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Comment by captainmuon | Hacker News Reader

Interesting project, I'm sure this is useful for people at risk.

Somewhat related, I'm wondering about the physical security of computers. There is an attack where they open your PC, take out the ram, and freeze it immediately so the bits don't decay and they can extract your encryption keys.

All BIOSes have an option for cassis intrusion detection, but I've never seen a case that has the necessary cable. Has anybody here set up a chassis intrusion kill switch that erases the RAM/shuts down the PC etc. if the case is opened improperly? Can you buy anything like this on the market?

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Memory encryption technologies such as AMD's Secure Encrypted Memory (SME). Would be your best bet to combat this, along with other anti-evil maid protections.

https://en.wikichip.org/wiki/x86/sme#Overview https://www.qubes-os.org/doc/anti-evil-maid/

There are also things like TRESOR [1] which keep all encryption keys inside the CPU. I'm not sure what the current state of the art is.

There are so many possible evil maid attacks that I think it would be useful to add a pysical layer, just in case.

[1] https://en.wikipedia.org/wiki/TRESOR

TRESOR is a great project but pretty seperate to SME imo. TESOR implements SME but its implemented effectively in software, making it less secure and a lot slower. The great thing about SME on AMD CPUs is that I believe (at least on the newer Zen cores) it effectively can run at the speed of the memory, so you have no performance loss.

I think SEV is newer form of this.

Secure Encrypted Virtualisation uses SEM, but it is not a newer version of it. SEV allows someone to run encrypted VMs that not even the host can read the memory, by leveraging per VMs keys in the AMD PSP that encrypt the VMs pages using SEM.

It would be interesting to leverage SEM to run a version of qubes where not only are the VMs isolated by the Xen hypervisor but are also separately encrypted using the PSP.

Here's details of this attack for people who want more details https://citp.princeton.edu/our-work/memory/

If memory serves correctly they achieved the best results by using a can of compressed air to freeze the ram in place before removal.

//Small edit to wording

Many of the measures that provide effective physical security also make a device really unsuited for personal usage. Look at HSMs for an example of this. And even they rely on being stored in a physically secure room and protected from theft.

It's a matter of being more determined than your attacker. Imagine a device that will irretrievably brick itself if tilted more than a certain angle, if left unpowered for more than a certain time, etc. and that has to be under constant guard. This seems almost incompatible with any kind of personal use. And some measures may only work in one instance, with the attacker planning for them the second time they have an operation.

Many attackers also don't have the same restrictions the police has. In the Ulbricht case the police may have been forced to use a device that copies the data with no human intervention just to preserve the chain of evidence and not have suspicions that the agent operating the laptop altered it while installing additional software. An attacker operating in the grey/dark area might just immobilize the user, snip the wrist cable, and then retrieve the necessary data either directly at the console or by siphoning it via the network. Or the police may just start video recording in great detail every step from the moment an agent touched the laptop until the data was exfiltrated to remove suspicions of tampering.

But such a tool would be of great effect against an undetermined, unsophisticated attacker committing a crime of opportunity.

Personal computers have an advantage here: it is acceptable for them not to work when they are not directly used by someone. It means they can be stored in safes when not used and have all the encryption keys securely erased when not used. For example, a screen locker could stop all the processes and erase all the keys from registers and memory assuming both disk and memory encryption. And the locker itself could be triggered by some proximity sensor, RFID, camera, whatever, not just input inactivity timeout.

Storing your personal computer in a safe when not using it is probably the very definition of "almost incompatible with any kind of personal use". And at this point you just move the weak link from the device to the safe's lock. HSM-like physical security is good for making the device tamper proof and ensuring than no data can be retrieved under any circumstances other than the one accepted "regular use" way.

Putting a regular device in a safe leaves it exposed to someone unlocking the safe and compromising the device by implanting a keylogger inside or even by putting a replacement identical device there and waiting for the user to type the boot password.

