39 lines
939 B
Python
39 lines
939 B
Python
""" Python implementation of Arcfour encryption algorithm.
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See https://en.wikipedia.org/wiki/RC4
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This code is in the public domain.
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"""
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from typing import Sequence
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class Arcfour:
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def __init__(self, key: Sequence[int]) -> None:
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# because Py3 range is not indexable
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s = [i for i in range(256)]
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j = 0
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klen = len(key)
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for i in range(256):
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j = (j + s[i] + key[i % klen]) % 256
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(s[i], s[j]) = (s[j], s[i])
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self.s = s
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(self.i, self.j) = (0, 0)
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return
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def process(self, data: bytes) -> bytes:
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(i, j) = (self.i, self.j)
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s = self.s
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r = b''
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for c in iter(data):
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i = (i+1) % 256
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j = (j+s[i]) % 256
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(s[i], s[j]) = (s[j], s[i])
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k = s[(s[i]+s[j]) % 256]
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r += bytes((c ^ k,))
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(self.i, self.j) = (i, j)
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return r
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encrypt = decrypt = process
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