This ‘Tamper-Evident Container’ Snitches on Meddlers and Thieves

Suppose you want to mail a court document to someone across the country—you don’t want anyone to see the secure information inside, of course. So, you seal it into a container that has special sensors built into its walls, and electronics that monitor the shield of sensors. Now, the container is armed and monitoring.

On the way to its intended recipient, let’s say the container is hacked. When the intended recipient later opens the container, they pull out the court document, along with an SD card (just like the ones you might use to store digital photos). They plug the card into a computer and look at the file. They see an encrypted historical record of the container’s experiences, from the time you put that document into the container and sealed it, up until the time they opened it. In the list of messages is a notification about a tampering attack, along with the date and time of the incident. The message also specifies the type of breach detected, such as the container being opened or cut.

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A team at Los Alamos National Laboratory in New Mexico hopes this ability to see recorded, real-time security information about sensitive physical materials will become an everyday tool. Using a 3D printer, engineers built a prototype “Tamper-Evident Container” (TEC) that looks like a cylindrical box on the outside, but inside holds a complex network of sensors and electronics that record potential break-ins.

“So now you have what we call continuity of knowledge of the security of the container,” project lead John Bernardin tells Popular Mechanics. “The idea here was to build a protective sensing network all the way around the container. So if anybody opened it, or tried to break into it did anything, it would alert you. It would know that, hey, I’m being tampered with.”

TECs would work for any shape or size of security container holding materials you want to keep safe from meddling or theft. And, it would be custom-printed for a specific customer’s needs, Alexandria Marchi, an engineer on the project, tells Popular Mechanics. “The beauty of the 3D-printing technique is that you can have many different types of shapes and geometries depending on the type of article you’re protecting.” That means the sensor pattern is also unique to each TEC, making it harder for a hacker to learn how to maneuver past it.

What’s Inside?

Los Alamos National Laboratory

Hidden behind the outermost, visible wall of the container, a dense, hidden network of fiber-optic cables is arranged in patterns. The thread-like cables fill the sides, the lid, and the bottom of the container. Inside the container is a pulsing light source (LED, laser diode, or similar small device) that transmits through the fiber and hits a detector at the end of the fiber called a photodetector. The photodetector is hooked up to a printed circuit board with a microcontroller (a compact, integrated circuit that’s embedded inside a system and acts as the brain of the operation.) The microcontroller commands the light source and acts as a monitor, checking for any interruptions in light reaching the photodetector.

If someone tries to break into the box—say, by drilling or cutting—they will inevitably cut the sensor network. This break in the flow of light will alert the microcontroller, which will trigger a recording of the interruption as tampering. From the time the container is sealed, the system records encrypted messages on an SD card at regular time intervals for proof that the device was working the whole time, Alessandro Cattaneo, an engineer on the team, tells Popular Mechanics. So, the authorized recipient will see a list of messages with timestamps, something like: “System Test, Container Status OK.” If the box experienced tampering, there may be a message like: “Tampering of System Detected.”

The box can contain fiber-optic cables in multiple layers of the wall, because the whole container, complete with cables, is assembled together during 3D printing. “You get more coverage and can hide them better. It’s extremely difficult to penetrate, because of the multiple layers,” Marchi says. Plus, someone tampering with the box wouldn’t be able to alter the messages once they get inside, because they are encrypted, she says.

The prototypes are based on a two-dimensional seal that Marchi and Cattaneo’s team developed back in 2015. Attached to a package with secure contents, it was remotely readable and made with graphite oxide. This is a material with “tunable” electrical properties that are inherently sensitive to tampering attacks, Cattaneo says. However, the printing method involves working with a solvent and was very time-consuming to produce. Inkjet-printing of 2D seals worked better.

How Could We Use Tamper-Evident Containers?

The same technology could be used for a variety of purposes. Here are a few examples:

• A pill bottle, which could be broken from the bottom, leaving the tamper-proof seal on top undisturbed
• A bank vault that could alert a security guard with specific details of a break-in
• A safe that could send its owner a text as soon as an attempted break-in occurs
• Police evidence that’s locked away to preserve DNA integrity
• A valuable painting being shipped across the country
• Valves that need to remain untouched during a sensitive chemical process

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The next step seemed natural: Why not get three-dimensional, full coverage of the item you’re protecting? The team worked on its first 3D concept with Bernardin, using his 3D printers. The project laid out a pattern of electrical traces made of conductive plastic inside an electrically insulating container. The conductive plastic traces were printed into the container wall as it was built.

However, the team moved on to fiber optics to show that they could implement the sensor technology in different ways. The fiber optic cable is “a solid long strand of glass that is unspooled and put into the container wall as it’s built,” Bernardin says in an email. “For certain geometry containers like cylinders, the fiber container can be made much faster than the conductive trace container,” Bernardin adds. “The fiber-optic sensor is also less susceptible to electromagnetic interference [than] the conductive trace sensors for certain applications.” For example, interference from strong magnets or strong electrical fields both interact with the conductive plastic traces in the walls of the container, Bernardin explains.

The bottom line is that the TECs are reusable, can be made cheaply and easily, and can provide indelible, continuous monitoring of many types of secure materials. The group is now trying to find commercial partners to figure out how to manufacture TECs.

In the meantime, the engineers are developing additional functionality for the containers, like sending texts in real time to someone’s phone as soon as tampering occurs. Another idea would add antennas and radio frequency transmission equipment to broadcast the tampering information to interested users.

Because the sensor network automatically protects the contents from tampering attacks, the TECs could include additional sensors to measure all kinds of information, including the orientation of the item, any shocks it receives, or temperature changes. “You can actually record everything that happened. And this could have some changes even on how business is done, because an insurance company might use this information to propose more competitive policy premiums,” Cattaneo says.

The containers could also self-destruct in a way that calls to mind spy thrillers like Mission Impossible, in which the information meant for the spy fries itself before anyone else can see it. This type of “defensive posturing” would deactivate what’s inside, so it can’t be exposed to hackers who penetrate the sensor network, Bernardin says.

Manasee Wagh
Before joining Popular Mechanics, Manasee Wagh worked as a newspaper reporter, a science journalist, a tech writer, and a computer engineer.

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