57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
"""
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Copyright (C) 2012 Bo Zhu http://about.bozhu.me
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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DEALINGS IN THE SOFTWARE.
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"""
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def KSA(key):
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keylength = len(key)
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S = range(256)
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j = 0
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for i in range(256):
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j = (j + S[i] + key[i % keylength]) % 256
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S[i], S[j] = S[j], S[i] # swap
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return S
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def PRGA(S):
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i = 0
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j = 0
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while True:
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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] # swap
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K = S[(S[i] + S[j]) % 256]
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yield K
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def RC4(key):
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S = KSA(key)
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return PRGA(S)
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def RC4Key(key):
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return RC4([ord(c) for c in key])
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def crypt(keystream, plaintext):
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return "".join([chr(ord(c) ^ keystream.next()) for c in plaintext]) |