52 lines
1.9 KiB
Python
52 lines
1.9 KiB
Python
# This library is free software: you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation, either
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# version 3 of the License, or (at your option) any later version.
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library. If not, see <http://www.gnu.org/licenses/> or <http://www.gnu.org/licenses/lgpl.txt>.
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class ARC4(object):
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state = None
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i = 0
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j = 0
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def __init__(self, key):
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# Split up the key into a list
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if isinstance(key, str):
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key = [ord(c) for c in key]
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else:
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key = [c for c in key]
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#Key-scheduling algorithm (KSA)
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self.state = [n for n in range(256)]
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j = 0
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for i in range(256):
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j = (j + self.state[i] + key[i % len(key)]) % 256
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self.state[i], self.state[j] = self.state[j], self.state[i]
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def update(self, value):
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chars = []
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random_gen = self._random_generator()
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for char in value:
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if isinstance(value, str):
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byte = ord(char)
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else:
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byte = char
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updated_byte = byte ^ next(random_gen)
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chars.append(updated_byte)
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return bytes(bytearray(chars))
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def _random_generator(self):
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#Pseudo-Random Generation Algorithm (PRGA)
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while True:
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self.i = (self.i + 1) % 256
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self.j = (self.j + self.state[self.i]) % 256
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self.state[self.i], self.state[self.j] = self.state[self.j], self.state[self.i]
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yield self.state[(self.state[self.i] + self.state[self.j]) % 256]
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