对称加密python代码实现

对称加密是一种常用的加密技术，其中使用相同的密钥（secret key）进行加密和解密数据。Python中有多种库可以用于对称加密，如`cryptography`库。下面是一个简单的AES（Advanced Encryption Standard）对称加密的示例：

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

# 加密函数
def encrypt(plaintext, key):
    backend = default_backend()
    cipher_suite = Cipher(algorithms.AES(key), modes.ECB(), backend=backend)
    encryptor = cipher_suite.encryptor()  # 创建加密器
    ciphertext = encryptor.update(plaintext) + encryptor.finalize()  # 加密数据
    return ciphertext

# 解密函数
def decrypt(ciphertext, key):
    backend = default_backend()
    cipher_suite = Cipher(algorithms.AES(key), modes.ECB(), backend=backend)
    decryptor = cipher_suite.decryptor()  # 创建解密器
    plaintext = decryptor.update(ciphertext) + decryptor.finalize()  # 解密数据
    return plaintext.decode('utf-8')  # 将字节转换回字符串（假设输入的是UTF-8编码）

# 示例
key = b'sixteen_byte_key'  # 16字节的AES密钥
plaintext = "This is a secret message"
ciphertext = encrypt(plaintext.encode('utf-8'), key)
print("Encrypted:", ciphertext)
decrypted_text = decrypt(ciphertext, key)
print("Decrypted:", decrypted_text)