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