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269 lines
6.8 KiB
Python
269 lines
6.8 KiB
Python
"""
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author: Christian Bender
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date: 21.12.2017
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class: XORCipher
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This class implements the XOR-cipher algorithm and provides
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some useful methods for encrypting and decrypting strings and
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files.
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Overview about methods
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- encrypt : list of char
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- decrypt : list of char
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- encrypt_string : str
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- decrypt_string : str
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- encrypt_file : boolean
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- decrypt_file : boolean
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"""
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from __future__ import annotations
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class XORCipher:
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def __init__(self, key: int = 0):
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"""
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simple constructor that receives a key or uses
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default key = 0
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"""
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# private field
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self.__key = key
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def encrypt(self, content: str, key: int) -> list[str]:
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"""
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input: 'content' of type string and 'key' of type int
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output: encrypted string 'content' as a list of chars
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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Empty list
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>>> XORCipher().encrypt("", 5)
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[]
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One key
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>>> XORCipher().encrypt("hallo welt", 1)
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['i', '`', 'm', 'm', 'n', '!', 'v', 'd', 'm', 'u']
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Normal key
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>>> XORCipher().encrypt("HALLO WELT", 32)
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['h', 'a', 'l', 'l', 'o', '\\x00', 'w', 'e', 'l', 't']
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Key greater than 255
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>>> XORCipher().encrypt("hallo welt", 256)
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['h', 'a', 'l', 'l', 'o', ' ', 'w', 'e', 'l', 't']
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"""
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# precondition
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assert isinstance(key, int)
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assert isinstance(content, str)
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key = key or self.__key or 1
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# make sure key is an appropriate size
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key %= 256
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return [chr(ord(ch) ^ key) for ch in content]
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def decrypt(self, content: str, key: int) -> list[str]:
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"""
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input: 'content' of type list and 'key' of type int
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output: decrypted string 'content' as a list of chars
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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Empty list
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>>> XORCipher().decrypt("", 5)
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[]
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One key
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>>> XORCipher().decrypt("hallo welt", 1)
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['i', '`', 'm', 'm', 'n', '!', 'v', 'd', 'm', 'u']
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Normal key
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>>> XORCipher().decrypt("HALLO WELT", 32)
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['h', 'a', 'l', 'l', 'o', '\\x00', 'w', 'e', 'l', 't']
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Key greater than 255
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>>> XORCipher().decrypt("hallo welt", 256)
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['h', 'a', 'l', 'l', 'o', ' ', 'w', 'e', 'l', 't']
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"""
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# precondition
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assert isinstance(key, int)
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assert isinstance(content, str)
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key = key or self.__key or 1
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# make sure key is an appropriate size
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key %= 256
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return [chr(ord(ch) ^ key) for ch in content]
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def encrypt_string(self, content: str, key: int = 0) -> str:
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"""
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input: 'content' of type string and 'key' of type int
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output: encrypted string 'content'
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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Empty list
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>>> XORCipher().encrypt_string("", 5)
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''
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One key
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>>> XORCipher().encrypt_string("hallo welt", 1)
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'i`mmn!vdmu'
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Normal key
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>>> XORCipher().encrypt_string("HALLO WELT", 32)
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'hallo\\x00welt'
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Key greater than 255
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>>> XORCipher().encrypt_string("hallo welt", 256)
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'hallo welt'
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"""
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# precondition
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assert isinstance(key, int)
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assert isinstance(content, str)
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key = key or self.__key or 1
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# make sure key is an appropriate size
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key %= 256
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# This will be returned
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ans = ""
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for ch in content:
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ans += chr(ord(ch) ^ key)
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return ans
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def decrypt_string(self, content: str, key: int = 0) -> str:
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"""
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input: 'content' of type string and 'key' of type int
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output: decrypted string 'content'
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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Empty list
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>>> XORCipher().decrypt_string("", 5)
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''
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One key
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>>> XORCipher().decrypt_string("hallo welt", 1)
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'i`mmn!vdmu'
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Normal key
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>>> XORCipher().decrypt_string("HALLO WELT", 32)
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'hallo\\x00welt'
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Key greater than 255
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>>> XORCipher().decrypt_string("hallo welt", 256)
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'hallo welt'
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"""
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# precondition
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assert isinstance(key, int)
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assert isinstance(content, str)
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key = key or self.__key or 1
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# make sure key is an appropriate size
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key %= 256
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# This will be returned
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ans = ""
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for ch in content:
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ans += chr(ord(ch) ^ key)
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return ans
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def encrypt_file(self, file: str, key: int = 0) -> bool:
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"""
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input: filename (str) and a key (int)
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output: returns true if encrypt process was
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successful otherwise false
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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"""
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# precondition
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assert isinstance(file, str)
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assert isinstance(key, int)
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# make sure key is an appropriate size
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key %= 256
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try:
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with open(file) as fin, open("encrypt.out", "w+") as fout:
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# actual encrypt-process
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for line in fin:
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fout.write(self.encrypt_string(line, key))
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except OSError:
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return False
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return True
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def decrypt_file(self, file: str, key: int) -> bool:
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"""
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input: filename (str) and a key (int)
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output: returns true if decrypt process was
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successful otherwise false
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if key not passed the method uses the key by the constructor.
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otherwise key = 1
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"""
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# precondition
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assert isinstance(file, str)
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assert isinstance(key, int)
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# make sure key is an appropriate size
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key %= 256
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try:
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with open(file) as fin, open("decrypt.out", "w+") as fout:
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# actual encrypt-process
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for line in fin:
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fout.write(self.decrypt_string(line, key))
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except OSError:
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return False
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return True
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if __name__ == "__main__":
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from doctest import testmod
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testmod()
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# Tests
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# crypt = XORCipher()
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# key = 67
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# # test encrypt
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# print(crypt.encrypt("hallo welt",key))
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# # test decrypt
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# print(crypt.decrypt(crypt.encrypt("hallo welt",key), key))
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# # test encrypt_string
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# print(crypt.encrypt_string("hallo welt",key))
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# # test decrypt_string
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# print(crypt.decrypt_string(crypt.encrypt_string("hallo welt",key),key))
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# if (crypt.encrypt_file("test.txt",key)):
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# print("encrypt successful")
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# else:
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# print("encrypt unsuccessful")
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# if (crypt.decrypt_file("encrypt.out",key)):
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# print("decrypt successful")
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# else:
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# print("decrypt unsuccessful")
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