python实现aes256加解密代码

以下是Python实现AES256加解密的代码示例：

from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad
from Crypto.Random import get_random_bytes

# 加密函数
def encrypt_AES256(key, plaintext):
    iv = get_random_bytes(16)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    ciphertext = cipher.encrypt(pad(plaintext.encode('utf-8'), AES.block_size))
    return iv + ciphertext

# 解密函数
def decrypt_AES256(key, ciphertext):
    iv = ciphertext[:16]
    ciphertext = ciphertext[16:]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = unpad(cipher.decrypt(ciphertext), AES.block_size)
    return plaintext.decode('utf-8')

# 测试代码
key = get_random_bytes(32) # 生成256位随机密钥
plaintext = "Hello World!"
ciphertext = encrypt_AES256(key, plaintext)
print("加密后的密文：", ciphertext)
decrypted_plaintext = decrypt_AES256(key, ciphertext)
print("解密后的明文：", decrypted_plaintext)

注意：以上代码依赖于`pycryptodome`库，需要先安装该库。