Question

我已经有了一个工作程序，但唯一不起作用的是decrypt_file()函数。我仍然可以从文件中复制加密文本并将其放在我的decrypt()函数中并使其正常工作，但是当我尝试使用我应该使用的方便decrypt_file()函数时，它会抛出错误。现在我知道99.999％肯定我的encrypt()和decrypt()函数很好，但是当我读取并编码抛出错误的文本文件时，会有字节和字符串转换的内容;我只是找不到挂断。请帮忙！

我的计划：

from Crypto import Random
from Crypto.Cipher import AES

def encrypt(message, key=None, key_size=256):
    def pad(s):
        x = AES.block_size - len(s) % AES.block_size
        return s + ((bytes([x])) * x)

    padded_message = pad(message)

    if key is None:
        key = Random.new().read(key_size // 8)

    iv = Random.new().read(AES.block_size)
    cipher = AES.new(key, AES.MODE_CBC, iv)

    return iv + cipher.encrypt(padded_message)

def decrypt(ciphertext, key):
    unpad = lambda s: s[:-s[-1]]
    iv = ciphertext[:AES.block_size]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = unpad(cipher.decrypt(ciphertext))[AES.block_size:]

    return plaintext

def encrypt_file(file_name, key):
    f = open(file_name, 'r')
    plaintext = f.read()
    plaintext = plaintext.encode('utf-8')
    enc = encrypt(plaintext, key)
    f.close()
    f = open(file_name, 'w')
    f.write(str(enc))
    f.close()

def decrypt_file(file_name, key):
    def pad(s):
        x = AES.block_size - len(s) % AES.block_size
        return s + ((str(bytes([x]))) * x)

    f = open(file_name, 'r')
    plaintext = f.read()
    x = AES.block_size - len(plaintext) % AES.block_size
    plaintext += ((bytes([x]))) * x
    dec = decrypt(plaintext, key)
    f.close()
    f = open(file_name, 'w')
    f.write(str(dec))
    f.close()



key = b'\xbf\xc0\x85)\x10nc\x94\x02)j\xdf\xcb\xc4\x94\x9d(\x9e[EX\xc8\xd5\xbfI{\xa2$\x05(\xd5\x18'

encrypt_file('to_enc.txt', key)

我加密的文本文件：

b';c\xb0\xe6Wv5!\xa3\xdd\xf0\xb1\xfd2\x90B\x10\xdf\x00\x82\x83\x9d\xbc2\x91\xa7i M\x13\xdc\xa7'

尝试decrypt_file时出现错误：

    Traceback (most recent call last):
  File "C:\Python33\testing\test\crypto.py", line 56, in <module>
    decrypt_file('to_enc.txt', key)
  File "C:\Python33\testing\test\crypto.py", line 45, in decrypt_file
    plaintext += ((bytes([x]))) * x
TypeError: Can't convert 'bytes' object to str implicitly
[Finished in 1.5s]

当我用plaintext += ((str(bytes([x])))) * x替换第45行时，这是我得到的错误：

Traceback (most recent call last):
  File "C:\Python33\testing\test\crypto.py", line 56, in <module>
    decrypt_file('to_enc.txt', key)
  File "C:\Python33\testing\test\crypto.py", line 46, in decrypt_file
    dec = decrypt(plaintext, key)
  File "C:\Python33\testing\test\crypto.py", line 23, in decrypt
    plaintext = unpad(cipher.decrypt(ciphertext))[AES.block_size:]
  File "C:\Python33\lib\site-packages\Crypto\Cipher\blockalgo.py", line 295, in decrypt
    return self._cipher.decrypt(ciphertext)
ValueError: Input strings must be a multiple of 16 in length
[Finished in 1.4s with exit code 1]

Answer 1

我仔细研究了你的代码，发现它有几个问题。第一个是加密函数带有字节而不是文本。因此，最好将数据保存为字节字符串。只需在模式中输入“b”字符即可完成此操作。这样你就可以摆脱你想要做的所有编码和字节转换。

我还使用较新的Python习语重写了整个代码。在这里。

#!/usr/bin/python3

from Crypto import Random
from Crypto.Cipher import AES

def pad(s):
    return s + b"\0" * (AES.block_size - len(s) % AES.block_size)

def encrypt(message, key, key_size=256):
    message = pad(message)
    iv = Random.new().read(AES.block_size)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    return iv + cipher.encrypt(message)

def decrypt(ciphertext, key):
    iv = ciphertext[:AES.block_size]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = cipher.decrypt(ciphertext[AES.block_size:])
    return plaintext.rstrip(b"\0")

def encrypt_file(file_name, key):
    with open(file_name, 'rb') as fo:
        plaintext = fo.read()
    enc = encrypt(plaintext, key)
    with open(file_name + ".enc", 'wb') as fo:
        fo.write(enc)

def decrypt_file(file_name, key):
    with open(file_name, 'rb') as fo:
        ciphertext = fo.read()
    dec = decrypt(ciphertext, key)
    with open(file_name[:-4], 'wb') as fo:
        fo.write(dec)


key = b'\xbf\xc0\x85)\x10nc\x94\x02)j\xdf\xcb\xc4\x94\x9d(\x9e[EX\xc8\xd5\xbfI{\xa2$\x05(\xd5\x18'

encrypt_file('to_enc.txt', key)
#decrypt_file('to_enc.txt.enc', key)

Answer 2

在Python 3中（您正在使用），您打开的文件的默认模式是文本，而不是二进制文件。从文件中读取时，您将获得字符串而不是字节数组。这不符合加密。

在您的代码中，您应该替换：

open(file_name, 'r')

使用：

open(file_name, 'rb')

当您打开文件进行书写时也一样。此时，您可以摆脱从字符串转换为二进制的所有各种情况，反之亦然。

例如，这可能会消失：

plaintext = plaintext.encode('utf-8')

Python PyCrypto使用AES加密/解密文本文件

2 个答案: