PyCrypto 解密混乱

Question

所以我现在正在尝试在 Python 中制作一个简单的 AES encrypt/decrypt 系统...但是当它解密时它前面有一堆 /xxx/xxx/xxx/xxx/解密后的字符串。如何清理它并使其仅打印明文。

我的代码是：

import base64
from Crypto.Cipher import AES
from Crypto import Random

key = b'Sixteen byte key'
iv = Random.new().read(AES.block_size)
cipher = AES.new(key, AES.MODE_CFB, iv)
msg = iv + cipher.encrypt(b'Attack at dawn...')
print (msg)
print (base64.b64encode(msg))

print (cipher.decrypt(msg))

decrypt 的输出如下所示：

b'\xfb\xb8\xf0\xc3\xffH\xfc~\x19[\xecy?\xf8\xcc\x80Attack at dawn...'

Answer 1

docs状态：

That also means that you cannot reuse an object for encrypting or decrypting other data with the same key.

这有点神秘，但似乎意味着您不能重复使用 cipher 来解密。另外，我不确定您为什么将 iv 连接到您的加密邮件。

下面的代码对我来说很好用：

key = b'Sixteen byte key'
iv = Random.new().read(AES.block_size)
c = AES.new(key, AES.MODE_CFB, iv)
msg = c.encrypt('Attack at dawn...')
d = AES.new(key, AES.MODE_CFB, iv)
d.decrypt(msg)

Answer 2

初始化向量 (IV) 是加密消息 (msg) 的一部分，但密文本身应包含 IV。这意味着您必须在解密之前删除 IV，即像这样：

cipher.decrypt(msg[16:])

下一个问题是您不应该使用相同的 AES 实例进行加密和解密。 AES 实例包含无法轻易刷新的内部缓冲区。

key = b'Sixteen byte key'

# encryption
iv = Random.new().read(AES.block_size)
cipher = AES.new(key, AES.MODE_CFB, iv)
msg = iv + cipher.encrypt(b'Attack at dawn...')
print (msg)
print (base64.b64encode(msg))

# decryption
cipher = AES.new(key, AES.MODE_CFB, msg[:16])
print (cipher.decrypt(msg[16:]))

However when it decrypts it has a bunch of /xxx/xxx/xxx/xxx/ in front of the decrypted string.

您真幸运，在最后看到了解密后的字符串。这只是因为 IV 被添加到消息和 CFB 操作模式的内部工作原理之前。如果您使用 CTR 模式，这看起来会大不相同。

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