As for methods of emergency clearing sensitive data from memory while in operation, whatever method is employed will work once. The next time the attacker is ready for that particular method. For example the police might just have to completely immobilize the suspect (and their hands) and keep the laptop in the vicinity while the "dead man's switch" is bypassed.

> And even they rely on being stored in a physically secure room and protected from theft.

Not exactly. You don't want someone sneaking in and misappropriating the HSM to authorize something bad. And if you set the system up for unattended recovery from a power failure, then in all likelihood someone walking off with the server the HSM is in can use those keys indefinitely. But there are options.

Some HSMs have self-destruct mechanisms that attempt to prevent physical access to the private key (ie by lapping the chip). Some vendors (nCipher, IIRC) have a smart card (a second HSM) that is required to authorize certain activities, like signing, or key recovery. In fact they had a byzantine generals solution that either had the key or a password for the key split between n cards. In the latter case you needed one of the original HSMs in order to clone the key, so a movie plot where you kidnap the entire team at a conference doesn't work. During initial setup the cert would be generated on the first HSM and copied to the others, having never seen daylight.

That system was quite difficult to explain to users, and I had to document it just so I wouldn't get confused and trigger a reset of the evaluation hardware (at which point all of our test artifacts have to be rebuilt).

It might be more complicated to start WWIII than to protect a signing certificate, but only just.

> Not exactly. You don't want someone sneaking in and misappropriating the HSM to authorize something bad.

I think we're talking about exactly the same thing :). That's what I meant by "even they rely on being stored in a physically secure room and protected from theft". Despite all the hardening that is applied to the device, it must always be kept secure and supervised. As an example, this is what Safenet considers the intended installation environment should be [0].

This can't be effectively applied to a personal computer.

[0] http://cloudhsm-safenet-docs-5.3.s3-website-us-east-1.amazon...

As I was trying to say, there are ways to make that less of an issue by moving other factors off-site. You can configure (some) HSM cards not to be available on boot, requiring a human to come in and reactivate them with a password or a fob that they bring with them, and leaves with them.

Then your biggest problem is people thinking that stealing the cards will get them anything. Which, they're not entirely wrong, because those things are damned expensive. So you need a 'kinda' secure facility.

Again, the issue is that any hardware that will start up for you without any action on your part will likely start up for anybody else, too. Your laziness will probably win out...

Does anyone have pointers as to whether this is even possible with DDR4 on modern machines?

I think the real question is has it ever been used in the wild on any DDR?

"In recent years, however, it has become increasingly challenging to execute cold boot attacks or perform physical memory forensics due to the introduction of DRAM memory scramblers. Modern processors with DDR3 and DDR4 DRAM scramble data by XOR’ing it with a pseudorandom number before writing it to DRAM [5], [6]. These scramblers were initially introduced to mitigate the effects excessive current fluctuations on bus lines by ensuring bits on the memory bus transition nearly 50% of the time"

DDR4 is also yes in the lab -

https://web.eecs.umich.edu/~misiker/resources/HPCA17-coldboo...

I have a Lenovo M93P Tiny which came with a chassis intrusion switch installed. It seems you can have it block startup/require a password when the case is opened and notify some central admin. I don’t know what happens if you open the case while it’s running, though.

I’m not sure if it’s something they offer on current models, or to individuals at all (I bought it used from a corporate IT asset liquidator so it was likely originally purchased as part of a bulk deal). Regardless it makes a great little Linux box!

Work at a big bank , we won’t procure laptops without this and yes we will know when you have opened it and you won’t be able to boot it , I think something happens with bitlocker also but not sure.

Could you give examples of laptops with this feature? I never knew chassis intrusion sensors were a thing on laptops.

Also, does it still work if you open the machine with the power disconnected and battery removed?

I'm pretty sure most thinkpads have case intrustion detection. It's callled "Bottom Cover Tamper Access Detection" in BIOS.

That feature is fairly common but practically quite useless and easy to circumvent if you can find the model information. Even with PCI-DSS enclosure compliance you can get in if you can take power tools to it. The assumption is power tools would be too obvious to use in a typical installation.

