from cryptography.fernet import Fernet

def load_key(key_file_path):
    # 从文件中加载对称密钥
    with open(key_file_path, 'rb') as key_file:
        key = key_file.read()
    return key

def decrypt_file(encrypted_file_path, key):
    with open(encrypted_file_path, 'rb') as encrypted_file:
        ciphertext = encrypted_file.read()

    cipher_suite = Fernet(key)
    plaintext = cipher_suite.decrypt(ciphertext)

    decrypted_file_path = encrypted_file_path.replace('.encrypted', '_decrypted.txt')
    with open(decrypted_file_path, 'wb') as decrypted_file:
        decrypted_file.write(plaintext)
    print('解密成功:' + decrypted_file_path)