2 ms·

The interesting thing about whole disk encryption is that it is not really breakable if a reasonably long password/phrase is used. Using a TPM adds a huge attac

The interesting thing about whole disk encryption is that it is not really breakable if a reasonably long password/phrase is used. Using a TPM adds a huge attack surface for no practical reason. A large enough attack surface in this case that it is almost for sure going to be broken. The user only is going to be entering the password/phrase once per boot. Things are different in the case of something like a phone. In that case you are pretty much forced to use some low entropy key that could otherwise be brute forced. Then a secure hardware device makes sense, particularly if the phone does not use the device for everything but the kitchen sink as in this case.

mjg59 9y ago
There's a huge practical benefit - the user gains disk encryption without having to remember a secure passphrase. That's a big deal.
- marcoperaza 9y ago
  Exactly and to elaborate, it means that the only secret a user needs to remember is a short PIN for OS-level authentication. The TPM's protection against modified boot and OS components make a brute force very difficult. Further, Windows will actually feed that PIN to the TPM for purposes of OS-level authentication, which leverages the TPM's enforcement of rate limits and lockouts in addition to OS-level implementations of those protections. A nice improvement would be to use a PIN entered at boot for purposes of drive decryption and then automatically pass it through to the OS-level login.
- cm2187 9y ago
  And for a server it enables to reboot autonomously while protecting you from someone pulling a hard drive from the array (think server colocation).
brians 9y ago
It sounds like your threat model doesn’t interactive hardware adversaries. Mine does, so worry about how they might capture my long pass phrase is a big concern. Well, to whom do I tell my long passphrase? Right: my computer. Every morning. Is it running the same software as last night, no keyloggers, etc? That’s what the TPM is for.

mjg59 9y ago

There's a huge practical benefit - the user gains disk encryption without having to remember a secure passphrase. That's a big deal.

marcoperaza 9y ago
Exactly and to elaborate, it means that the only secret a user needs to remember is a short PIN for OS-level authentication. The TPM's protection against modified boot and OS components make a brute force very difficult. Further, Windows will actually feed that PIN to the TPM for purposes of OS-level authentication, which leverages the TPM's enforcement of rate limits and lockouts in addition to OS-level implementations of those protections. A nice improvement would be to use a PIN entered at boot for purposes of drive decryption and then automatically pass it through to the OS-level login.
cm2187 9y ago
And for a server it enables to reboot autonomously while protecting you from someone pulling a hard drive from the array (think server colocation).

brians 9y ago

It sounds like your threat model doesn’t interactive hardware adversaries. Mine does, so worry about how they might capture my long pass phrase is a big concern. Well, to whom do I tell my long passphrase? Right: my computer. Every morning. Is it running the same software as last night, no keyloggers, etc? That’s what the TPM is for.