Comment by noinsight
6 hours ago
If you’re at all serious about security and not user convenience, you deploy BitLocker with a PIN instead of TPM only. And then a whole class of vulnerabilities goes away.
6 hours ago
If you’re at all serious about security and not user convenience, you deploy BitLocker with a PIN instead of TPM only. And then a whole class of vulnerabilities goes away.
It's probably all security theater. There's only so much trust you can put into some shitty vendor's TPM implementation
"Disk must be in expected hardware environment" versus "Same environment plus PIN" makes a huge difference if a thief simply steals a whole computer.
If you are at all serious about security you don't consider Windows.
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
And then depending on how "serious" you are you also don't consider Linux.
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.
People just plain suck at opsec. Like Che Guevara might have had a longer career as a revolutionary if he'd used his one time pads only once.
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.
Just a PIN? For most people that's a 4-digit number, which has a worst-case scenario of 10,000 attempts and a median of only a few hundred. Why not use a full 8-digit password?
Because the TPM effectively rate limits brute forcing of the key.
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.
In that case, the median would still be just over a month, if the PINs were entered in order of how commonly they are used. Even the worst case of two years is still soon enough for a lot of data still be useful.
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.
4 replies →
> the TPM effectively rate limits
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.
No one uses a 4-digit pin for BitLocker. No one who knows what they are doing, anyway.
My employer requires at least an 18-digit PIN, and not just numbers, either.
If you're really serious, you use a strong password, not a PIN.