如何确保 Fernet 密钥在初始化时保持不变？

Question

所以，我正在制作一个密码管理器，并且我正在使用密码学模块。该程序的问题在于解密时。当我在同一个会话中加密和解密时它会正常工作，但是当我在不同的会话中加密、关闭然后解密时，会引发错误。这个错误没有发生，因为我每次都生成一个随机密钥，但我认为当我使用 Fernet() 方法初始化它时，密钥正在改变。我该如何解决？

#The Dependicies and Packages required for this script
import sqlite3 
from cryptography.fernet import Fernet


def generate_key():
    """
    Generates a key and save it into a file
    """
    key = Fernet.generate_key()
    with open("secret.key", "wb") as key_file:
        key_file.write(key)


def load_key():
    """
    Loads the key named `secret.key` from the current directory.
    """
    return open("secret.key", "rb").read()

#These are the keys for encryption
Key = load_key()

f = Fernet(Key)


def decode_data(datas):
    new_name = f.decrypt(datas)
    final_name = new_name.decode()
    return final_name 
def find_password():
    """
    This function is to get the password of the website that the user expected
    """
    website_name = input("What is the website's name for which you need a password>")
    c.execute("SELECT * FROM passwords")
    data = c.fetchall()
    print(data)
    for row in data:
        print(row[0])
        name = decode_data(row[0])
        if name == website_name:
            password = decode_data(row[2])
            print(f'The password to {website_name} is {password}')


def main():
    go_on = True
    while go_on:
        direction_question = input("This is your password manager. Press 1 to create a new pasword, Press 2 to search for a password, or Press 3 to exit the program>")
        if direction_question.lower() == "1":
            create_password()
        if direction_question.lower() == "2":
            find_password()
        if direction_question.lower() == "3":
            go_on = False
        else:
            print("Invalid response")
    db.commit()
    db.close()


if __name__ == "__main__":
    db = sqlite3.connect('password.db')
    c = db.cursor()
    main()

引发了这些错误

  File "/usr/local/lib/python3.7/site-packages/cryptography/fernet.py", line 114, in _verify_signature
    h.verify(data[-32:])
  File "/usr/local/lib/python3.7/site-packages/cryptography/hazmat/primitives/hmac.py", line 68, in verify
    ctx.verify(signature)
  File "/usr/local/lib/python3.7/site-packages/cryptography/hazmat/backends/openssl/hmac.py", line 78, in verify
    raise InvalidSignature("Signature did not match digest.")
cryptography.exceptions.InvalidSignature: Signature did not match digest.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "password_manager.py", line 86, in <module>
    main()
  File "password_manager.py", line 74, in main
    find_password()
  File "password_manager.py", line 61, in find_password
    name = decode_data(row[0])
  File "password_manager.py", line 28, in decode_data
    new_name = f.decrypt(datas)
  File "/usr/local/lib/python3.7/site-packages/cryptography/fernet.py", line 77, in decrypt
    return self._decrypt_data(data, timestamp, ttl, int(time.time()))
  File "/usr/local/lib/python3.7/site-packages/cryptography/fernet.py", line 126, in _decrypt_data
    self._verify_signature(data)
  File "/usr/local/lib/python3.7/site-packages/cryptography/fernet.py", line 116, in _verify_signature
    raise InvalidToken
cryptography.fernet.InvalidToken

Answer 1

您已经将生成的密钥存储到单独的文件中做得很好。我已经运行了您的脚本，它工作正常。我发现的唯一问题是以下部分应该在main() 方法内。

Key = load_key() 
f = Fernet(Key)

由于main() 方法实际上是获取一个空字符串作为密钥，而不是读取.key 文件中存储的密钥。因此，它正在抛出

raise InvalidSignature("签名与摘要不匹配。")

cryptography.exceptions.InvalidSignature：签名与摘要不匹配。

和

提高 InvalidToken

cryptography.fernet.InvalidToken