python aes文件加解密算法

在Python中，我们可以使用第三方库`cryptography`来进行AES（高级加密标准）文件的加解密操作。以下是基本步骤：

1. **安装依赖**：
首先需要通过pip安装`cryptography`库：

   pip install cryptography

2. **导入模块**：

   from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
   from cryptography.hazmat.backends import default_backend
   from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
   from os import urandom

3. **生成密钥和初始向量（IV）**：

   password = b'some_password'
   salt = urandom(16)  # 可选，用于增强安全性的随机盐
   kdf = PBKDF2HMAC(algorithm=algorithms.HMAC(algorithm=hashes.SHA256(), length=32), 
                   salt=salt, length=32, iterations=100000, backend=default_backend())
   key = kdf.derive(password)
   iv = urandom(16)  # AES-CTR模式下需要

4. **加密文件**：

   def encrypt_file(file_path, output_path, key, iv):
       cipher = Cipher(algorithms.AES(key), modes.CTR(iv), backend=default_backend())
       encryptor = cipher.encryptor()
       with open(file_path, 'rb') as in_file:
           with open(output_path, 'wb') as out_file:
               for chunk in iter(lambda: in_file.read(24), b""):
                   encrypted_data = encryptor.update(chunk)
                   out_file.write(encrypted_data)
       out_file.write(encryptor.finalize())  # 写入最终的填充块

5. **解密文件**：

   def decrypt_file(input_path, output_path, key, iv):
       cipher = Cipher(algorithms.AES(key), modes.CTR(iv), backend=default_backend())
       decryptor = cipher.decryptor()
       with open(input_path, 'rb') as in_file:
           with open(output_path, 'wb') as out_file:
               while True:
                   encrypted_chunk = in_file.read(24)
                   if not encrypted_chunk:
                       break
                   decrypted_data = decryptor.update(encrypted_chunk)
                   out_file.write(decrypted_data)
       out_file.write(decryptor.finalize())  # 写入解密后的数据

6. **示例用法**：

   encrypt_file('input.txt', 'output.enc', key, iv)
   decrypt_file('output.enc', 'output_dec.txt', key, iv)