1 """A set of ciphers with implementations for both enciphering and deciphering
2 them. See cipherbreak for automatic breaking of these ciphers
8 from itertools
import zip_longest
, cycle
, chain
9 from language_models
import unaccent
, sanitise
12 modular_division_table
= [[0]*26 for _
in range(26)]
16 modular_division_table
[b
][c
] = a
19 def every_nth(text
, n
, fillvalue
=''):
20 """Returns n strings, each of which consists of every nth character,
21 starting with the 0th, 1st, 2nd, ... (n-1)th character
23 >>> every_nth(string.ascii_lowercase, 5)
24 ['afkpuz', 'bglqv', 'chmrw', 'dinsx', 'ejoty']
25 >>> every_nth(string.ascii_lowercase, 1)
26 ['abcdefghijklmnopqrstuvwxyz']
27 >>> every_nth(string.ascii_lowercase, 26) # doctest: +NORMALIZE_WHITESPACE
28 ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
29 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
30 >>> every_nth(string.ascii_lowercase, 5, fillvalue='!')
31 ['afkpuz', 'bglqv!', 'chmrw!', 'dinsx!', 'ejoty!']
33 split_text
= chunks(text
, n
, fillvalue
)
34 return [''.join(l
) for l
in zip_longest(*split_text
, fillvalue
=fillvalue
)]
36 def combine_every_nth(split_text
):
37 """Reforms a text split into every_nth strings
39 >>> combine_every_nth(every_nth(string.ascii_lowercase, 5))
40 'abcdefghijklmnopqrstuvwxyz'
41 >>> combine_every_nth(every_nth(string.ascii_lowercase, 1))
42 'abcdefghijklmnopqrstuvwxyz'
43 >>> combine_every_nth(every_nth(string.ascii_lowercase, 26))
44 'abcdefghijklmnopqrstuvwxyz'
46 return ''.join([''.join(l
)
47 for l
in zip_longest(*split_text
, fillvalue
='')])
49 def chunks(text
, n
, fillvalue
=None):
50 """Split a text into chunks of n characters
52 >>> chunks('abcdefghi', 3)
54 >>> chunks('abcdefghi', 4)
56 >>> chunks('abcdefghi', 4, fillvalue='!')
57 ['abcd', 'efgh', 'i!!!']
60 padding
= fillvalue
[0] * (n
- len(text
) % n
)
63 return [(text
+padding
)[i
:i
+n
] for i
in range(0, len(text
), n
)]
65 def deduplicate(text
):
66 """If a string contains duplicate letters, remove all but the first. Retain
67 the order of the letters.
69 >>> deduplicate('cat')
71 >>> deduplicate('happy')
73 >>> deduplicate('cattca')
76 return list(collections
.OrderedDict
.fromkeys(text
))
79 def caesar_encipher_letter(accented_letter
, shift
):
80 """Encipher a letter, given a shift amount
82 >>> caesar_encipher_letter('a', 1)
84 >>> caesar_encipher_letter('a', 2)
86 >>> caesar_encipher_letter('b', 2)
88 >>> caesar_encipher_letter('x', 2)
90 >>> caesar_encipher_letter('y', 2)
92 >>> caesar_encipher_letter('z', 2)
94 >>> caesar_encipher_letter('z', -1)
96 >>> caesar_encipher_letter('a', -1)
98 >>> caesar_encipher_letter('A', 1)
100 >>> caesar_encipher_letter('é', 1)
103 letter
= unaccent(accented_letter
)
104 if letter
in string
.ascii_letters
:
105 if letter
in string
.ascii_uppercase
:
106 alphabet_start
= ord('A')
108 alphabet_start
= ord('a')
109 return chr(((ord(letter
) - alphabet_start
+ shift
) % 26) +
114 def caesar_decipher_letter(letter
, shift
):
115 """Decipher a letter, given a shift amount
117 >>> caesar_decipher_letter('b', 1)
119 >>> caesar_decipher_letter('b', 2)
122 return caesar_encipher_letter(letter
, -shift
)
124 def caesar_encipher(message
, shift
):
125 """Encipher a message with the Caesar cipher of given shift
127 >>> caesar_encipher('abc', 1)
129 >>> caesar_encipher('abc', 2)
131 >>> caesar_encipher('abcxyz', 2)
133 >>> caesar_encipher('ab cx yz', 2)
135 >>> caesar_encipher('Héllo World!', 2)
138 enciphered
= [caesar_encipher_letter(l
, shift
) for l
in message
]
139 return ''.join(enciphered
)
141 def caesar_decipher(message
, shift
):
142 """Decipher a message with the Caesar cipher of given shift
144 >>> caesar_decipher('bcd', 1)
146 >>> caesar_decipher('cde', 2)
148 >>> caesar_decipher('cd ez ab', 2)
150 >>> caesar_decipher('Jgnnq Yqtnf!', 2)
153 return caesar_encipher(message
, -shift
)
155 def affine_encipher_letter(accented_letter
, multiplier
=1, adder
=0,
157 """Encipher a letter, given a multiplier and adder
158 >>> ''.join([affine_encipher_letter(l, 3, 5, True) \
159 for l in string.ascii_uppercase])
160 'HKNQTWZCFILORUXADGJMPSVYBE'
161 >>> ''.join([affine_encipher_letter(l, 3, 5, False) \
162 for l in string.ascii_uppercase])
163 'FILORUXADGJMPSVYBEHKNQTWZC'
165 letter
= unaccent(accented_letter
)
166 if letter
in string
.ascii_letters
:
167 if letter
in string
.ascii_uppercase
:
168 alphabet_start
= ord('A')
170 alphabet_start
= ord('a')
171 letter_number
= ord(letter
) - alphabet_start
172 if one_based
: letter_number
+= 1
173 cipher_number
= (letter_number
* multiplier
+ adder
) % 26
174 if one_based
: cipher_number
-= 1
175 return chr(cipher_number
% 26 + alphabet_start
)
