python - 如何使用 Python 解密使用 rc4 加密的文件？

Question

我得到了一个用 rc4 密钥加密的文件。

我得到了那个密钥，想用 python 脚本解密它。

我怎样才能做到这一点？

Answer 1

经过 3 秒的 Google 搜索后发现以下内容：http ://www.emoticcode.net/python/python-implementation-of-rc4-algorithm.html

如此修改：

import base64

data = base64.b64decode("<encrypted file contents>")
key = "<rc4 key>"

S = range(256)
j = 0
out = []

#KSA Phase
for i in range(256):
    j = (j + S[i] + ord( key[i % len(key)] )) % 256
    S[i] , S[j] = S[j] , S[i]

#PRGA Phase
i = j = 0
for char in data:
    i = ( i + 1 ) % 256
    j = ( j + S[i] ) % 256
    S[i] , S[j] = S[j] , S[i]
    out.append(chr(ord(char) ^ S[(S[i] + S[j]) % 256]))

print ''.join(out)

不确定这是否可行，因为您没有向我们提供任何可使用的数据。下次请发布数据示例、您已经尝试过的代码以及您遇到的错误。

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编辑——处理文件

import base64

with open("/path/to/file.txt", "r") as encrypted_file:
    data = base64.b64decode(encrypted_file.read())
key = "<rc4 key>"

S = range(256)
j = 0
out = []

#KSA Phase
for i in range(256):
    j = (j + S[i] + ord( key[i % len(key)] )) % 256
    S[i] , S[j] = S[j] , S[i]

#PRGA Phase
i = j = 0
for char in data:
    i = ( i + 1 ) % 256
    j = ( j + S[i] ) % 256
    S[i] , S[j] = S[j] , S[i]
    out.append(chr(ord(char) ^ S[(S[i] + S[j]) % 256]))

decrypted_text = ''.join(out)
with open('decrypted.txt', 'w') as decrypted_file:
    decrypted_file.write(decrypted_text)

Answer 2

PyCryptodome 现在可以做到：https ://pycryptodome.readthedocs.io/en/latest/src/cipher/arc4.html

from Crypto.Cipher import ARC4
key = b'Very long and confidential key'
cipher = ARC4.new(key)
msg = cipher.encrypt(b'Open the pod bay doors, HAL')