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Comment by wannacboatmovie | Hacker News Reader

BitLocker and LUKS both support TPM for key storage which VeraCrypt does not.

The TPM acts as a second factor (assume PIN is required); if you pulled the disk out and placed it another PC you cannot brute force the plaintext password, even using the $5 wrench method.

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I would be very careful with placing my trust in TPM: https://www.secura.com/blog/tpm-sniffing-attacks-against-non....

Your parent comment said he was assuming a PIN was used to seal the TPM, and the attacking the link would have failed if the TPM had a PIN set, no? I agree though that using a TPM without a PIN gives little in the way of data protection. Not nothing, but little.

Sniffing the bus can be defeated by using encrypted comms. It is disabled by Windows for some reason, but it works as designed in other secure boot implementations. I hope :)

> even using the $5 wrench method

I understand the XKCD reference but I don't understand why it does not apply to this case. Does that mean that you can't move your disk to a new machine of yours?

Because if you took the disk, even if you $5-wrenched the pin out of someone, you don't have the TPM hardware to make use of it.

As for the second question, I suppose it depends on the implementation; I suspect there is a way to migrate and transfer the keys for the device for the person who already has access to all of the factors.

If I use a Yubikey and LUKS for example, I can re-use the Yubikey if I move the disk to another machine. I'm not sure how this would work for integrated TPMs and Bitlocker (I don't use Windows), but I believe they have recovery key-files you could use.

If there is no way to transfer the disk to another machine, it's not a disk I want to use. I think that there are very few use cases for losing all the data when a machine dies.

And if there is a procedure to let me move the disk to a new machine, somebody can wrench me until I perform that procedure for them.

For Bitlocker (and I imagine other tools which support TPM keying), a recovery password is generated in addition to the TPM unlock key. If the motherboard goes kaput you dig out the long key to unlock it, assuming you kept it somewhere safe (speaking as someone who has had to dig through a pile of old USBs to get access back to a disk).

Sounds as though this is where the $5 wrench would work just fine.

It's a matter of priorities, I guess?

If you want to you can just not save the recovery password. In that case I guess they'll just beat you to death with that $5 wrench.

That's why I'd rather use a service without a recovery password :)

With LUKS you can enroll an extra auth option in addition to TPM, like a password or a FIDO2 token.

> And if there is a procedure to let me move the disk to a new machine, somebody can wrench me until I perform that procedure for them.

I think the implication is that they (the attacker) don't have the machine, or you, or whatever "thing" you have/use to unlock it.

If someone stole your disk, or took a copy of it, they can't offline attack it.

An external hardware device seems preferable for this scenario; if someone steals/snatches your laptop, they won't have your Yubikey or whatever.

In any scenario where the wrenching is an option, I suspect all bets are off, but if wrenching is a real risk, and whatever you're protecting is worth taking a wrenching for (as opposed to just giving it up at the threat of a wrenching), there should probably be some tougher protections which make it clear that the wrenching will gain an attacker nothing, and hopefully save you from it to begin with.

I'm not sure what or how that would work.

> Because if you took the disk, even if you $5-wrenched the pin out of someone, you don't have the TPM hardware to make use of it.

I sincerely hope that the guy with the $5 wrench knows this and don't continue hitting until he has the key...

Indeed, it seems that having another unlock option might be preferable. If you value your own live over the secrets, that is.

does that mean if morherboard goes kaput, so does all my data? I have 7 layers of backup, but still interesting to know.

No, it typically generates a recovery key which you can keep offline (or discard and live dangerously).

ok, so the $5 wrench method can be used to extract the recovery key.

You typically print it and store it in a safe place (like your home cabinet). It's something like 256bit random number, no way to recall it, especially while being subjected to the $5 wrench method.

No need to recall 256 bits, just which cabinet.

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