Detecting unauthorized physical access with beans, lentils and colored rice (2021) | Hacker News Reader

Detecting unauthorized physical access with beans, lentils and colored rice (2021)

dys2p.com

642 pointslayer8162 comments

Lovely work. Here's a similar project where I showed that randomly-placed multicolored candy particles (nonpareils) can be used to confirm the authenticity of pharmaceuticals: https://www.nature.com/articles/s41598-022-11234-4

As a giant identifier nerd, this is incredibly cool. Any insights/thoughts on tamper resistance/non-duplication? I realize that this is a bit outside the original use case/threat model, but would it be possible to ensure that any physical injury to the coating would ensure that the code would no longer match? Seems like a challenge because you want robust matching but not robust enough to allow someone to substitute or reproduce the exact pattern.

I'm fairly certain that this cannot defend against a determined adversary buying up a bunch of pills, reading out the ids, and then reproducing the patterns (which would already be in the database) or similar enough patterns via a non-random process. Only useful for substitution attacks where someone trusts a pill because it is in a database without realizing that its contents could have been substituted for e.g. poison.

This may be obvious, but it also seems critical for any database that might use these to have expiration dates, otherwise expired pills could be bought in bulk and resold or have their codes reused.

> As a giant identifier nerd,

Not something you hear often. =D

Very cool work! Speckles could be added to the pill itself to eliminate the possibility of shipping damage, though it was good to see you tested that.

I know explosives are often laced with statistical chemical properties that identify them. I was wondering if that could be done to limit ammunition purchases as a way to get around gun control.

Thank you for sharing that, I really enjoyed reading your work, it looked like a fun project.

In addition to authentication, I imagine they could also be used to double-check expiration dates or as a last-ditch effort to notify consumers in the event of a recall. Being able to precisely identify exactly which factory and batch any given pill or other edible item came from could be very useful in some cases.

My grand mother used to identify pills to take with the color.

Something like Take RED ones in afternoon, Take the capsule in evening. Would be a pain for her if each one has a different color.

It's common to have compartments that organize your pill schedule, usually with 14 labeled cells - morning and evening for each day of the week.

Set it up once a week and then just take the pills in the appropriate cell when the time is right. This also solves the problem of "did I already take my pills for today?".

I saw those compartment sheets recently. They aren;t really widely used in my country.

It's a good memory aid, since most (all?) memory is associative in nature. Just coming UP with that system kept the neurons active some, if even a little.

But pills already don’t have unique colours.

There are other attributes as well - the combination of colour, size, shape and surface features might be unique in many people's mixes.

They aren't different colors. They have are a standard color with a standard sprinkle, but the details of the sprinkle are unique, like a (real) fingerprint.

That's really a cool study! Do you think this will be adopted at some point? are there currently any efforts to solve this problem?

I was told the blockchain will solve this ;-)

If I were actually going to use a method like this in real life especially for international shipping etc, I’d probably avoid using rice or beans or other plant material to avoid unnecessary inspections at customs. I feel like this would definitely get stopped and inspected, where a block of multicoloured plastic or resin might not be.

Maybe use injection mold resin pellets instead. They’re not as convenient as rice or lentils, but there are a lot of color choices.

Rice and beans are considered hazardous cargo because, when exposed to moisture, they expand significantly and can rupture their packaging.

I'd think that a block of resin would be equally suspicious, warranting an inspection immediately, but IANACBPO.

Otherwise, a block of (say) white icing sugar, encapsulated in a block of (opaque) resin, would pass a machine inspection and icing sugar-sniffing dogs at the border... and a lot of icing sugar would enter the country in a resin mold.

A block of multicoloured plastic or resin with electronics in it (visible in the airpot xrays) IMHO is quite sure to raise all kinds of red flags.

I guess the point is detecting the inspection, not avoiding it.

There are customs regulations against importing foodstuffs in many areas. For international travel or shipping, this might prove problematic on those grounds.

Rice, for example, is not allowed or might require specific permission to import into Australia. Coffee, noodles, pasta, pepper, and wheat might be restricted.

https://www.abf.gov.au/entering-and-leaving-australia/can-yo...

If you are just getting package disturbed 100% of the time by TSA, that makes it useless to detect whether or not somebody else also tampers with it.

My wife (shameless plug: https://messyplaykits.com) recommends liquid water colors instead of food coloring (cheaper and better color).

Colorations brand from discount school supply or amazon works well for her and she makes a lot of colorful rice!

Thanks for plugging. I wish I had known about this during the various lockdowns of the past 2 years. It never occurred to me to look. (Aside ... reflective moment on the possible value of ads and failure of ad tech)

It's great to see someone packaging what look like Reggio style provocations. I hope she is as successful (or more) as Love Every has been with aesthetic Montessori objects.

She worked at the UC Davis lab school which is Reggio inspired, so right on point.

Thanks!

Interesting that you say 'inspired'.