179 def affine_decipher_letter(letter
, multiplier
=1, adder
=0, one_based
=True):
180 """Encipher a letter, given a multiplier and adder
182 >>> ''.join([affine_decipher_letter(l, 3, 5, True) \
183 for l in 'HKNQTWZCFILORUXADGJMPSVYBE'])
184 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
185 >>> ''.join([affine_decipher_letter(l, 3, 5, False) \
186 for l in 'FILORUXADGJMPSVYBEHKNQTWZC'])
187 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
189 if letter
in string
.ascii_letters
:
190 if letter
in string
.ascii_uppercase
:
191 alphabet_start
= ord('A')
193 alphabet_start
= ord('a')
194 cipher_number
= ord(letter
) - alphabet_start
195 if one_based
: cipher_number
+= 1
197 modular_division_table
[multiplier
]
198 [(cipher_number
- adder
) % 26]
200 if one_based
: plaintext_number
-= 1
201 return chr(plaintext_number
% 26 + alphabet_start
)
205 def affine_encipher(message
, multiplier
=1, adder
=0, one_based
=True):
206 """Encipher a message
208 >>> affine_encipher('hours passed during which jerico tried every ' \
209 'trick he could think of', 15, 22, True)
210 'lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg jfaoe ls omytd jlaxe mh'
212 enciphered
= [affine_encipher_letter(l
, multiplier
, adder
, one_based
)
214 return ''.join(enciphered
)
216 def affine_decipher(message
, multiplier
=1, adder
=0, one_based
=True):
217 """Decipher a message
219 >>> affine_decipher('lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg ' \
220 'jfaoe ls omytd jlaxe mh', 15, 22, True)
221 'hours passed during which jerico tried every trick he could think of'
223 enciphered
= [affine_decipher_letter(l
, multiplier
, adder
, one_based
)
225 return ''.join(enciphered
)
228 class KeywordWrapAlphabet(Enum
):
229 """Ways of wrapping the alphabet for keyword-based substitution ciphers."""
235 def keyword_cipher_alphabet_of(keyword
,
236 wrap_alphabet
=KeywordWrapAlphabet
.from_a
):
237 """Find the cipher alphabet given a keyword.
238 wrap_alphabet controls how the rest of the alphabet is added
241 >>> keyword_cipher_alphabet_of('bayes')
242 'bayescdfghijklmnopqrtuvwxz'
243 >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_a)
244 'bayescdfghijklmnopqrtuvwxz'
245 >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_last)
246 'bayestuvwxzcdfghijklmnopqr'
247 >>> keyword_cipher_alphabet_of('bayes', KeywordWrapAlphabet.from_largest)
248 'bayeszcdfghijklmnopqrtuvwx'
250 if wrap_alphabet
== KeywordWrapAlphabet
.from_a
:
251 cipher_alphabet
= ''.join(deduplicate(sanitise(keyword
) +
252 string
.ascii_lowercase
))
254 if wrap_alphabet
== KeywordWrapAlphabet
.from_last
:
255 last_keyword_letter
= deduplicate(sanitise(keyword
))[-1]
257 last_keyword_letter
= sorted(sanitise(keyword
))[-1]
258 last_keyword_position
= string
.ascii_lowercase
.find(
259 last_keyword_letter
) + 1
260 cipher_alphabet
= ''.join(
261 deduplicate(sanitise(keyword
) +
262 string
.ascii_lowercase
[last_keyword_position
:] +
263 string
.ascii_lowercase
))
264 return cipher_alphabet
267 def keyword_encipher(message
, keyword
,
268 wrap_alphabet
=KeywordWrapAlphabet
.from_a
):
269 """Enciphers a message with a keyword substitution cipher.
270 wrap_alphabet controls how the rest of the alphabet is added
273 1 : from the last letter in the sanitised keyword
274 2 : from the largest letter in the sanitised keyword
276 >>> keyword_encipher('test message', 'bayes')
278 >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_a)
280 >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_last)
282 >>> keyword_encipher('test message', 'bayes', KeywordWrapAlphabet.from_largest)
285 cipher_alphabet
= keyword_cipher_alphabet_of(keyword
, wrap_alphabet
)
286 cipher_translation
= ''.maketrans(string
.ascii_lowercase
, cipher_alphabet
)
287 return unaccent(message
).lower().translate(cipher_translation
)
289 def keyword_decipher(message
, keyword
,
290 wrap_alphabet
=KeywordWrapAlphabet
.from_a
):
291 """Deciphers a message with a keyword substitution cipher.
292 wrap_alphabet controls how the rest of the alphabet is added
295 1 : from the last letter in the sanitised keyword
296 2 : from the largest letter in the sanitised keyword
298 >>> keyword_decipher('rsqr ksqqbds', 'bayes')
300 >>> keyword_decipher('rsqr ksqqbds', 'bayes', KeywordWrapAlphabet.from_a)
302 >>> keyword_decipher('lskl dskkbus', 'bayes', KeywordWrapAlphabet.from_last)
304 >>> keyword_decipher('qspq jsppbcs', 'bayes', KeywordWrapAlphabet.from_largest)
307 cipher_alphabet
= keyword_cipher_alphabet_of(keyword
, wrap_alphabet
)
308 cipher_translation
= ''.maketrans(cipher_alphabet
, string
.ascii_lowercase
)
309 return message
.lower().translate(cipher_translation
)
312 if __name__
== "__main__":