Back in the BBS days, there were textfile describing how to wire your beige box to either turn on strong magnets or ignite termite if a case was detected.

... I don’t know of anyone actually implementing this though :)

I would imagine that's thermite and not termite ;)

If the latter, the server would probably be okay, and it would take a very long time for the termites to damage the surrounding room enough to be a security deterrent.

Nah, it's termite. You're trying to destroy your logs, right?

Ha! Very nice :)

Probably just a debugging technique.

Well, it certainly complicates debugging.

or a bugging technique?

Sorry that was a typo. Haha!

It's funny when I think back, I was a teen in the 90s and did plenty of questionable stuff online and w/ local BBS scene (Kevin Mitnick was busted in Raleigh and many rumors existed about his presence in the BBS scene, obviously fantasy though!).

Nobody I know who got arrested ever managed to destroy anything. When I think about it, we all assumed the cops would storm in when we were in the act of doing something bad, probably like in the movies lol, when in practice, they tend to pick you up when you are really off guard, duh.

Very few people had automatic protections because like, our parents would probably get mad if we burned down the house :)

When it came to me, the FBI did knock on my front door, and I managed to dd if=/dev/random of=/dev/hda

I lost my entire BBS, all the custom code and ANSI I had for it, among other ancient treasures that I'd probably still have with my napster mp3s :)

Of course they didn't come for me, there had been a flasher in the neighborhood on halloween...

Hehe, yeah :)

When I was a teen, I somehow got a modem number at NASA, and I stupidly gave it to a friend. He tried to brute force it, but he got door knocked. He quickly formatted his disks, but it wasn’t even the cops haha!

This is how you earn tampering with evidence charges, up to 20 years felony.

Well, keep this in mind: I knew quite a few people who got interviewed with, and arrested by authorities. Everyone under the age of 18 in the 90s got a slap on the wrist because they hadn't got too good at punishing those kinds of crimes. I think the worst I saw was $1200 paid over 12 months to AT&T.

After 18, you're done, even if they can't think of a good charge, they'll make them up, which is exactly what they did back then, cross state commerce was a blanket thing to grab folks.

I stopped doing anything questionable well before I turned 18.

Eh, it's worth it, depending on what you're doing. I'd much rather get in trouble for a hard drive full of zeroes, than them knowing what was on it beforehand.

Today, you should encrypt everything, and cut power before physical access is obtained. Will that count as "tampering"? I was just turning off my computer. No, I do not remember the key.

Looking back, federal authorities really only came when they had the evidence they needed already, and local authorities were way too far behind to know what was going on (in the 90s).

In practice, the only real protection we had (those of us in my social group) was that we were minors, and lucky that laws hadn't caught up yet.

Surely it has to be actual evidence before you "tamper" with it.

If I delete a file on my computer today that would be potentially "evidence" if seized, and the police come knocking tomorrow, I haven't committed a crime by using my personal computer in the past.

I do not suggest that you test this theory. Your optimism seems wholly unwarranted here, knowing what we know about the federal prosecutors.

The FBI was investigating a flasher?

I could be remembering incorrectly, but it may have been reoccurring or not even really the FBI, but state police or something and my parents said it was the FBI.

I only saw people in suits with a black car outside knocking on the door, also this was like 30 years ago so don't twist my arm :)

This was a plot device used in the TV series Mr. Robot Season 2, Episode 3, about 27 minutes in.

Some ideas have been tested, there was an entertaining talk a few years back at DefCon: https://www.youtube.com/watch?v=-bpX8YvNg6Y

DEF CON 23 - Zoz - And That's How I Lost My Other Eye...Explorations in Data Destruction https://www.youtube.com/watch?v=-bpX8YvNg6Y

Hacking with Ramzy.. 14 years old now!

https://www.youtube.com/watch?v=-hNQ280Zkk4

I think in most cases the thermite trap would probably get you into more trouble for ATF violations and not even help by adding destruction of evidence and whatever they imagined was on the drive unless you had some authority like security clearence and classified documents or some sort of legal pretext to justify uses of such flammable boobytraps.