I've noticed that ECE can be Montessori or Waldorf but never Reggio -- instead it's 'Reggio inspired'. I thought this was a local quirk of how programs describe of themselves but perhaps it's more widespread.

This is a cool site. Definitely bringing back memories of playing with arts & crafts kits in kindergarten lol

If I may ask, how successful is this? I feel like this is in a similar space to kiwico (not exactly, but it's similar enough I imagine both that they could quickly take over, and the average person is probably more aware of kiwico even if it's not the same offering(s)). I have had an idea for awhile that's also somewhat similar to kiwico's model, although different enough I'm still tempted to pursue it, and this is the first comparable company other than some popular YouTube channels that I've found.

Has your wife had any discussion with kiwico? Is kiwico a threat to success? Are there noticeable advantages/disadvantages to subscription vs á la carte sales?

It’s a small home based business, but that’s allowed her to keep control and grow sustainably-I’m not quitting my tech job any time soon, but we are also expecting our first baby in October so might look into more effort on advertising once we know how much growth we can handle.

Definitely very similar to kiwico, no direct conversations, not that worried as there is a fair amount of overlap as well as differences.

She’s done lots of approaches over the years (eg selling at festivals pre-Covid) and life is a lot easier now that the focus is mainly subscriptions.

Phone number is on the site and she says she’d be happy to chat if you want to give a call.

I was expecting more stealthy techniques, like the old sticking a hair and tape on a door or carbon shoe prints under the carpet type tricks. I was imagining people spraying invisible coatings on USB sockets or something.

The problem with doing something as elaborate as wrapping stuff in vacuum packed beans is that it draws attention and provides an adversary plausible deniability due to customs inspections etc, "Oh sorry the DEA had to inspect your package but it's fine, here's your beans too".

Is that really a problem? I think you’ve described a valuable signal, and you may have a different threat model in your mind.

If my use case for this device is so sensitive that I’m taking these steps to avoid it being intercepted, any evidence of tampering, even slight, means the device is compromised, /full stop/.

In your scenario when the government hands me three bags of lentils & my device I thank them, walk to the nearest dumpster, and pitch the whole lot in because I have to assume it’s been bugged.

True, my point is only that it's far from free and therefore has limited purpose... You gain highly reliable interception signalling at the cost of significantly increasing the probability of interception.

As you suggest, if your use case is so sensitive or critical that you can afford to send 10 laptops and only use the ones that arrive in tact then fair enough - however for the more common scenario of just being a privacy conscious individual who would like some degree of ability to determine tampering in transit - this is a non-starter.

It's not unthinkable that a method exists with as much resilience without attracting unwanted attention.

Good point, but if my package contained illegal material, I'd know I'm being played. Of course, they'd just arrest me instead in that case, but maybe that's preferable?

When flying I often lock my suitcase with a zip (the plastic strip you buckle up on its own, works one way). I got red and green zips because they are less common.

I do this to detect obvious attempts at opening the suitcase (to have a look what is inside, or to plant nuclear weapons for me to transport them).

When the suitcase is on the reception belt, I inspect the zips and if they are broken (or missing) i immediately go to the police/customs agents for them to inspect my suitcase because I see it was tempered with.

It happened twice that the zips were missing. There was no problem for the agents to inspect my luggage. Nothing was found or missing, the zips were probably broken during transport (or someone had a look inside but did not find anything interesting.

> with a zip (the plastic strip you buckle up on its own, works one way)

Just in case you didn't know, unless you buy ones that are specifically hard to open (like if you instead use ones from a random hardware store), they are trivial to open without breaking it by lifting the flap inside the lock-mechanism with something thin and sharp, roll it back out and inserting it again once you've done your deed.

I used the ones that are specifically hard to open (you basically force a blade into a part and if you want to remove it it is destructive).

It will not protect le against everything, and this is the reason i do not go for anything fancy. I just hope that the ones who would like to put something in would be deterred by the zips.

Anything that breaks visibly (a seal for instance) would do, but this leaves traces on the suitcase.

Glue, most likely super glue (cyanoacrylate) would likely counter that vulnerability. There are also tamper evident zip ties.

This is a wise thing to do. I knew a guy who frequently travelled to the USA who one day got home and discovered something in his suitcase that neither he nor his partner had put in there.

The question "did you pack your bag?" that customs officers ask is used to infer guilt. Once you answer yes to this question you are criminally liable for whatever is in the suitcase. In Australia a number of baggage handlers have been convicted of trafficking drugs. Unsuspecting tourists have also been convicted of drug trafficking and sentenced to 10+ years in prison

A company makes security seals for this very purpose and markets them under the name "TamperTell". They have a serial number on them and a matching receipt tab that you remove before flight then check against on arrival.

> A company makes security seals for this very purpose and markets them under the name "TamperTell". They have a serial number on them and a matching receipt tab that you remove before flight then check against on arrival.

