def get_widget(self):
""" Get the widget for this cipher.
Returns:
A Gtk.Widget used to control this plugin.
"""
if self._plugin_controller is None:
self._plugin_controller = PluginController(self._parent, self)
return self._plugin_controller.get_widget()
class VigenereCipher(Cipher):
"""
An implementation of Vigeneres cipher.
"""
_ASIZE = ord('Z') - ord('A') + 1
_START = ord('A')
def __init__(self, parent):
""" Create a new VigenereCipher instance.
Args:
parent: a class that provides an interface to CryptographyStudio
"""
self._parent = parent
self._plugin_controller = None
def encrypt(self, plaintext, key):
""" Encrypt the given text.
Args:
plaintext: string, text to encrypt
key: strin, key used for encryption
Returns:
String containing encrypted text.
>>> VigenereCipher().encrypt('THOMASJEFFERSON', 'PET')
'ILHBELYIYUIKHSG'
"""
return ''.join(self._trans(plaintext, key, self._encchar))
def decrypt(self, ciphertext, key):
""" Decrypt the given text.
Args:
ciphertext: string, text to decrypt
key: string, key used for decryption
Returns:
String containing decrypted text.
>>> VigenereCipher().decrypt('ILHBELYIYUIKHSG', 'PET')
'THOMASJEFFERSON'
"""
return ''.join(self._trans(ciphertext, key, self._decchar))
def get_widget(self):
""" Get the widget for this cipher.
Returns:
A Gtk.Widget used to control this plugin.
"""
if self._plugin_controller is None:
self._plugin_controller = PluginController(self._parent, self)
return self._plugin_controller.get_widget()
@classmethod
def _trans(cls, text, key, encfunc):
""" Transform each letter of the given text.
i-th letter is transformed by using (i mod len(key))-th letter of the
key.
Args:
text: string, text to transform
key: string, key used for transformation
encfunct: function used for transformation -- it must receive a
text letter and a key letter as input and return a transformed
letter
"""
key = key.upper()
k = len(key)
kp = 0
for i, c in enumerate(text.upper()):
if ord('A') <= ord(c) <= ord('Z'):
yield encfunc(c, key[kp])
kp = (kp + 1) % k
else:
yield c
@classmethod
def _modad(cls, c, k):
""" Add ASCII values of two letters in a maner defined by Vigenere's
cipher.
Args:
c: an integer ASCII value of uppercase english letter
k: another integer ASCII value of uppercase english letter
Returns:
ASCII value of the resulting character.
"""
c += (1 - 2*(c>0)) * cls._START
k += (1 - 2*(k>0)) * cls._START
return cls._START + (c + k) % cls._ASIZE
@classmethod
def _encchar(cls, c, k):
""" Encrypt a character with the given key character.
Args:
c: an uppercase english letter
k: an uppsercase english letter used as a key
Return:
Resulting encrypted letter.
"""
return chr(cls._modad(ord(c), ord(k)))
@classmethod
def _decchar(cls, c, k):
""" Decrypt a character with the given key character.
Args:
c: an uppercase english letter
k: an uppsercase english letter used as a key
Return:
Resulting decrypted letter.
"""
return chr(cls._modad(ord(c), -ord(k)))
