From 0d469a1c5ce3895f1b3d3ecbf7c58c69d7e0d2ed Mon Sep 17 00:00:00 2001 From: Neil Smith Date: Fri, 25 Oct 2013 19:59:19 +0100 Subject: [PATCH] Scytale enciphering working, but have to think about what to do with a 16 character message and a 5-row scytale --- cipher.py | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/cipher.py b/cipher.py index 2ce1c92..6a138a0 100644 --- a/cipher.py +++ b/cipher.py @@ -2,6 +2,7 @@ import string import collections import norms import logging +import math from itertools import zip_longest from segment import segment @@ -304,6 +305,40 @@ def keyword_decipher(message, keyword, wrap_alphabet=0): cipher_translation = ''.maketrans(cipher_alphabet, string.ascii_lowercase) return message.lower().translate(cipher_translation) +def scytale_encipher(message, rows): + """Enciphers using the scytale transposition cipher + + >>> scytale_encipher('thequickbrownfox', 3) + 'tcnhkfeboqrxuoiw' + >>> scytale_encipher('thequickbrownfox', 4) + 'tubnhirfecooqkwx' + >>> scytale_encipher('thequickbrownfox', 5) + 'tubnhirfecooqkwx' + >>> scytale_encipher('thequickbrownfox', 6) + 'tqcrnxhukofeibwo' + >>> scytale_encipher('thequickbrownfox', 7) + 'tqcrnxhukofeibwo' + """ + row_length = math.ceil(len(message) / rows) + slices = [message[i:i+row_length] for i in range(0, len(message), row_length)] + return ''.join([''.join(r) for r in zip_longest(*slices, fillvalue='')]) + +def scytale_decipher(message, rows): + """Deciphers using the scytale transposition cipher + + >>> scytale_decipher('tcnhkfeboqrxuoiw', 3) + 'thequickbrownfox' + """ + cols = math.ceil(len(message) / rows) + if len(message) % rows == 0: + part_cols = 0 + else: + part_cols = rows - len(message) % rows + full_cols = cols - part_cols + columns = [message[i:i+rows] for i in range(0, full_cols * rows, rows)] + \ + [message[i:i+rows-1] for i in range(full_cols * rows, len(message), rows - 1)] + return ''.join([''.join(c) for c in zip_longest(*columns, fillvalue='')]) + def caesar_break(message, metric=norms.euclidean_distance, target_frequencies=normalised_english_counts, message_frequency_scaling=norms.normalise): """Breaks a Caesar cipher using frequency analysis -- 2.34.1