I wouldn't put too much trust into the marketing of products like this. Time and time again they fail to protect against the most basic of "lockpicking", and unless I've seen multiple skilled people failing at unlocking the "TamperTell", I'd put it in the same bucket as the rest.

> DEF CON 18 (2010) held the first ever "Tamper Evident" contest, where contestants were given a box sealed with a variety of tamper evident devices, many of which purport to be "tamper proof." All of these devices were defeated, even by those with little experience and a limited toolkit. Like the computer world, many of these devices are overmarketed

https://www.youtube.com/watch?v=W07ZpEv9Sog

I get your point but since most locks are pickable does that mean that I shouldn't bother locking my doors?

The threat vector I am defending against is one baggage handler in one airport putting drugs in my bag and another baggage handler at the destination airport retrieving them.

Why would they go to the hassle of having to fiddle around with a bag with a seal on it leaving prints in the process? If they want to use my bag to smuggle drugs they will most likely just rip the tags off it. If I kick up a fuss at the destination airport they will find nothing out of the ordinary in the bag and assume that customs inspected it at departure or the seal somehow broke off in transit.

Ha, nice. I was a silent participant of that contest that year. My buddies team was able to acquire a second tamper kit to practice on, I learned a lot about seals that weekend and I still apply that knowledge to this day.

Any seal that uses an adhesive is often easily removed with acetone. Seals that use multiple materials like plastic and metal, well you can dissolve the metal component and replace it if you have multiple blanks of the seal. If the plastic part is the part that is serialized then bobs your uncle.

I moved on to using security paper to make high security envelopes. There are a ton of different features you can combine to make a unique security paper. Then mechanically sealing it with security wire and a lead seal. If an evil maid needs inside they would need to duplicate the security paper's features.

This place sells a sampler pack of high security papers for cheap: http://www.secureguardpapers.com/assortment-w.html

If you want to go off the rails and raise legal questions for the government though, do this. Go to the treasury and buy sheets of uncut US currency to make your envelopes out of - remember all bills are uniquely serialized. If you are a true high roller buy uncut $100 bills, they probably have extra security features. Assuming your theoretical evil maid is a US government employee, it raises an interesting question: are NSA/US government employees allowed to forge/duplicate US currency in the pursuit of protecting national security?

If you want to see other interesting application of anti-tampering features, go check out your passport and all your visa stamps in it. The low hanging fruit is UV, but don't forget that there are two common bands of UV, shortwave is where it's at. Lots of fluorescing going on. But don't forget IR transparent inks there (or IRT). Also don't forget that fluorescence can happen in wavelengths outside the human visible spectrum. If you shine an IR laser pointer at stuff there are inks that can fluoresce from IR back into the visible spectrum. There's a ton of other things too, but your passport has a cornucopia of interesting tamper evident features.

And don't get me started on microwires. If conspiracy folks had any idea about these their heads would explode. https://security-paper.tagit-eas.ch

> are NSA/US government employees allowed to forge/duplicate US currency in the pursuit of protecting national security?

We already know plenty of things they are not “allowed” to do, but happen anyway. If they’re already invested to the level of effort it takes to duplicate security seals, I think they can call off the Secret Service from investigating a little counterfeiting.

Certainly, but imagine the reams of red tape you'll be making your agent team wade through. The FBI has a lot of resources but I suspect they are not setup to counterfeit US currency. Sooo many meetings and approvals, Judicial oversight, just to get a special run of bills from the Treasury Department. Would they be required to destroy the original evidence since they are duplicating US currency? The years of the missed soccer games and birthdays of their loved ones just to take a peek at some pepe memes that have no meaning.

Don't forget to put some sealed US currency envelopes in your suitcases while flying kiddos, the TSA needs to have fun too.

>Assuming your theoretical evil maid is a US government employee, it raises an interesting question: are NSA/US government employees allowed to forge/duplicate US currency in the pursuit of protecting national security?

Why would they need to counterfeit the notes? Is there something stopping the NSA from calling up the treasury and asking for uncut sheets with specific serial numbers?

Would they even be breaking the law if they decided to go it along and reverse engineer the printing process? While the Treasury is granted the right to print physical money[0] it does not exclude anyone else from physically printing money as well. Further counterfeiting/forging currency[1] needs to have the intent to defraud.

I get your point though. I guess it would operate similarly to the operations of undercover police who have to break laws as part of their work. I suspect a lot of oversight would be needed from the upper levels of the organisation so as not to fall foul of the Justice Department.

[0] - https://www.law.cornell.edu/uscode/text/31/5114

[1] - https://www.law.cornell.edu/uscode/text/18/471

That's a cute idea, but I wouldn't be surprised if counterfeiting a bill with a matching serial after destroying the original would be given a pass.

Destroying evidence you say?

I remember reading an article a long time ago about a passenger finding a (mock)weapon in his luggage. Turns out it was put in there by a government organization to test the process through security, except that they forgot to take it out again. I cannot find the link unfortunately.

This sounds plausible.

