+++ /dev/null
-from utilities import *
-from language_models import *
-from logger import logger
-
-
-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 affine_encipher_letter(accented_letter, multiplier=1, adder=0, one_based=True):
- """Encipher a letter, given a multiplier and adder
-
- >>> cat(affine_encipher_letter(l, 3, 5, True) \
- for l in string.ascii_letters)
- 'hknqtwzcfiloruxadgjmpsvybeHKNQTWZCFILORUXADGJMPSVYBE'
- >>> cat(affine_encipher_letter(l, 3, 5, False) \
- for l in string.ascii_letters)
- 'filoruxadgjmpsvybehknqtwzcFILORUXADGJMPSVYBEHKNQTWZC'
- """
- # 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
- letter = unaccent(accented_letter)
- if letter in string.ascii_letters:
- letter_number = pos(letter)
- if one_based: letter_number += 1
- cipher_number = (letter_number * multiplier + adder) % 26
- if one_based: cipher_number -= 1
- if letter in string.ascii_uppercase:
- return unpos(cipher_number).upper()
- else:
- return unpos(cipher_number)
- else:
- return letter
-
-def affine_decipher_letter(letter, multiplier=1, adder=0, one_based=True):
- """Encipher a letter, given a multiplier and adder
-
- >>> cat(affine_decipher_letter(l, 3, 5, True) \
- for l in 'hknqtwzcfiloruxadgjmpsvybeHKNQTWZCFILORUXADGJMPSVYBE')
- 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
- >>> cat(affine_decipher_letter(l, 3, 5, False) \
- for l in 'filoruxadgjmpsvybehknqtwzcFILORUXADGJMPSVYBEHKNQTWZC')
- 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
- """
- # 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
- if letter in string.ascii_letters:
- cipher_number = pos(letter)
- if one_based: cipher_number += 1
- plaintext_number = (
- modular_division_table[multiplier]
- [(cipher_number - adder) % 26])
- if one_based: plaintext_number -= 1
- if letter in string.ascii_uppercase:
- return unpos(plaintext_number).upper()
- else:
- return unpos(plaintext_number)
- 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 cat(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 cat(enciphered)
-
-
-
-def affine_break(message, fitness=Pletters):
- """Breaks an affine cipher using frequency analysis
-
- >>> affine_break('lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg jfaoe ls ' \
- 'omytd jlaxe mh jm bfmibj umis hfsul axubafkjamx. ls kffkxwsd jls ' \
- 'ofgbjmwfkiu olfmxmtmwaokttg jlsx ls kffkxwsd jlsi zg tsxwjl. jlsx ' \
- 'ls umfjsd jlsi zg hfsqysxog. ls dmmdtsd mx jls bats mh bkbsf. ls ' \
- 'bfmctsd kfmyxd jls lyj, mztanamyu xmc jm clm cku tmmeaxw kj lai ' \
- 'kxd clm ckuxj.') # doctest: +ELLIPSIS
- ((15, 22, True), -340.601181913...)
- """
- sanitised_message = sanitise(message)
- best_multiplier = 0
- best_adder = 0
- best_one_based = True
- best_fit = float("-inf")
- for one_based in [True, False]:
- for multiplier in [x for x in range(1, 26, 2) if x != 13]:
- for adder in range(26):
- plaintext = affine_decipher(sanitised_message,
- multiplier, adder, one_based)
- fit = fitness(plaintext)
- logger.debug('Affine break attempt using key {0}x+{1} ({2}) '
- 'gives fit of {3} and decrypt starting: {4}'.
- format(multiplier, adder, one_based, fit,
- plaintext[:50]))
- if fit > best_fit:
- best_fit = fit
- best_multiplier = multiplier
- best_adder = adder
- best_one_based = one_based
- logger.info('Affine break best fit with key {0}x+{1} ({2}) gives fit of '
- '{3} and decrypt starting: {4}'.format(
- best_multiplier, best_adder, best_one_based, best_fit,
- affine_decipher(sanitised_message, best_multiplier,
- best_adder, best_one_based)[:50]))
- return (best_multiplier, best_adder, best_one_based), best_fit
projects / cipher-tools.git / blobdiff