ['a', 'b', 'c', 'd'] + >>> untranspose([13, 12, 14, 11, 15, 10], [3,2,4,1,5,0]) + [10, 11, 12, 13, 14, 15] + """ + transposed = list(repeat('', len(transposition))) + for p, t in enumerate(transposition): + transposed[t] = items[p] + return transposed + def frequencies(text): """Count the number of occurrences of each character in text @@ -387,6 +419,20 @@ def scytale_decipher(message, rows): return ''.join([''.join(c) for c in zip_longest(*columns, fillvalue='')]) +def transpositions_of(keyword): + transpositions = [] + key = deduplicate(keyword) + for l in sorted(key): + transpositions += [key.index(l)] + return transpositions + +def column_transposition_encipher(message, keyword): + transpositions = transpositions_of(keyword) + rows = every_nth(message, len(transpositions), fillvalue=' ') + transposed_rows = [transpose(row, transpositions) for row in rows] + return combine_every_nth(transposed_rows) + + def caesar_break(message, metric=norms.euclidean_distance, target_counts=normalised_english_counts,