Judging by the size and description of the object it was not this though.

A while ago there was a big court case in Bali in which an Australian who was travelling there was accused of importing drugs from Australia. As part of their defence they claimed that the drugs found in the luggage was not theirs and that the most likely explanation was that it was evidence of some type of interstate drug smuggling operation. During this time a high ranking member of the Australian Federal Police came forward and said that it was well known within the AFP that criminals were using unsuspecting travelers luggage to smuggle drugs. At the same time people started coming forth claiming that they had returned home from travelling overseas and found drugs in their luggage. Scared and not knowing what to do they flushed it down the toilet.

> Once you answer yes to this question you are criminally liable for whatever is in the suitcase.

That's not how criminal law works in most places: "Mens rea is the mental element of a person's intention to commit a crime; or knowledge that one's action or lack of action would cause a crime to be committed. It is considered a necessary element of many crimes."

https://en.wikipedia.org/wiki/Mens_rea

I replied elsewhere but by criminally liable I meant "can be charged".

It may not be how it is supposed to work but how does one defend a drug possession charge when they are in possession of drugs? Just say that the drugs in their backpack aren't theirs?

> It may not be how it is supposed to work but how does one defend a drug possession charge when they are in possession of drugs?

It's the task of the prosecution to establish not just that you possessed the drugs, but also that you intended to possess them.

It's the task of the defense to try to establish that one or both of these things aren't true.

It's the task of the court (probably a jury) to decide whether or not the prosecution has made a case that is beyond reasonable doubt.

So the normal stuff about believing people and possible miscarriages of justice still apply.

My point is just that merely stating that you packed the bags yourself doesn't really establish anything in the prosecution's favour except that it's going to be difficult to later claim that somebody else packed it for you and that you knew this. On the other hand, if they can show that you lied about who packed your bag, then it's probably going to be easier for them to convince a jury that you were up to something (namely drug smuggling). But that mere fact itself doesn't make their case complete, and stating that you packed your own bag certainly doesn't make you criminally liable for its contents any more than you were before this statement.

As to whether you "can be charged": legally, there's no requirement that has to be met to be charged. You could find yourself charged for drug smuggling tomorrow even though you haven't done anything. Whether this will happen or not depends on whether the prosecutor thinks they can win the case. So it probably won't. Saying that you packed the bag certainly doesn't change whether or not they'd win the case for the reasons I gave above.

My comments were in regards to Australian Law.

I think this[0] piece sums up the situation nicely.

There are some very quirky laws here in Australia like "goods in custody" in the state of NSW. Essentially you can be convicted for having items in your possession that the courts "reasonable suspect" were stolen.

There are other things too like Firearm Prohibition Orders (FPOs) which once granted give the police the right to stop and search you even if they don't believe you have committed or witnessed a crime.

[0] - https://newsroom.unsw.edu.au/news/law/drug-prohibition-makes...

> Once you answer yes to this question you are criminally liable for whatever is in the suitcase.

Can you share examples of this happening, where the conviction dependent on that admission?

Perhaps I wasn't clear when I said this. By "criminally liable" I meant "you can be charged". Good luck defending yourself at that point. Possession is possession.

https://www.cdpp.gov.au/crimes-we-prosecute/serious-drugs/dr...

> i immediately go to the police/customs agents for them to inspect my suitcase

Given they didn’t see your suitcase before you sealed it… what can they inspect it for?

Contraband. I assume OP's concern is with someone planting something illegal in his bag.

yes, exactly

If buying tamper-tempting devices online (e.g. powered USB/Thunderbolt docks with access to keyboard/mouse/video), you can order several devices from multiple vendors and look for unexpected delays or routes in shipment progress. Requires some experiments to determine baseline "normal" routes and latency.

For post-delivery tamper deterrence, ship via package receiver and audit home door/window locks, https://news.ycombinator.com/item?id=31856444

If you’re worried about package interception I’d recommend just trying to buy your electronics at a local retailer. Decide which one you’re going to right as you walk out the door so there’s no reasonable way someone can even predict where you’re going.

Though if that’s a legitimate part of your threat model, you’re in a very difficult situation.

> Though if that’s a legitimate part of your threat model, you’re in a very difficult situation.

Its probably (close to) impossible to establish a trust anchor in that situation. That trust anchor being the untampered image. How do you secure that? Yes you can send it to trusted friends, but at that point that just means they're now fair game too. Its definitely not safe on your phone because 0days now definitely are part of your threat model too.

I think maybe if you make it your full time job, you might have a slim chance. But realistically you'd probably only manage that for a limited time.

polaroid?

Sleep?

This may sound overly paranoid, but if they can intercept your deliveries they'll be able to snap a picture of your house key and have covert entry.

You'd probably need to barricade yourself in your bed room so that they cant get in without waking you up. Probably move the bed against the door so it can't be opened.

At some point this just degenerates into requiring unreasonable paranoia and opsec. And unless you have a specific goal to achieve, it may just not be worth it.

