This post is long and kind of a rant. I don't expect many to read the whole thing, but there's a conclusion at the bottom.
On the surface, recommended security practices are simple:
- Store all your credentials in a password manager
- Use two factor authentication on all accounts
However, it raises a few questions.
- Should you access your 2FA codes on the same device as the password manager?
- Should you store them in the password manager itself?
This is the beginning of where a threat model is needed. If your threat model does not include protections against unwanted access to your device, it is safe for you to store access your 2FA codes on the same device as your password manager, or even in the password manager itself.
So, to keep it simple, say you store your 2FA in your password manager. There's a few more questions:
- Where do you store the master password for the password manager?
- Where do you store 2FA recovery codes?
The master password for the password manager could be written down on a piece of paper and stored in a safe, but that would be inconvenient when you want to access your passwords. So, a better solution is to just remember your password. Passphrases are easier to remember than passwords, so we'll use one of those.
Your 2FA recovery codes are something that are needed if you lose access to your real 2FA codes. Most websites just say "Store this in a secure place". This isn't something you want to store in the same place as those (in this case our password manager), and it's not something you will access often, so it's safe to write it down on a piece of paper and lock it in a safe.
Good so far, you have a fairly simple system to keep your accounts safe from some threats. But, new problems arise:
- What happens if you forget your master passphrase?
- What happens if others need access to your password manager?
The problem with remembering your passphrase is that it's possible to forget it, no matter how many times you repeat it to yourself. Besides naturally forgetting it, things like injuries can arise which can cause you to forget the passphrase. Easy enough to fix, though. We can just keep a copy of the passphrase in the safe, just in case we forget it.
If someone else needs to access certain credentials in your password manager, for example a wife that needs to verify bank information using your account, storing a copy of the password is a good idea here too. Since she is a trusted party, you can give her access to the safe in case of emergencies.
The system we have is good. If the safe is stolen or destroyed, you still have the master passphrase memorized to change the master passphrase and regenerate the 2FA security codes. The thief who stole the safe doesn't have your password manager's data, so the master passphrase is useless. However, our troubles aren't over yet:
- How do you store device credentials?
- How do you keep the password manager backed up?
Your password manager has to have some device in order to access it. Whether it's a phone, computer, tablet, laptop, or website, there needs to be some device used to access it. That device needs to be as secure as your password manager, otherwise accessing the password manager becomes a risk. This means using full disk encryption for the device, and a strong login passphrase. However, that means we have 2 more passwords to take care of that can't be stored in the password manager. We access those often, so we can't write them down and store them in the safe, Remembering two more passphrases complicates things and makes forgetting much more likely. Where do we store those passphrases?
One solution is removing the passwords altogether. Using a hardware security key, you can authenticate your disk encryption and user login using it. If you keep a spare copy of the security key stored in the safe, you make sure you aren't locked out if you lose access to your main security key.
Now to keep the password manager backed up. Using the 3-2-1 Backup Strategy. It states that there should be at least 3 copies of the data, stored on 2 different types of storage media, and one copy should be kept offsite, in a remote location (this can include cloud storage). 2 or more different media should be used to eliminate data loss due to similar reasons (for example, optical discs may tolerate being underwater while LTO tapes may not, and SSDs cannot fail due to head crashes or damaged spindle motors since they do not have any moving parts, unlike hard drives). An offsite copy protects against fire, theft of physical media (such as tapes or discs) and natural disasters like floods and earthquakes. Physically protected hard drives are an alternative to an offsite copy, but they have limitations like only being able to resist fire for a limited period of time, so an offsite copy still remains as the ideal choice.
So, our first copy will be on our secure device. It's the copy we access the most. The next copy could be an encrypted hard drive. The encryption passphrase could be stored in our safe. The last copy could be a cloud storage service. Easy, right? Well, more problems arise:
- Where do you store the credentials for the cloud storage service?
- Where do you store the LUKS backup file and password?
Storing the credentials for the cloud storage service isn't as simple as putting it in the safe. If we did that, then anyone with the safe could login to the cloud storage service and decrypt the password manager backup using the passphrase also stored in the safe. If we protected the cloud storage service with our security key, a copy of that is still in the safe. Maybe we protect it with a 2FA code, and instead of storing the 2FA codes in the password manager, we store it on another device. That solves the problem for now, but there are still problems, such as storing the credentials for that new device.
When using a security key to unlock a LUKS partition, you are given a backup file to store as a backup for emergencies. Plus, LUKS encrypted partitions still require you to setup a passphrase, so storing that still becomes an issue.
Conclusion
I'm going to stop here, because this post is getting long. I could keep going fixing problems and causing new ones, but the point is this: Security is a mess! I didn't even cover alternative ways to authenticate the password manager such as a key file, biometrics, etc. Trying to find "perfect" security is almost impossible, and that's why a threat model is important. If you set hard limits such as "No storing passwords digitally" or "No remembering any passwords" then you can build a security system that fits that threat model, but there's currently no security system that fits all threat model.
However, that doesn't let companies that just say "Store this in a secure place" off the hook either. It's a hand wavy response to security that just says "We don't know how to secure this part of our system, so it's your problem now". We need to have comprehensive security practices that aren't just "Use a password manager and 2FA", because that causes people to just store their master passphrase on a sticky note or a text file on the desktop.
The state of security is an absolute mess, and I'm sick of it. It seems that, right now, security, privacy, convenience, and safety (e.g. backups, other things that remove single points of failure) are all at odds with each other. This post mainly focused on how security, convenience, and safety are at odds, but I could write a whole post about how security and privacy are at odds.
Anyways, I've just outlined one possible security system you can have. If you have one that you think works well, I'd like to hear about it. I use a different security system than what I outline here, and I see problems with it.
Thanks for reading!