让我来回答你关于“模式”的问题。AES-256是一种分组密码。它以一个32字节的键和一个16字节的字符串(称为块)作为输入，并输出一个块。为了加密，我们在操作模式中使用AES。上面的解决方案建议使用CBC，这是一个例子。另一种叫做CTR，它更容易使用:

from Crypto.Cipher import AES
from Crypto.Util import Counter
from Crypto import Random

# AES supports multiple key sizes: 16 (AES128), 24 (AES192), or 32 (AES256).
key_bytes = 32

# Takes as input a 32-byte key and an arbitrary-length plaintext and returns a
# pair (iv, ciphtertext). "iv" stands for initialization vector.
def encrypt(key, plaintext):
    assert len(key) == key_bytes

    # Choose a random, 16-byte IV.
    iv = Random.new().read(AES.block_size)

    # Convert the IV to a Python integer.
    iv_int = int(binascii.hexlify(iv), 16)

    # Create a new Counter object with IV = iv_int.
    ctr = Counter.new(AES.block_size * 8, initial_value=iv_int)

    # Create AES-CTR cipher.
    aes = AES.new(key, AES.MODE_CTR, counter=ctr)

    # Encrypt and return IV and ciphertext.
    ciphertext = aes.encrypt(plaintext)
    return (iv, ciphertext)

# Takes as input a 32-byte key, a 16-byte IV, and a ciphertext, and outputs the
# corresponding plaintext.
def decrypt(key, iv, ciphertext):
    assert len(key) == key_bytes

    # Initialize counter for decryption. iv should be the same as the output of
    # encrypt().
    iv_int = int(iv.encode('hex'), 16)
    ctr = Counter.new(AES.block_size * 8, initial_value=iv_int)

    # Create AES-CTR cipher.
    aes = AES.new(key, AES.MODE_CTR, counter=ctr)

    # Decrypt and return the plaintext.
    plaintext = aes.decrypt(ciphertext)
    return plaintext

(iv, ciphertext) = encrypt(key, 'hella')
print decrypt(key, iv, ciphertext)

这通常被称为AES-CTR。我建议谨慎使用AES-CBC与PyCrypto。原因是它要求您指定填充方案，正如给出的其他解决方案所示。一般来说，如果不小心填充，就会出现完全破坏加密的攻击!

现在，重要的是要注意键必须是一个随机的32字节字符串;密码是不够的。通常，键的生成是这样的:

# Nominal way to generate a fresh key. This calls the system's random number
# generator (RNG).
key1 = Random.new().read(key_bytes)

密钥也可以由密码派生:

# It's also possible to derive a key from a password, but it's important that
# the password have high entropy, meaning difficult to predict.
password = "This is a rather weak password."

# For added # security, we add a "salt", which increases the entropy.
#
# In this example, we use the same RNG to produce the salt that we used to
# produce key1.
salt_bytes = 8
salt = Random.new().read(salt_bytes)

# Stands for "Password-based key derivation function 2"
key2 = PBKDF2(password, salt, key_bytes)

上面的一些解决方案建议使用SHA-256来获得密钥，但这通常被认为是糟糕的加密实践。 查看维基百科了解更多操作模式。

你可以通过使用像SHA-1或SHA-256这样的加密哈希函数(不是Python的内置哈希)从任意密码中获得密码短语。Python在其标准库中包含了对这两者的支持:

import hashlib

hashlib.sha1("this is my awesome password").digest() # => a 20 byte string
hashlib.sha256("another awesome password").digest() # => a 32 byte string

您可以使用[:16]或[:24]截断加密哈希值，它将保留其安全性，直到您指定的长度。

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

BLOCK_SIZE=16
def trans(key):
     return md5.new(key).digest()

def encrypt(message, passphrase):
    passphrase = trans(passphrase)
    IV = Random.new().read(BLOCK_SIZE)
    aes = AES.new(passphrase, AES.MODE_CFB, IV)
    return base64.b64encode(IV + aes.encrypt(message))

def decrypt(encrypted, passphrase):
    passphrase = trans(passphrase)
    encrypted = base64.b64decode(encrypted)
    IV = encrypted[:BLOCK_SIZE]
    aes = AES.new(passphrase, AES.MODE_CFB, IV)
    return aes.decrypt(encrypted[BLOCK_SIZE:])