Plus airgaps against 0days. It's just purely very not fun I would assume.

While many door locks can indeed be bypassed, it's straightforward for an occupant to keep an inward-opening door closed, by using a $25 door reinforcer, e.g. https://www.homedepot.com/p/Prime-Line-Door-Reinforcement-Lo.... Bypassing that will involve time and noise.

Enterprises hire professionals to provide physical and digital security. In time, they will extend those protections to harden the perimeter of their WFH employees, when needed to protect valuable corporate IP and privileged access. This includes tamper-detection on shipments of corporate equipment to WFH employees.

WFH has likely expanded the number of developers subject to such threats, e.g. those whose enterprise device access-from-home can be leveraged to compromise software supply chains.

Can't find the article but I read that during the cold war US used translucent resin with pieces of aluminium foil to seal high-security rooms, with multiple photos from different angles to capture the 3d arrangement of the foil.

A similar technique exists for non-replicable unique tokens. The token is multiple translucent microspheres pressed together and its authenticity verified by shining a laser on it from different directions and capturing the output.

These topics are interesting. Do you have links to more info on them?

Closest I could find is https://en.wikipedia.org/wiki/Types_of_physical_unclonable_f...

I was wondering if you could defeat the beans/lentils by injecting some water vapor in there (while maintaining the vacuum & placement of the items), and freezing the whole thing. Then cut it open under hard freeze and maybe everything sticks together.

Might even be doable without water vapor at cold enough temperatures. Vapor could damage or cause the rice/beans to start to rot later on, dead giveaway of tampering. Maybe the plastic beads are better in general because of their lack of moisture and general lack of organic weirdness.

plastic beads are also infinitely reusable, although probably have a much higher environmental impact than grains. Gravel could work.

Can we get a warning to those of us with a clearance so that we don't have to self report? Thanks. This turned my day right the hell upside down. Still cool article.

Author- portion markings like that are cool and all, but fml.

No one else is responsible for your bad life decisions.

Ok, I see what you mean. I wonder if you can use a custom Hacker News site/reader that might help somehow?

Can you explain please.

There's an image at the start of the post (I want to say from the Snowden leaks) that's classified TS/SI/NF (top secret, sensitive information, not for release to foreign nationals).

Not a problem for civilians to view actually, but those with government clearance are prohibited from viewing that material unless they are in the allowed categories.

At primary school we had a lid as a desk, and I used to place rulers and a protractor in a certain combination that would be dislodged if open.

OK it could probably be reproduced, and I don’t think I recorded what the position was, but I was only 10 at the time.

Sounds like a fun 3D bin-packing algorithm.

This is one of the coolest anti-tamper mechanisms imho: https://spectrum.ieee.org/the-unhackable-envelope

TLDR: HSM housed within an envelope composed of layered electrodes having a unique capacitive signature used to derive its secret material.

Similar work from another German team.

https://www.hardwear.io/netherlands-2019/presentation/Enclos...

https://media.ccc.de/v/35c3-9611-enclosure-puf

> verifying the authenticity, integrity and/or the physical state of an item by employing the propagation behaviour of electromagnetic waves. In particular, it enables to check for any tamper attempts for larger structures, such as off-the-shelf computers and their periphery. The technology extends existing tamper proof approaches from the chip/PCB to a system level and is easily retrofittable. In this presentation, we are demonstrating exemplary tamper proofing in order to protect secret information without an attack-detection or data-deletion circuit (!), which is a known difficult problem and an imperfect undertaking. Therefore, we demonstrate the simplicity and effectiveness using a very cheap self-made testbed (using alumium foil) to protect standard hardware against invasive attacks, such as needle probing through the case. Cyber-physical systems are ubiquitous and are often located in non-trustworthy environments, in which data is processed that is both sensitive and worth protecting.

That is really cool. I'm surprised, though, something at the femtofarad level doesn't suffer from big swings in behavior/signature based on ambient temperature, moisture, general surroundings, and so on.

Some pressure sensors use the same underlying technique :)

Ah, so add altitude and barometric pressure then :)

I was thinking of touch-pressure, but yes.

I meant as outside influences that could make using the reading as a cryptographic signature difficult.

That is, they are measuring something to do with capacitance (at a very small "femto/10^-15" scale) at the place where they seal it up. Then you're supposed to be able to do that same measurement at the place where it arrives after shipping, and have identical readings. Even though origin and destination likely have different ambient temps, humidity, altitudes, and so on.

Ok, I see what you mean.

Wow that is super cool! What an elegant solution.

My first impression is that a weird shrink-wrapped pack of colored rice'n'beans is gonna trigger any customs agent.

I agree. Anything organic looking that is vac sealed is bound to look suspicious.

I wonder if it would be possible to fill the bag with CO2 and then freeze it, so nothing moves. (Use two tiny needles, and carefully inject CO2 on one side and remove the air from the other.)

