From: Neil Smith <neil.git@njae.me.uk>
Date: Mon, 14 Jul 2014 19:56:24 +0000 (+0100)
Subject: Breaking caesar ciphers
X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=25fe3d49e738be3e1f03d15445cad78bf1c94bde;p=cipher-training.git

Breaking caesar ciphers
---

diff --git a/cipher.py b/cipher.py
index 5398714..e71902d 100644
--- a/cipher.py
+++ b/cipher.py
@@ -9,73 +9,6 @@ from itertools import zip_longest, cycle, chain
 from language_models import unaccent, sanitise
 
 
-modular_division_table = [[0]*26 for _ in range(26)]
-for a in range(26):
-    for b in range(26):
-        c = (a * b) % 26
-        modular_division_table[b][c] = a
-
-
-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)
-    ['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 = chunks(text, n, 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
-
-    >>> combine_every_nth(every_nth(string.ascii_lowercase, 5))
-    'abcdefghijklmnopqrstuvwxyz'
-    >>> combine_every_nth(every_nth(string.ascii_lowercase, 1))
-    'abcdefghijklmnopqrstuvwxyz'
-    >>> combine_every_nth(every_nth(string.ascii_lowercase, 26))
-    'abcdefghijklmnopqrstuvwxyz'
-    """
-    return ''.join([''.join(l)
-                    for l in zip_longest(*split_text, fillvalue='')])
-
-def chunks(text, n, fillvalue=None):
-    """Split a text into chunks of n characters
-
-    >>> chunks('abcdefghi', 3)
-    ['abc', 'def', 'ghi']
-    >>> chunks('abcdefghi', 4)
-    ['abcd', 'efgh', 'i']
-    >>> chunks('abcdefghi', 4, fillvalue='!')
-    ['abcd', 'efgh', 'i!!!']
-    """
-    if fillvalue:
-        padding = fillvalue[0] * (n - len(text) % n)
-    else:
-        padding = ''
-    return [(text+padding)[i:i+n] for i in range(0, len(text), n)]
-
-def deduplicate(text):
-    """If a string contains duplicate letters, remove all but the first. Retain
-    the order of the letters.
-
-    >>> deduplicate('cat')
-    ['c', 'a', 't']
-    >>> deduplicate('happy')
-    ['h', 'a', 'p', 'y']
-    >>> deduplicate('cattca')
-    ['c', 'a', 't']
-    """
-    return list(collections.OrderedDict.fromkeys(text))
-
-
 def caesar_encipher_letter(accented_letter, shift):
     """Encipher a letter, given a shift amount
 
@@ -152,78 +85,6 @@ def caesar_decipher(message, shift):
     """
     return caesar_encipher(message, -shift)
 
-def affine_encipher_letter(accented_letter, multiplier=1, adder=0,
-                           one_based=True):
-    """Encipher a letter, given a multiplier and adder
-    >>> ''.join([affine_encipher_letter(l, 3, 5, True) \
-            for l in string.ascii_uppercase])
-    'HKNQTWZCFILORUXADGJMPSVYBE'
-    >>> ''.join([affine_encipher_letter(l, 3, 5, False) \
-            for l in string.ascii_uppercase])
-    'FILORUXADGJMPSVYBEHKNQTWZC'
-    """
-    letter = unaccent(accented_letter)
-    if letter in string.ascii_letters:
-        if letter in string.ascii_uppercase:
-            alphabet_start = ord('A')
-        else:
-            alphabet_start = ord('a')
-        letter_number = ord(letter) - alphabet_start
-        if one_based: letter_number += 1
-        cipher_number = (letter_number * multiplier + adder) % 26
-        if one_based: cipher_number -= 1
-        return chr(cipher_number % 26 + alphabet_start)
-    else:
-        return letter
-
-def affine_decipher_letter(letter, multiplier=1, adder=0, one_based=True):
-    """Encipher a letter, given a multiplier and adder
-
-    >>> ''.join([affine_decipher_letter(l, 3, 5, True) \
-            for l in 'HKNQTWZCFILORUXADGJMPSVYBE'])
-    'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
-    >>> ''.join([affine_decipher_letter(l, 3, 5, False) \
-            for l in 'FILORUXADGJMPSVYBEHKNQTWZC'])
-    'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
-    """
-    if letter in string.ascii_letters:
-        if letter in string.ascii_uppercase:
-            alphabet_start = ord('A')
-        else:
-            alphabet_start = ord('a')
-        cipher_number = ord(letter) - alphabet_start
-        if one_based: cipher_number += 1
-        plaintext_number = (
-            modular_division_table[multiplier]
-                                  [(cipher_number - adder) % 26]
-                            )
-        if one_based: plaintext_number -= 1
-        return chr(plaintext_number % 26 + alphabet_start)
-    else:
-        return letter
-
-def affine_encipher(message, multiplier=1, adder=0, one_based=True):
-    """Encipher a message
-
-    >>> affine_encipher('hours passed during which jerico tried every ' \
-           'trick he could think of', 15, 22, True)
-    'lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg jfaoe ls omytd jlaxe mh'
-    """
-    enciphered = [affine_encipher_letter(l, multiplier, adder, one_based)
-                  for l in message]
-    return ''.join(enciphered)
-
-def affine_decipher(message, multiplier=1, adder=0, one_based=True):
-    """Decipher a message
-
-    >>> affine_decipher('lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg ' \
-           'jfaoe ls omytd jlaxe mh', 15, 22, True)
-    'hours passed during which jerico tried every trick he could think of'
-    """
-    enciphered = [affine_decipher_letter(l, multiplier, adder, one_based)
-                  for l in message]
-    return ''.join(enciphered)
-
 
 if __name__ == "__main__":
     import doctest