mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-27 15:01:08 +00:00
76 lines
2.0 KiB
Python
76 lines
2.0 KiB
Python
|
"""
|
||
|
|
https://en.wikipedia.org/wiki/Running_key_cipher
|
||
|
|
"""
|
||
|
|
|
||
|
|
|
||
|
|
def running_key_encrypt(key: str, plaintext: str) -> str:
|
||
|
|
"""
|
||
|
|
Encrypts the plaintext using the Running Key Cipher.
|
||
|
|
|
||
|
|
:param key: The running key (long piece of text).
|
||
|
|
:param plaintext: The plaintext to be encrypted.
|
||
|
|
:return: The ciphertext.
|
||
|
|
"""
|
||
|
|
plaintext = plaintext.replace(" ", "").upper()
|
||
|
|
key = key.replace(" ", "").upper()
|
||
|
|
key_length = len(key)
|
||
|
|
ciphertext = []
|
||
|
|
ord_a = ord("A")
|
||
|
|
|
||
|
|
for i, char in enumerate(plaintext):
|
||
|
|
p = ord(char) - ord_a
|
||
|
|
k = ord(key[i % key_length]) - ord_a
|
||
|
|
c = (p + k) % 26
|
||
|
|
ciphertext.append(chr(c + ord_a))
|
||
|
|
|
||
|
|
return "".join(ciphertext)
|
||
|
|
|
||
|
|
|
||
|
|
def running_key_decrypt(key: str, ciphertext: str) -> str:
|
||
|
|
"""
|
||
|
|
Decrypts the ciphertext using the Running Key Cipher.
|
||
|
|
|
||
|
|
:param key: The running key (long piece of text).
|
||
|
|
:param ciphertext: The ciphertext to be decrypted.
|
||
|
|
:return: The plaintext.
|
||
|
|
"""
|
||
|
|
ciphertext = ciphertext.replace(" ", "").upper()
|
||
|
|
key = key.replace(" ", "").upper()
|
||
|
|
key_length = len(key)
|
||
|
|
plaintext = []
|
||
|
|
ord_a = ord("A")
|
||
|
|
|
||
|
|
for i, char in enumerate(ciphertext):
|
||
|
|
c = ord(char) - ord_a
|
||
|
|
k = ord(key[i % key_length]) - ord_a
|
||
|
|
p = (c - k) % 26
|
||
|
|
plaintext.append(chr(p + ord_a))
|
||
|
|
|
||
|
|
return "".join(plaintext)
|
||
|
|
|
||
|
|
|
||
|
|
def test_running_key_encrypt() -> None:
|
||
|
|
"""
|
||
|
|
>>> key = "How does the duck know that? said Victor"
|
||
|
|
>>> ciphertext = running_key_encrypt(key, "DEFEND THIS")
|
||
|
|
>>> running_key_decrypt(key, ciphertext) == "DEFENDTHIS"
|
||
|
|
True
|
||
|
|
"""
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
import doctest
|
||
|
|
|
||
|
|
doctest.testmod()
|
||
|
|
test_running_key_encrypt()
|
||
|
|
|
||
|
|
plaintext = input("Enter the plaintext: ").upper()
|
||
|
|
print(f"\n{plaintext = }")
|
||
|
|
|
||
|
|
key = "How does the duck know that? said Victor"
|
||
|
|
encrypted_text = running_key_encrypt(key, plaintext)
|
||
|
|
print(f"{encrypted_text = }")
|
||
|
|
|
||
|
|
decrypted_text = running_key_decrypt(key, encrypted_text)
|
||
|
|
print(f"{decrypted_text = }")
|