But I would never trust it a second, being proprietary and known for issues. You likely know that, but for the benefit of others:
38C3 - Windows BitLocker: Screwed without a Screwdriver https://media.ccc.de/v/38c3-windows-bitlocker-screwed-withou... https://www.youtube.com/watch?v=5eNtT2p12cM
BitLocker with a password (the equivalent of the LUKS configuration in question) does not share these issues.
I can understand the default being TPM-only + online key backup, huge amounts of the population forget their login passwords (which can be involuntary, e.g. head injury) and huge amounts of them still want some backup way to access their data rather than losing it forever.
But for anyone who cares just a little more, or would prefer to lose data in those situations, it's such an abnormal and hidden path that it's clearly blocking tons of people from choosing it.
It is annoying that they hate password for system drive _so_ much; the reason is actually pretty obvious when you think about how their "happy path" AD-driven enterprise deployment with stupid password rotation requirements works (and FileVault is a nightmare in this scenario), but I wish they'd make it easier for individual power users.
Depending on how serious you are you also don't consider MacOS.
And then you kinda have a couple of things to chose from but ultimately you need to build your own security depending on your attack/threat model
But also, threat models and the best way to mitigate them aren't really a linear scale of being <unserious> to <serious>, but a complex consideration of a particular situation.
Back in the late 1980s it was clear that it would be no problem at all to hook up a hard drive to a digital phone exchange and record all the calls! I had a strict policy of "don't talk about anything illegal using electronic communication" even when it was rather banal stuff like selling weed.
The carelessness of people at Facebook documenting policies that nobody in their right mind would document boggles my mind: you might as well leave it mysterious why you didn't crack down on scam ads, for instance. When I've been involved in minor conspiracies, say when we had an HR problem with another employee, I've always made the point to meet furtively in person and avoid leaving a paper trail so that I'd never need to explain an email I wrote in front of an unfriendly audience.
https://learn.microsoft.com/en-us/windows/security/hardware-...
> For example, when BitLocker is used with a TPM + PIN configuration, the number of PIN guesses is limited over time. A TPM 2.0 in this example could be configured to allow only 32 PIN guesses immediately, and then only one more guess every two hours. This totals a maximum of about 4,415 guesses per year. If the PIN is four digits, all 9999 possible PIN combinations could be attempted in a little over two years.
Also, how is the time limit enforced? With hardware access, it would be easy to change time or increase the clock rate, as well as many other side-channel attacks that could eliminate the wait altogether.
Anyway, crystal oscillators connect to one input pin and one output pin, with an internal feedback circuit that causes the crystal to resonate. It's possible to change out the crystal for a higher frequency, or even directly drive the input pin for a much higher frequency. Semiconductor manufacturers often only characterize the limit of the feedback circuit, but not the limit of the internal clock circuitry when directly driven. Considering that the logic design supports an SPI bus running up to tens of megahertz, it's totally possible that the crystal input could be driven at a similar speed, possible a thousand times faster than a normal real-time clock oscillator.
There would be several ways to mitigate such an attack, but a quick search for TPM side-channel attacks brings up multiple much simpler vulnerabilities, so it's not likely that TPM manufacturers are putting any real effort into mitigation.
>It's possible to change out the crystal for a higher frequency
You can't access the internals of a TPM by design.
I had a friend working at trusted compute at Microsoft, and he had so many stories.
These TPM firmwares are often written by shitty companies that have no fxcking clue what they are doing.
Most TPM implementations are a clown show, companies just want to check a box on paper so they say "look! We have a TPM!" and move on.
Looking at the manufacturers of TPM ICs, it makes sense. Most of them make microcontrollers that have code-protect bits in them that are notorious for being susceptible to simple side channel attacks, but also for not being a target simply because no one cares about the object code on any random product's microcontroller.
I worked at a company that sold a microcontroller that executed from external memory, so there was no possible way to have built-in code protect bits, and some potential customers complained until we included a library to encrypt the external memory, run a small unencrypted bootloader which included the a plain-text decryption key, then run the encrypted program. That checked their box, despite doing nothing useful.
My employer requires at least an 18-digit PIN, and not just numbers, either.
While true if you don't trust the proprietary encryption you shouldn't trust the proprietary OS either. I think bitlocker backdoor or bugs should be the least of your concerns when the OS is literally known for covertly exfiltrating data to the cloud.
Bitlocker + PIN is as secure as anything.
A vulnerability can’t leak your key if the TPM doesn’t know the entire key and relies on the user to supply the missing parts of the key in the form of a PIN.
First off: I agree with your thesis, BitLocker with PIN is Just Fine, equivalent in all practical senses to most disk encryption strategies, and an enterprise standard.
I post this to reinforce what you're saying, because there are a ton of weird theories about how this works that make people think it's weaker than it is.
BitLocker with PIN works like this:
* BitLocker seals an encrypted key IK into the TPM using a policy on the TPM which requires the SHA-256 of the PIN to be sent to the TPM to unlock the record (and has anti-hammering at the TPM level).
* Encryption using another key called the SK. Once the OS acquires the e(IK) from the TPM, it needs to derive SK to decrypt the IK. The SK is generated by applying a salt and 0x100000 rounds SHA256 to the PIN.
* The IK can then decrypt the VMK, which can decrypt the FVEK which is the actual data encryption key used on the on-disk data.
Fully offline (no TPM access) decryption is hopeless; the IK is random and not attached to the PIN at all.
Fully online decryption relies on TPM anti-hammering; if you can manage to hammer the TPM and find a PIN where h(PIN) matches, you can then use the PIN to generate both h(PIN) (unseal TPM) and reverse e(IK).
Partially offline decryption (imagining TPM content is somehow dumped, for example by bus sniff while a user uses their PIN) relies on bruteforcing the key for e(IK), which is possible but difficult (IMO Microsoft should ratchet this up or use a more expensive algorithm than SHA-256 in order to deal with modern hardware capabilities, but they have issues like FIPS to deal with that make new algorithm selection difficult).
10 points deducted. Try again.
last famous words? :D
Explain how an exploit can decrypt the drive without the portion of the key that the user must enter. The computer doesn’t know the entire key, and can’t decrypt the drive without it, or the recovery key. This is why BitLocker with PIN hasn’t been defeated yet. I don’t understand how it could ever be defeated without entering the PIN.