Then open it inside of a room kept at dry ice temperatures, do what's needed, and then put everything back.

Let the dry ice sublimate (slowly so nothing moves) and resume the shipment.

Considering dry ice sublimates at -78°C, this is likely to cause cracks or other damage to the equipment being shipped.

> Use two tiny needles

I'm wondering if it would be possible to manufacture some sort of clear plastic sandwich-like material that contains two separate chemical "fillings", kept apart by a central barrier which, if punctured, would allow the chemicals to mix together, triggering a colour-changing chemical reaction.

I guess the problem would be wrapping the target object in a way that couldn't just be unwrapped afterwards, but maybe a glue could be used which creates a chemical bond that is tamper-evident.

That's basically how Polaroid pictures work(ed). The developer/fixer was in the bottom edge, and this container was punctured and the chemicals squeezed out by the rollers as it came out. The only thing left would be to distribute it along the back of the photograph, so you, you know, shake it.

Cold (un)pack.

Love these kinds of problems.

I've always felt for very critical equipment you'd be better off designing a PCB to be physically cracked in two, such that you need both specific halves for it to operate at all, and then ship each half separately. E.g. the electronics version of tearing a dollar bill in half and matching the two halves to verify the identity of the holder (something I've seen in spy movies). You'd probably want to make sure the recipient got the first part before shipping the second, just to make sure.

All modern credit card terminals have this built in. It has a mainboard/sub-board design. In case one or more contacts has been apart, the contents (assuming some kind of keys) on the sub-board are erased, something like a SRAM. Downside is it needs constant power source to keep the content, thus a rechargeable cell is on the board.

Crypto devices used by the government and military have this same sort of tamper identification design. I've seen limit switches hidden behind the front lip of a server so if you pull it out, it triggers the tamper alarm. There are also panels with multiple switches behind so if the panel is opened, alarm triggers. There's layered mesh inside the walls of the devices that will trip the alarm if the layers touch (like with a drill) or if the voltage going through the mesh layer changes (like if you cut through it). Once any seals are broken, the keys inside are wiped and the device is possibly bricked if it really was never meant to be opened. Additionally, screws are JB welded in place so only way you can get in is to either go through the access panel or drill a hole. These things are tempest rated so no one is getting in and nothing is coming out, unless of course you manage to hack it without ever touching it.

Wouldn't help if the chips on the PCB could be replaced.

Am I the only one who's totally unable to spot the apparently-obvious difference in the comparison photo GIF at the end?

It's not as obvious as it could be, because the images were taken from slightly different angles and with slightly different exposure settings, causing a lot of visual distraction.

I was able to clean up the animation a little bit: https://i.imgur.com/cgKSA7H.gif

I'm with you - I noticed that little pac-man, but it's not an optimal way to see the difference. Seems like scaling both images and doing an image diff would be much more effective. That's a standard tool in semiconductor manufacturing.

Maybe even do a perspective transformation + brightness/contrast/hue adjustment and optimize for the parameters which minimize the image difference.

Look at about 8 o'clock roughly 2/3 of the way from the center to the edge.

Used SIFT and OpenCV to align the images a bit better: https://imgur.com/a/vGORFxX

I easily spotted the difference, but the article says “a black lentil in the lower left area has been removed”, and I couldn’t see the removal.

Maybe they meant “a black lentil in the lower left area has been moved, thereby moving another lentil a little bit”? (Seems an easier demonstration to me. Removing a single lentil is trickier than moving one a tiny bit)

Look at around 8.45-9pm (clock dial direction) in the photo, you should see it readily now.

I think this is an interesting but my immediate question is how much are the color matrices affected by normal shipping?

If your intention is to be able to detect tampering during shipping but shipping always causes some disturbance then it probably deserves some discussion?

Vacuum packing small grain-like things like coffee beans/grounds or rice creates a surprisingly sturdy result. I'd be surprised if you could actually move much around without also piercing the plastic.

I've bought products packaged like this before and it's a really odd sensation feeling the bag go from effectively a single solid object to a bag of mush as soon as you release the vacuum.

This effect is used in adjustable casts (these modern plastic ones that you get when you break your foot) and vacuum stretchers for people with a suspected spine injury(+). They’re essentially a bag filled with tiny foam pellets that adjusts to your foot/body shape and turn rock solid once you pump out the air.

(+) https://www.rusunsafety.com/VacuumMattressStretcher/

I'd run across a demonstration of this somewhat recently. I believe it was a video explaining transitions between free-flowing and locked particles, though I don't recall specifically where, and was unable to find it looking for a few minutes just now.

That said: yes, vacuum-sealing good such as beans or coffee grounds provides a surprisingly solid chunk. Releasing the vacuum instantly changes the properties of the mass.

The vacuum packing is tight enough to prevent any significant motion.

Is it? I'm doubtful.

I regularly vacuum pack clothing when I travel and things move enough to change creases even in my carry-on luggage. I'm skeptical that it won't be disturbed in regular shipping unless specific measures are taken.

