3 ms·

For those who use BitLocker: although it is set up to use numeric-only PINs by default, you can configure this to allow any character - which would presumably i

For those who use BitLocker: although it is set up to use numeric-only PINs by default, you can configure this to allow any character - which would presumably increase the search space of brute force attacks against the PIN. The relevant Group Policy setting is "Allow enhanced PINs for startup", and can be found in Windows Components → BitLocker Drive Encryption → Operating System Drives.

MichaelGG 11y ago
The big question is: is your PIN used only for TPM access? Or is the PIN itself combined after unlocking the TPM? How it should work is that one hash of your PIN is used to unlock the TPM. Then another hash of the PIN is used to mix into the key the TPM provides. That way directly compromising the TPM doesn't provide full access. This is probably strictly obsolete by using a long PIN. But it feels nice to have a TPM, as it's one more piece the attacker needs. If they steal the disk or fuckup the TPM, then the data's gone, even if you reveal your PIN. (ATM, I use Bitlocker, then encrypt my VMs with EFS keyed off a certificate stored on a smartcard. Then I Bitlocker the VM drive itself. It's silly, but that way I get a range of hardware plus brain-stored password. [I don't need it any more, it's just a leftover setup from my BTC experiments.] I also put tamper proof seals all over my laptop, but it requires active work to check them and note the serial number on each one.)
- geographomics 11y ago
  I wondered that too - apparently in Vista the PIN was only used to authenticate to the TPM and retrieve the volume master key (which in turn protects the key used to actually encrypt the drive). More pleasingly however, in Windows 7 and onwards it is used to encrypt the volume master key as well, in pretty much the way you describe. Microsoft's submissions for FIPS validation have some good detail on this - Windows 7 [see section 7]: http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/140sp1332.pdf http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/1..., others: https://www.google.com/search?q=site:csrc.nist.gov+inurl:140sp+microsoft+bitlocker https://www.google.com/search?q=site:csrc.nist.gov+inurl:140...

MichaelGG 11y ago

The big question is: is your PIN used only for TPM access? Or is the PIN itself combined after unlocking the TPM? How it should work is that one hash of your PIN is used to unlock the TPM. Then another hash of the PIN is used to mix into the key the TPM provides. That way directly compromising the TPM doesn't provide full access. This is probably strictly obsolete by using a long PIN. But it feels nice to have a TPM, as it's one more piece the attacker needs. If they steal the disk or fuckup the TPM, then the data's gone, even if you reveal your PIN. (ATM, I use Bitlocker, then encrypt my VMs with EFS keyed off a certificate stored on a smartcard. Then I Bitlocker the VM drive itself. It's silly, but that way I get a range of hardware plus brain-stored password. [I don't need it any more, it's just a leftover setup from my BTC experiments.] I also put tamper proof seals all over my laptop, but it requires active work to check them and note the serial number on each one.)

geographomics 11y ago
I wondered that too - apparently in Vista the PIN was only used to authenticate to the TPM and retrieve the volume master key (which in turn protects the key used to actually encrypt the drive). More pleasingly however, in Windows 7 and onwards it is used to encrypt the volume master key as well, in pretty much the way you describe. Microsoft's submissions for FIPS validation have some good detail on this - Windows 7 [see section 7]: http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/140sp1332.pdf http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/1..., others: https://www.google.com/search?q=site:csrc.nist.gov+inurl:140sp+microsoft+bitlocker https://www.google.com/search?q=site:csrc.nist.gov+inurl:140...