我用过Crypto和PyCryptodomex库，它非常快…

import base64
import hashlib
from Cryptodome.Cipher import AES as domeAES
from Cryptodome.Random import get_random_bytes
from Crypto import Random
from Crypto.Cipher import AES as cryptoAES

BLOCK_SIZE = AES.block_size

key = "my_secret_key".encode()
__key__ = hashlib.sha256(key).digest()
print(__key__)

def encrypt(raw):
    BS = cryptoAES.block_size
    pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
    raw = base64.b64encode(pad(raw).encode('utf8'))
    iv = get_random_bytes(cryptoAES.block_size)
    cipher = cryptoAES.new(key= __key__, mode= cryptoAES.MODE_CFB,iv= iv)
    a= base64.b64encode(iv + cipher.encrypt(raw))
    IV = Random.new().read(BLOCK_SIZE)
    aes = domeAES.new(__key__, domeAES.MODE_CFB, IV)
    b = base64.b64encode(IV + aes.encrypt(a))
    return b

def decrypt(enc):
    passphrase = __key__
    encrypted = base64.b64decode(enc)
    IV = encrypted[:BLOCK_SIZE]
    aes = domeAES.new(passphrase, domeAES.MODE_CFB, IV)
    enc = aes.decrypt(encrypted[BLOCK_SIZE:])
    unpad = lambda s: s[:-ord(s[-1:])]
    enc = base64.b64decode(enc)
    iv = enc[:cryptoAES.block_size]
    cipher = cryptoAES.new(__key__, cryptoAES.MODE_CFB, iv)
    b=  unpad(base64.b64decode(cipher.decrypt(enc[cryptoAES.block_size:])).decode('utf8'))
    return b

encrypted_data =encrypt("Hi Steven!!!!!")
print(encrypted_data)
print("=======")
decrypted_data = decrypt(encrypted_data)
print(decrypted_data)

对于想要使用urlsafe_b64encode和urlsafe_b64decode的人，这里是为我工作的版本(在花了一些时间与unicode问题之后)

BS = 16
key = hashlib.md5(settings.SECRET_KEY).hexdigest()[:BS]
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[:-ord(s[len(s)-1:])]

class AESCipher:
    def __init__(self, key):
        self.key = key

    def encrypt(self, raw):
        raw = pad(raw)
        iv = Random.new().read(AES.block_size)
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return base64.urlsafe_b64encode(iv + cipher.encrypt(raw)) 

    def decrypt(self, enc):
        enc = base64.urlsafe_b64decode(enc.encode('utf-8'))
        iv = enc[:BS]
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return unpad(cipher.decrypt(enc[BS:]))

PyCrypto已经过时了。

如今，密码学有了更好的支持。

这是另一个实现。注意，这将返回字节，您需要使用base64将它们转换为用于传输的字符串。

import os
import hashlib
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend

_BLOCK_SIZE = 16

class AesStringCipher:
    def __init__(self, key):
        self._key = hashlib.sha256(key.encode()).digest()

    def encrypt_str(self, raw:str) -> bytes:
        iv = os.urandom(_BLOCK_SIZE)
        cipher = Cipher(algorithms.AES(self._key), modes.CBC(iv), default_backend())
        encryptor = cipher.encryptor()
        raw = _pad(raw)
        return iv + encryptor.update(raw.encode('utf-8')) + encryptor.finalize()

    def decrypt_str(self, enc:bytes) -> str:
        iv = enc[:_BLOCK_SIZE]
        enc = enc[_BLOCK_SIZE:]
        cipher = Cipher(algorithms.AES(self._key), modes.CBC(iv), default_backend())
        decryptor = cipher.decryptor()
        raw = decryptor.update(enc) + decryptor.finalize()
        raw = raw.decode('utf-8')
        return _unpad(raw)

def _pad(s:str) -> str:
    padding = (_BLOCK_SIZE - (len(s) % _BLOCK_SIZE))
    return s + padding * chr(padding)

def _unpad(s:str) -> str:
    return s[:-ord(s[len(s)-1:])]


if __name__ == '__main__':
    cipher = AesStringCipher('my secret password')

    secret_msg = 'this is a super secret msg ...'
    enc_msg = cipher.encrypt_str(secret_msg)
    dec_msg = cipher.decrypt_str(enc_msg)

    assert secret_msg == dec_msg