def vigenere(text, key, encOrDec):
"""
Description:
A cipher that uses a tabula recta to encode text.
Encoding equation:
(letter + key_letter) % 26
Decoding equation:
(letter - key_letter) % 26
"""
text = ltn(text)
key = ltnKey(key)
result = []
counter = 0
enOrDec = -1 if encOrDec else 1 #True for decode, False for encode
for x in text:
if counter == len(key):
counter = 0
if type(x) == int:
result.append((x + (key[counter] * enOrDec)) % 26)
counter += 1
else:
result.append(x)
return ntl(result)
def beaufort(text, key):
"""
Description:
A cipher that uses a tabula recta to encode/decode text.
It's quite similar to Vignere, but its table starts from "Z" rather than "A".
Equation:
(key letter - letter) % 26
Doctests:
>>> beaufort("this is a test with a weak key.", "key")
'rxqs wg k lusl cclr k iuku ogg.'
>>> beaufort("rxqs wg k lusl cclr k iuku ogg.", "key")
'this is a test with a weak key.'
>>> beaufort("abc", "defghijklmnop")
'ddd'
"""
text = ltn(text)
key = ltnKey(key)
result = []
counter = 0
for x in text:
if counter == len(key):
counter = 0
if type(x) == int:
result.append((key[counter] - x) % 26)
counter += 1
else:
result.append(x)
return ntl(result)
def affine(text, multiplier, shift, encOrDec):
"""
Description:
A cipher similar to Caesar Shift, but uses a multiplier to further alter the text.
Note that the multiplier MUST be coprime to the alphabet size, as
using an improper multiplier will result in problems when decoding.
Program Notes:
For the boolean variable encOrDec, False will encode text and True will decode text.
The multiplier inverse is derived by finding a number between 1 and 25 that satisfies this equation:
number * multiplier % 26 == 1
Encoding equation:
(multiplier * [individual letter] + shift) % [alphabet size]
Decoding equation:
(multiplier inverse * ([individual letter] - shift) % [alphabet size]
Doctests:
>>> affine("this is a test!", 3, 15, False)
'uknr nr p ubru!'
>>> affine("uknr nr p ubru!", 3, 15, True)
'this is a test!
>>> affine("", 1, 3, False)
''
>>> affine("lorem ipsum dolor sit amet", 41, 9, False)
'slerh zatxh clsle tzi jhri'
>>> affine("slerh zatxh clsle tzi jhri", 41, 9, True)
"""
assert any([1 if multiplier % x == 0 else 0 for x in [2, 13, 26]
]) != True, "Multiplier must be coprime to 26!"
assert 0 < shift < 26, "Shift must be between 1 and 25!"
result = []
if encOrDec:
for n in range(1, 26):
if n * multiplier % 26 == 1:
multiplierInverse = n
break
formula = (lambda x: (multiplierInverse * (x - shift)) % 26)
else:
formula = (lambda x: (multiplier * x + shift) % 26)
for x in ltn(text):
if type(x) == int:
result.append(formula(x))
else:
result.append(x)
return ntl(result)
def atbash(text):
"""
Description:
A cipher that replaces each letter in text with its "opposite" letter.
Equation:
(abs(letter_position - 25))
Doctests:
>>> atbash("abcdefghijklmnopqrstuvwxyz")
'zyxwvutsrqponmlkjihgfedcba'
"""
nums = []
for x in ltn(text):
if type(x) == int:
nums.append(abs(x - 25))
else:
nums.append(x)
return ntl(nums)
def caesar(text, shift):
"""
Description:
A cipher that shifts each letter by n positions.
Equation:
(letter + shift) % 26
Test Cases:
>>> caesar("abcdefghijklmnopqrstuvwxyz", 1)
'bcdefghijklmnopqrstuvwxyza'
>>> caesar("abcdefghijklmnopqrstuvwxyz", 25)
'zabcdefghijklmnopqrstuvwxy'
>>> caesar("abcdefghijklmnopqrstuvwxyz", 13)
'nopqrstuvwxyzabcdefghijklm'
"""
assert 0 < shift < 26, "Shift must be between 1 and 25!"
nums = []
for x in ltn(text):
if type(x) == int:
nums.append((x + shift) % 26)
else:
nums.append(x)
return ntl(nums)