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XOR Cipher: doctests and bug fixes #10840

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merged 4 commits into from
Oct 29, 2023
Merged

XOR Cipher: doctests and bug fixes #10840

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1fc3d75
Fixed bug with key modulus wrapping. Should be wrapping on 256, not 255.
FarzadHayat Oct 23, 2023
957fc03
Fixed bug with incorrect assertion type in decrypt function.
FarzadHayat Oct 23, 2023
9cfeeef
Added doctests for 4 out of 6 methods
FarzadHayat Oct 23, 2023
32f7cc4
Merge branch 'TheAlgorithms:master' into xor-cipher
FarzadHayat Oct 23, 2023
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91 changes: 82 additions & 9 deletions ciphers/xor_cipher.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,22 @@ def encrypt(self, content: str, key: int) -> list[str]:
output: encrypted string 'content' as a list of chars
if key not passed the method uses the key by the constructor.
otherwise key = 1

Empty list
>>> XORCipher().encrypt("", 5)
[]

One key
>>> XORCipher().encrypt("hallo welt", 1)
['i', '`', 'm', 'm', 'n', '!', 'v', 'd', 'm', 'u']

Normal key
>>> XORCipher().encrypt("HALLO WELT", 32)
['h', 'a', 'l', 'l', 'o', '\\x00', 'w', 'e', 'l', 't']

Key greater than 255
>>> XORCipher().encrypt("hallo welt", 256)
['h', 'a', 'l', 'l', 'o', ' ', 'w', 'e', 'l', 't']
"""

# precondition
Expand All @@ -44,7 +60,7 @@ def encrypt(self, content: str, key: int) -> list[str]:
key = key or self.__key or 1

# make sure key is an appropriate size
key %= 255
key %= 256

return [chr(ord(ch) ^ key) for ch in content]

Expand All @@ -54,16 +70,32 @@ def decrypt(self, content: str, key: int) -> list[str]:
output: decrypted string 'content' as a list of chars
if key not passed the method uses the key by the constructor.
otherwise key = 1

Empty list
>>> XORCipher().decrypt("", 5)
[]

One key
>>> XORCipher().decrypt("hallo welt", 1)
['i', '`', 'm', 'm', 'n', '!', 'v', 'd', 'm', 'u']

Normal key
>>> XORCipher().decrypt("HALLO WELT", 32)
['h', 'a', 'l', 'l', 'o', '\\x00', 'w', 'e', 'l', 't']

Key greater than 255
>>> XORCipher().decrypt("hallo welt", 256)
['h', 'a', 'l', 'l', 'o', ' ', 'w', 'e', 'l', 't']
"""

# precondition
assert isinstance(key, int)
assert isinstance(content, list)
assert isinstance(content, str)

key = key or self.__key or 1

# make sure key is an appropriate size
key %= 255
key %= 256

return [chr(ord(ch) ^ key) for ch in content]

Expand All @@ -73,6 +105,22 @@ def encrypt_string(self, content: str, key: int = 0) -> str:
output: encrypted string 'content'
if key not passed the method uses the key by the constructor.
otherwise key = 1

Empty list
>>> XORCipher().encrypt_string("", 5)
''

One key
>>> XORCipher().encrypt_string("hallo welt", 1)
'i`mmn!vdmu'

Normal key
>>> XORCipher().encrypt_string("HALLO WELT", 32)
'hallo\\x00welt'

Key greater than 255
>>> XORCipher().encrypt_string("hallo welt", 256)
'hallo welt'
"""

# precondition
Expand All @@ -81,9 +129,8 @@ def encrypt_string(self, content: str, key: int = 0) -> str:

key = key or self.__key or 1

# make sure key can be any size
while key > 255:
key -= 255
# make sure key is an appropriate size
key %= 256

# This will be returned
ans = ""
Expand All @@ -99,6 +146,22 @@ def decrypt_string(self, content: str, key: int = 0) -> str:
output: decrypted string 'content'
if key not passed the method uses the key by the constructor.
otherwise key = 1

Empty list
>>> XORCipher().decrypt_string("", 5)
''

One key
>>> XORCipher().decrypt_string("hallo welt", 1)
'i`mmn!vdmu'

Normal key
>>> XORCipher().decrypt_string("HALLO WELT", 32)
'hallo\\x00welt'

Key greater than 255
>>> XORCipher().decrypt_string("hallo welt", 256)
'hallo welt'
"""

# precondition
Expand All @@ -107,9 +170,8 @@ def decrypt_string(self, content: str, key: int = 0) -> str:

key = key or self.__key or 1

# make sure key can be any size
while key > 255:
key -= 255
# make sure key is an appropriate size
key %= 256

# This will be returned
ans = ""
Expand All @@ -132,6 +194,9 @@ def encrypt_file(self, file: str, key: int = 0) -> bool:
assert isinstance(file, str)
assert isinstance(key, int)

# make sure key is an appropriate size
key %= 256

try:
with open(file) as fin, open("encrypt.out", "w+") as fout:
# actual encrypt-process
Expand All @@ -156,6 +221,9 @@ def decrypt_file(self, file: str, key: int) -> bool:
assert isinstance(file, str)
assert isinstance(key, int)

# make sure key is an appropriate size
key %= 256

try:
with open(file) as fin, open("decrypt.out", "w+") as fout:
# actual encrypt-process
Expand All @@ -168,6 +236,11 @@ def decrypt_file(self, file: str, key: int) -> bool:
return True


if __name__ == "__main__":
from doctest import testmod

testmod()

# Tests
# crypt = XORCipher()
# key = 67
Expand Down