I used to buy vacuum packed peanuts, there was practically zero chance that they would move around. I also remember that when vacuum packing beddings the result was hard like a brick.

The authors should test if this is actually the case or not.

I think it would be fun to test this with a few people. Let’s vacuum pack some beans and ship them between each other. Sisterhood of the Shipped Legumes.

Email in profile.

I can confirm it. I have a commercial vacuum packing machine, and a bag of rice sealed in it becomes a brick. You can't displace a grain of rice without damaging the vacuum. I doubt that a laptop inside this bag would survive it.

A commercial vacuum packing machine may be stronger than a normal home vacuum cleaner, which the article mentions. Fewer people have access to a commercial machine.

Yeah I was talking about the home vacuum cleaner method. The article mentions that first, but it does go on to mention vacuum packing machines too.

I could see vacuum packing machines possibly working for this.

If I were tasked with dealing with this I would disturb the rice every single shipment, and then let the item continue to its destination.

When every single shipment shows sign of tampering I would expect them to give up on this method.

If you were disturbing every single shipment, I would assume someone was tampering. Once I find a shipping route where none of the items were disturbed, I would know it is secure.

Right, if you are worried about covert tampering and every shipment shows up tampered, you have proven that someone along the shipping route is tampering. You react by distrusting any packages that were previously shipped without anti-tamper protection. And you find a different shipping route. This is costly, but it's a reaction to a threat you can prove to be targeting you.

The tamperer is probably better off not tampering with packages, unless they can do so in a plausibly deniable way.

> I would disturb the rice every single shipment

Increasing attacker costs = success.

It would also increase defender costs, if the defender has to throw out our re-ship some perfectly good hardware every time some of the rice it was packed in was disturbed.

Decoys are a tried and true response to surveillance, with decades if not centuries of best practices.

The shippers would probably find a different way to ship things.

Negative, do not change. While you are incurring a cost to the attacker keep it as is. Ship nulls regularly AND find another method.

Exactly. I would imagine any sort of substantial impact (common in shipping) would shift around some of the pieces.

I believe they attempted to address this via vacuum sealing and cascading bags (if I understood the article).

I wonder whether it would be possible to use isotopic ratios of gases in negative pressure containers or something like that to ensure that any puncture will disrupt the mixture before it can be measured. Hardly foolproof, but anything that an adversary can measure you have to assume that they can reproduce unless you have some way to prove that the process required to reproduce that physical state _must_ take longer than the transit duration.

The other thing that comes to mind would be quantum systems that can only be measured once. Unfortunately I think that practically you would need a system that is "only twice" so that it can be compared, but I have this sense that anything that can be measured twice can be measured 3 times.

Lots of great links here to people working on practical solutions, but in the limit I wonder whether for many of the "black box in enemy territory" models you just have to go with self destruction as the only safe solution because anything less than a fully trusted human being is at risk for being tampered and pwnd (and even then you might still worry).

> The other thing that comes to mind would be quantum systems that can only be measured once. Unfortunately I think that practically you would need a system that is "only twice" so that it can be compared, but I have this sense that anything that can be measured twice can be measured 3 times.

Just spitballing, but you could do it with a "once only" system if you could generate it reliabilly/deterministically enough that you don't need to measure it post-generation

This thought crossed my mind, but I couldn't figure out quite how to get it to work. I think the fundamental flaw with using a deterministic process to create the state is that an adversary can immediately reproduce a matching system if they make the measurement, and then we are back to needing a deterministic process that takes longer to occur than transit time.

After a bit of tangentially related thinking (see below), here is one possible way, and why I don't think it works. One could deterministically create a metastable state in a quantum system, e.g. by pumping a certain specific amount of energy into it. Then to figure out how much energy there was present, any additional amount of energy from by the measurement would cause the state to collapse. Unfortunately having the measured value in hand an adversary could now reproduce that state because the original process is deterministic.

For example, a classic "easy to produce hard(er) to measure" is creating aqueous solutions, where a bunch of different solutes are mixed together (I always think of ACSF, artificial cerebrospinal fluid, because I used to have to make it all the time). The creation of these can be entirely deterministic.

Unfortunately all you need is a good analytical chemist to get an approximation. Even if you used specific ratios of different isotopically pure salts they could probably reproduce it, and you would want something that would cause an irreversible change on physical tampering, such as an oxidation, cleaving, or isomerization so that you couldn't just dump the contents and put them back. All of these are tactics that delay an adversary by presenting them with a measurement and combinatorial problem, but doesn't provide the "measure once" property we need.

Wrap your box with thin copper wire (e.g. as used in transformers). Add tape over the wire. Use a circuit that monitors the resistance of the wire.

Just the wording makes it seem like something TSA would be glad to see as a bomb.

Reading it put me on some Persons of Interest list from the TSA.

That's so simple that it could actually become a product.

Yes, also make sure the wires are visible and suspicious looking.

