我将如何生成可重复的加密密钥？

Question

I need to sent my friend Bob the number 42, my code will use a pre-shared key generate a random number to encrypt the message (42) and decrypt it on Bobs end. the only problem is, I have no clue how to generate a repeatable encryption key in python.

Answer 1

You can use Crypto to encrypt a message using AES.

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

class AESCipher():
    def __init__(self, key):
        self.private_key = hashlib.sha256(key.encode()).digest()
        self.bs = AES.block_size

    def encrypt(self, data):
        # generate public key
        public_key = Random.new().read(self.bs)

        # setup AES Cipher using public key and private key
        cipher = AES.new(self.private_key, AES.MODE_CBC, public_key)

        # enrpyt the data and convert to base64
        return base64.b64encode(public_key + cipher.encrypt(self.pad(data).encode()))

    def decrypt(self, enc):
        # convert encrypted data to base 64
        enc = base64.b64decode(enc)

        # get public key
        public_key = enc[:AES.block_size]

        # setup AES Cipher using public and private key
        cipher = AES.new(self.private_key, AES.MODE_CBC, public_key)

        # decrypt data using the public key
        return self.unpad(cipher.decrypt(enc[AES.block_size:])).decode("utf-8")

    def pad(self, s):
        # pads data so that it's a multiple of 16
        return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)

    def unpad(self, s):
        # removes padding
        return s[:-ord(s[len(s)-1:])]

cipher = AESCipher("your secret key")

Here I encrypt some text, the public key with the encrypted text is joined and returned from the encrypt method, you can then send the returned text to Bob, to decrypt the text bob then just needs to run the decrypt method.

>>> cipher.encrypt("your message")
b'HYfUkcd//CaRquG9AhReR8bJYdVQdcGWRAjcp9AstLs='
>>> output = cipher.encrypt("your message")
>>> output
b'RVTK7L7ZDw9DzvuXuj8zYPZJjBO/A0N3l5N1hp9LY6U='
>>> cipher.decrypt(output)
'your message'
>>>