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Is it safe not to have a 2FA for a password manager itself?

It seems that using an app for TOTP authentication for a password manager could increase the security. But it turns out that in this case I should remember by heart the password for the TOTP authenticator also. If I change passwords according to common recommendations - every 1-2 months, I should have a very good memory to keep two passphrases in my head which change every month.

I always keep in mind the scenario where I lose physical access to all my devices - and have to recover it from scratch, from some clean device.

I also don't have any physical tokens - maybe the only right way is to acquire one?

2 Answers 2

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Password change policies are enforced to limit the amount of time an attacker can use a leaked password, or limit the amount of time an attacker have to crack a hash or decrypt it. As the vast majority of users reuse passwords, that protects a service against a leaked password from another service.

It does not help much when users just increment some numbers on the password to comply with the policy. So forcing users change the password every now and then without using a password manager is adding little security. It's adding something, but not much.

That does not apply to the master password for the password manager. That password should be very secure, long, and should never ever be reused anywhere. That password is the single point of failure. If it leaks, all accounts are compromised. If it get forgotten, you will have to reset all passwords.

If an attacker have your database file, it have unlimited time to crack the password, so changing the password of your copy does nothing to prevent that. Password managers should have a good encryption process protecting the database, so cracking a database should not be viable. LastPass was an example of what not to do. Bitwarden changed the default PBKDF2 difficulty in February, 2023. Look at your password manager settings to see how it is defined on yours.

If you are reusing your master password somewhere else, you are doing it wrong. So changing it from time to time will add nothing to the security of your database.

Adding a TOTP to the password manager would help, but little. If an attacker already have the master password, the strongest defense was already breached. If the database leaked, he can bruteforce the TOTP token and grab all passwords. Unless the password manager is a cloud-based online service, it would not help. (I don't trust my passwords to an online service. LastPass proved that an online service is a bad idea, so my password manager is offline, and only the encrypted database leaves my computer to sync with my other devices.)

I don't change my master password. It's very long, random, never used anywhere.

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You have asked two questions, one about 2FA for a password manager and the other about changing your password manager's master password regularly. It is good that you asked, because the master passwords for a well-designed password manager are subtly but importantly different than the overwhelming majority of passwords you've dealt.

I will take each in turn.

2FA doesn't do much good without authentication

Depending on the design of the password manager, 2FA may merely be security theater. A password manager that is built primarily or solely around encrypting your data does not depend on authentication. That is, your master password is an encryption password not an authentication password. So there isn't really much gain is strengthening the authentication process.

If your encrypted data is not stored locally so that authentication is required to retrieve the data, then adding a second factor to the authentication process can be useful. But if setting up 2FA for your password manager leads you to believe that you can use a weaker master password than you otherwise would, 2FA would do far more damage than good.

Changing master passwords

The security properties of a password used for authentication (like almost every password you have ever dealt with) and a password used for encryption (like with a well-designed password manager) differ in ways that can have a profound effect on what changing the password means.

Quite simply changing an encryption password doesn't prevent an attacker with an older copy of your encrypted data from decrypting it with the old password. So your backups can still be decrypted with the old password. Furthermore, decrypting an old backup with an old password may also reveal encryption keys that can be used to decrypt data encrypted even after the master password change.

So regularly changing a password manager master password does even less good than regularly changing an authentication password, but it does even more harm. So you are actually creating more ways into your data every time you change your password manager master password.

Why are they built this way?

The above two differences between typical passwords (used for authentication) and passwords used for encryption would seem to make authentication passwords a better choice. Multiple authentication factors can be used to improve the security of authentication based systems, and password changes of passwords used for authentication have the desired and expected security properties. The developers of password managers know those advantages of authentication over encryption. Yet they still decide to use encryption in their design. Why?

If password managers relied solely on authentication then the operator of the system would have full access to your secrets. And not just the operator of that system, but anyone who compromised the system where your passwords were stored would have complete access to everyone's password. But if only you have the secrets necessary to decrypt your passwords then it really and truly is the case that only you can see your secrets.

Not all password managers are the same. I have focused on encryption-based ones. Some of them do ofter 2FA as security theater, while others offer 2FA only where there genuinely is a meaningful authentication component. Some incorporate designs which try to mitigate some of the shortcomings of passwords for encryption with additional complexity of design. So the details will vary, but in general regular password changes are even worse for password manager master passwords than for authentication passwords and MFA will do even less for password manager master passwords than it does for authentication passwords.

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