Python to C# AES CBC PKCS7

Question

我正在尝试将这段C#代码转换成Python (2.5，GAE)。问题是，每次运行加密(在相同的字符串上)时，来自python脚本的加密字符串是不同的。

string Encrypt(string textToEncrypt, string passphrase)
 {
    RijndaelManaged rijndaelCipher = new RijndaelManaged();
    rijndaelCipher.Mode = CipherMode.CBC;
    rijndaelCipher.Padding = PaddingMode.PKCS7;

    rijndaelCipher.KeySize = 128;
    rijndaelCipher.BlockSize = 128;
    byte[] pwdBytes = Encoding.UTF8.GetBytes(passphrase);
    byte[] keyBytes = new byte[16];
    int len = pwdBytes.Length;
    if (len > keyBytes.Length)
    {
        len = keyBytes.Length;
    }
    Array.Copy(pwdBytes, keyBytes, len);
    rijndaelCipher.Key = keyBytes;
    rijndaelCipher.IV = new byte[16];
    ICryptoTransform transform = rijndaelCipher.CreateEncryptor();
    byte[] plainText = Encoding.UTF8.GetBytes(textToEncrypt);
    return Convert.ToBase64String(transform.TransformFinalBlock(plainText, 0, plainText.Length));
}

Python代码：(PKCS7Encoder：http://japrogbits.blogspot.com/2011/02/using-encrypted-data-between-python-and.html)

from Crypto.Cipher import AES
from pkcs7 import PKCS7Encoder
#declared outside of all functions
key = '####'
mode = AES.MODE_CBC
iv = '\x00' * 16
encryptor = AES.new(key, mode, iv)
encoder = PKCS7Encoder()

def function(self):
 text = self.request.get('passwordTextBox')
 pad_text = encoder.encode(text)
 cipher = encryptor.encrypt(pad_text)
 enc_cipher = base64.b64encode(cipher)

C#代码是继承的。Python代码必须以相同的方式进行加密和解密，以便C#代码能够正确地解码该值。

注:我是python的新手:)

编辑:对不起。应该区分有一个函数正在被调用。

谢谢!

Answer 1

您的C#代码无效。

Encrypt函数接受作为string passphrase的密码短语，然后尝试在byte[] pwdBytes = Encoding.UTF8.GetBytes(key);这一行中引用它

将key更改为passphrase。

这两个函数现在为我产生了相同的结果：

Python

secret_text = 'The rooster crows at midnight!'
key = 'A16ByteKey......'
mode = AES.MODE_CBC
iv = '\x00' * 16

encoder = PKCS7Encoder()
padded_text = encoder.encode(secret_text)

e = AES.new(key, mode, iv)
cipher_text = e.encrypt(padded_text)

print(base64.b64encode(cipher_text))

# e = AES.new(key, mode, iv)
# cipher_text = e.encrypt(padded_text)
# print(base64.b64encode(cipher_text))

C# (使用上面提到的拼写错误修复)

Console.WriteLine(Encrypt("The rooster crows at midnight!", "A16ByteKey......"));

Python结果

XAW5KXVbItrc3WF0xW175UJoiAfonuf+s54w2iEs+7A=

C#结果

XAW5KXVbItrc3WF0xW175UJoiAfonuf+s54w2iEs+7A=

我怀疑您在python代码中多次重复使用“e”。如果您取消注释我的python脚本的最后两行，您将看到现在的输出不同了。但是如果您取消对最后三行的注释，您将看到输出是相同的。正如Foon所说，这要归功于how CBC works。

当加密块中的字节序列时，CBC (密码块链接)起作用。第一个块通过将IV与明文的第一个字节(“公鸡...”)结合在一起进行加密。第二个块使用第一个操作的结果，而不是IV。

当您再次调用e.encrypt()时(例如，取消python脚本的最后两行的逗号)，您将从上次停止的地方继续。它将使用最后一个加密块的输出，而不是在加密第一个块时使用IV。这就是为什么结果看起来不同的原因。通过取消python脚本的最后三行的注释，您可以初始化一个新的加密器，该加密器将使用IV作为其第一个块，从而使您获得相同的结果。

Answer 2

将python代码更改为：

from Crypto.Cipher import AES
from pkcs7 import PKCS7Encoder
#declared outside of all functions
key = '####'
mode = AES.MODE_CBC
iv = '\x00' * 16
encoder = PKCS7Encoder()

def function(self):
 encryptor = AES.new(key, mode, iv)**
 text = self.request.get('passwordTextBox')
 pad_text = encoder.encode(text)
 cipher = encryptor.encrypt(pad_text)
 enc_cipher = base64.b64encode(cipher)

以防任何人通过google访问此页面

Answer 3

这个esotic PKCS7编码器是其他任何东西，而不是一个静态长度填充的函数。所以我用一个非常小的代码来实现它

#!/usr/bin/env python

from Crypto.Cipher import AES
import base64

# the block size for the cipher object; must be 16, 24, or 32 for AES
BLOCK_SIZE = 16

# the character used for padding--with a block cipher such as AES, the value
# you encrypt must be a multiple of BLOCK_SIZE in length.  This character is
# used to ensure that your value is always a multiple of BLOCK_SIZE

# PKCS7 method
PADDING = '\x06'
mode = AES.MODE_CBC
iv = '\x08' * 16 # static vector: dangerous for security. This could be changed periodically
# 

# one-liner to sufficiently pad the text to be encrypted
pad = lambda s: s + (BLOCK_SIZE - len(s) % BLOCK_SIZE) * PADDING

# one-liners to encrypt/encode and decrypt/decode a string
# encrypt with AES, encode with base64
EncodeAES = lambda c, s: base64.b64encode(c.encrypt(pad(s)))
DecodeAES = lambda c, e: c.decrypt(base64.b64decode(e)).rstrip(PADDING)



def CryptIt(password, secret):
    cipher = AES.new(secret, mode, iv)
    encoded = EncodeAES(cipher, password)
    return encoded

def DeCryptIt(encoded, secret):
    cipher = AES.new(secret, mode, iv)
    decoded = DecodeAES(cipher, encoded)
    return decoded

我希望这能有所帮助。干杯