I doubt there is a need to open the case for a sophisticated attacker. If there is even the slightest opening for air you can run camera optics and freeze spray tubes to RAM I would imagine.

This is why security-sensitive devices are often encapsulated and potted in epoxy or similar.

Chenbro makes cases with intrusion detection, bought one nearly 20 years ago and they still make similar ones: http://www.chenbro.com/en-global/products/TowerServerChassis...

Agreed; but this USBKill is a good protection for ordinary city police, or even a grab-and-run crime at a coffeeshop (with a usb key attached to your wrist with a cord).

Touch Bar MBP's are protected against this right?

> Interesting project, I'm sure this is useful for people at risk.

Could you expound on what this means? In the USA/UK, people most "at risk" of police kicking down the door seizing their laptops/computers while they are still running are child pornographers.

Perhaps this can be used "for good" under oppressive regimes (i.e. if you are a dissenting journalist) but then I think you won't get a fair trial anyway and having a kill switch just means more prison.

I know a shocking amount of innocent people who have been target of surveilance and criminal investigations or who even had their homes raided - in western european countries. Thankfully the courts are still working as they should, and all but one were fully acquitted.

It can happen if you are a political activist in any fashion. Nothing violent, just speaking out for rent control and against gentrification can get you in trouble. Or hanging around with the wrong people.

When it happens, you want to leave them as little rope as possible to hang you with. As I said, the courts still are honest and they won't make up evidence, but they will take everything they can find to make a case - and to learn about your structures and networks while they are at it.

You are right, that in real oppressive regimes all bets are off. If they want to get you, they won't stop at their own laws. But even then, these techniques are useful against industrial espionage. If you are doing business in certain countries, the "evil maid" is quite real...

This is a somewhat pessimistic outlook on humanity, first off I would say that those who are most commonly at risk are those with trade secrets. Patented tech and investment intel for example.

As for the dissenters, I’m sure they would appreciate their co-conspirators remain secret.

> This is a somewhat pessimistic outlook on humanity, first off I would say that those who are most commonly at risk are those with trade secrets. Patented tech and investment intel for example.

Can you provide any evidence at all of police or "thugs" (or anyone, really) kicking down doors to get at trade secrets being a common problem? Because there are countless news articles of police raids seizing computers to stop child porn[0].

I speculate any tool billed as "anti-forensic" will be used for immoral purposes more commonly than moral purposes.

[0] https://en.wikipedia.org/wiki/Jared_Fogle#Child_pornography_...

It is an absolute certainty that any tool to improve privacy and security is going to be used by malicious actors.

That does not mean it should be banned. Knives are used for many things from cutting food and opening boxes to killing people. Nitrate based fertilizers can be used for vastly improving crop yields but can also be used for bombs. Encryption can be used to protect your sensitive personal data from criminals and prying eyes, but can also be used by the criminals themselves to hide their activities.

No state (even if it was the most ethically illuminated utopia) has the power to protect every person in every place at every time. Banning defensive tools is asinine as rarely does it mean that a criminal won't use them against you.

That is a dangerously naive viewpoint - trusting that the only instances are the ones they proudly brag about? When they have been caught not even allocating all of the funds for Child Pornography prevention they have been allocated while using "the children" as an excuse to undermine cryptography?

It is doubly foolish to believe that the police are the only users of forensic software when there is credit card theft and multmillion dollar ransomware rings out there. Robbing a bank by force or by heist is foregone jail but snatching a laptop from a banker? Far more petty in risk and disguised as mere property theft as opposed to the data theft.

The threat model in corporate espionage is absolutely one of theft of property. It’s a lot easier to steal somebody’s laptop than to hack it.

Suspected child pornographers. There was some concern that the door kicking had gone too far on too little evidence once it reached Cliff Richard.

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