For extra credit, include some mysterious oozing stuff so it looks like battery acid is leaking.

great idea. Transformer wire has an enamel coating, so for a resistance based system it wouldn't work.

Also I wonder what effect will corrosion/shock have on the resistance ?

Maybe an impedance or inductance based system with enameled wire would be more robust. So many questions, interesting :)

This is cool, but a manufacturer isn't going to vacuum pack your router with rice and beans. So how do you know the thing you are packaging up before sending to someone else wasn't already intercepted before you received it?

Purism charges $300 for their service of tamper-discouraging shipment of a laptop, in an industry where profit margins are historically very low, https://www.cnx-software.com/2020/05/21/purism-anti-interdic...

Other manufacturers may be interested in increasing their slim profit margins via optional packaging services.

At a certain scale, sure, some will, or they'll work with you to setup your own integration process.

fascinating. exactly the type of content I love about Hacker News.

absolutely stunning research and commitment to publishing a free article

I might misremember, but wasn't there something about the use of aluminum flakes in resin for verification in disarmaments, i.e., use a blob of flakes in resin to mark and then check the pattern when about to be scrapped? Could have been just a concept many years back, though. Certainly powerful stuff as very difficult to reproduce at any kind of scale.

Rather than vacuum pack, embedding the device in an expanding foam (mixed with one of these embedded signatures) would serve dual purpose of anti tampering and anti shock.

This seems pretty good if you can randomly embed these signature materials as it expands and then have a record of how they are dispersed in 3D. It’d be hard to duplicate unless the packing foam is repairable and does not leave a trace of reparation if any occurred.

The pattern can be applied to (and sealed onto) the foam after-the-fact.

That said, the loose-bagged option is reusable.

Sealed foam would be an option for initial shipment. The loose-bagged option is more effective against Evil Maid attackes --- frequent periods in which devices or records are left unobserved.

Recently I went to visit my old property and was told of some intrusions.

A simple leaf stuck in the gate made it seem completely natural and at the same time was clear to show it someone opened it.

And it was completely natural to pluck the leaf and stick it in the gate as I was leaving each day.

Vacuum bagging this stuff seems risky... I could imagine a technique could be developed to keep all the coloured beads in place while getting the item out. For example, heating the bag so the beads stick to it? Or flushing through a glue followed by a solvent.

Vacuum sealing something often leaves wrinkles in the bag material, especially when sealing soft items. Those wrinkles are very hard to reproduce if the seal is broken.

That effect could be used to be less 'obvious' that the package is protected.

Perhaps use two stacked meshes and allow it to create a moiré pattern. I'd imagine that would be fairly unique and difficult to reproduce.

Would be interesting to use black and white rice, then convince your phone to read it as a QR code. That'd vastly simplify the before/after comparison.

> An alternative to sealing is embedding the whole object in a substance whose surface forms a mosaic that is difficult to reproduce and changes when manipulated.

The problem with a QR code is the “difficult to reproduce” part —- if you can organize the rice in such a way that it’s recognized as a valid QR code, surely the attacker can recreate the same QR code (or an equivalent, since QR codes have redundancy/ECC).

I wouldn’t want to rely on the vacuum bag method, otherwise you’d be writing off otherwise good devices regularly due to random failure, bag punctures, etc.

Those photos on the article, it's hard to imagine something changing the patterns on those bags not being strong enough to destroy the item inside too. Puncturing those things is quite hard too.

If punctures were a concern, you could seal the inner tamper-evident, vacuum-sealed bag in a second, outer bag (with more rice and beans or perhaps colored styrofoam peanuts if you wanted).

This process could be repeated as many times as you wanted, adding extra layers until the desired level of protection was achieved.

Another approach would be to encase the tamper-evident packaging in wood or metal before putting it in a shipping container.

Isn't this pretty much exactly what the 'Cascading' section of the post already, at least partially, addresses?

Instead of blink comparison, look at the image the same way you do for stereoscopic images.

The difference pop up immediately.

> Instead of blink comparison, look at the image the same way you do for stereoscopic images.

Stare at it for a while, and the sigh frustrated and say whatever, it's the same? Clearly you had more luck with magic eye than I did.

Yes and no.

The cross-eyed (or wide-eyed) option tends to reveal visual discontinuities. Our eyes / visual cortex may register this but it's somewhat inconsistent.

The blink comparison shows an apparent motion, which is a signal our eyes are primed to detect.

I use both methods myself, and find the blink option is far more reliable.

Access to cheap x-ray sensors would be great.

The sensors aren't the issue, it's the X-ray generator that's needed to create the patterns for the sensor to detect.

Looks like you can find $600 dental x-ray machines (probably low quality but that's a low price too) on eBay (source+sensor). That would do a great device for small electronics (assuming you know how to shield, don't be that guy)

If preventing covert entry and modification is important to you, consider this unpickable lock to go with your tamper evident glitter

https://news.ycombinator.com/item?id=31880108

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