+"""A set of ciphers with implementations for both enciphering and deciphering
+them. See cipherbreak for automatic breaking of these ciphers
+"""
+
import string
-from language_models import *
+import collections
+from enum import Enum
+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 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
alphabet_start = ord('A')
else:
alphabet_start = ord('a')
- return chr(((ord(letter) - alphabet_start + shift) % 26) +
+ return chr(((ord(letter) - alphabet_start + shift) % 26) +
alphabet_start)
else:
return letter
def caesar_decipher_letter(letter, shift):
"""Decipher a letter, given a shift amount
-
+
>>> caesar_decipher_letter('b', 1)
'a'
>>> caesar_decipher_letter('b', 2)
def caesar_encipher(message, shift):
"""Encipher a message with the Caesar cipher of given shift
-
+
>>> caesar_encipher('abc', 1)
'bcd'
>>> caesar_encipher('abc', 2)
def caesar_decipher(message, shift):
"""Decipher a message with the Caesar cipher of given shift
-
+
>>> caesar_decipher('bcd', 1)
'abc'
>>> caesar_decipher('cde', 2)
"""
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)
+
+
+class KeywordWrapAlphabet(Enum):
+ """Ways of wrapping the alphabet for keyword-based substitution ciphers."""
+ from_a = 1
+ from_last = 2
+ from_largest = 3
+
+
+def keyword_cipher_alphabet_of(keyword,
+ wrap_alphabet=KeywordWrapAlphabet.from_a):
+ """Find the cipher alphabet given a keyword.
+ wrap_alphabet controls how the rest of the alphabet is added
+ after the keyword.
+
+ >>> keyword_cipher_alphabet_of('bayes')
+ 'bayescdfghijklmnopqrtuvwxz'
+ >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_a)
+ 'bayescdfghijklmnopqrtuvwxz'
+ >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_last)
+ 'bayestuvwxzcdfghijklmnopqr'
+ >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_largest)
+ 'bayeszcdfghijklmnopqrtuvwx'
+ """
+ if wrap_alphabet == KeywordWrapAlphabet.from_a:
+ cipher_alphabet = ''.join(deduplicate(sanitise(keyword) +
+ string.ascii_lowercase))
+ else:
+ if wrap_alphabet == KeywordWrapAlphabet.from_last:
+ last_keyword_letter = deduplicate(sanitise(keyword))[-1]
+ else:
+ last_keyword_letter = sorted(sanitise(keyword))[-1]
+ last_keyword_position = string.ascii_lowercase.find(
+ last_keyword_letter) + 1
+ cipher_alphabet = ''.join(
+ deduplicate(sanitise(keyword) +
+ string.ascii_lowercase[last_keyword_position:] +
+ string.ascii_lowercase))
+ return cipher_alphabet
+
+
+def keyword_encipher(message, keyword,
+ wrap_alphabet=KeywordWrapAlphabet.from_a):
+ """Enciphers a message with a keyword substitution cipher.
+ wrap_alphabet controls how the rest of the alphabet is added
+ after the keyword.
+ 0 : from 'a'
+ 1 : from the last letter in the sanitised keyword
+ 2 : from the largest letter in the sanitised keyword
+
+ >>> keyword_encipher('test message', 'bayes')
+ 'rsqr ksqqbds'
+ >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_a)
+ 'rsqr ksqqbds'
+ >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_last)
+ 'lskl dskkbus'
+ >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_largest)
+ 'qspq jsppbcs'
+ """
+ cipher_alphabet = keyword_cipher_alphabet_of(keyword, wrap_alphabet)
+ cipher_translation = ''.maketrans(string.ascii_lowercase, cipher_alphabet)
+ return unaccent(message).lower().translate(cipher_translation)
+
+def keyword_decipher(message, keyword,
+ wrap_alphabet=KeywordWrapAlphabet.from_a):
+ """Deciphers a message with a keyword substitution cipher.
+ wrap_alphabet controls how the rest of the alphabet is added
+ after the keyword.
+ 0 : from 'a'
+ 1 : from the last letter in the sanitised keyword
+ 2 : from the largest letter in the sanitised keyword
+
+ >>> keyword_decipher('rsqr ksqqbds', 'bayes')
+ 'test message'
+ >>> keyword_decipher('rsqr ksqqbds', 'bayes', KeywordWrapAlphabet.from_a)
+ 'test message'
+ >>> keyword_decipher('lskl dskkbus', 'bayes', KeywordWrapAlphabet.from_last)
+ 'test message'
+ >>> keyword_decipher('qspq jsppbcs', 'bayes', KeywordWrapAlphabet.from_largest)
+ 'test message'
+ """
+ cipher_alphabet = keyword_cipher_alphabet_of(keyword, wrap_alphabet)
+ cipher_translation = ''.maketrans(cipher_alphabet, string.ascii_lowercase)
+ return message.lower().translate(cipher_translation)
if __name__ == "__main__":
import doctest
projects / cipher-training.git / blobdiff