MIT researchers have developed a groundbreaking silk-based tagging system to combat counterfeit seeds, a major contributor to low crop yields in Africa. As described in the journal Science Advances, the system uses minuscule silk dots, each containing a unique combination of chemical signatures, to provide an “unclonable” code that cannot be replicated.
Counterfeit seeds have plagued farmers in many African countries, with the World Bank estimating that up to half of all seeds sold in some regions are fake. This contributes to crop yields that are far below potential, causing significant losses for farmers.
Previous attempts to prevent seed counterfeiting using tracking labels have been unsuccessful due to their vulnerability to hacking. However, the new silk-based tagging system leverages randomness and uncertainty in the application process, making replication virtually impossible.
MIT’s dean of engineering, Anantha Chandrakasan, professor of civil and environmental engineering Benedetto Marelli, postdoc Hui Sun, and graduate student Saurav Maji collaborated on the project, combining their expertise in secure system solutions and silk coating systems.
Marelli explains that a key to the new system is creating a randomly-produced physical object whose exact composition is virtually impossible to duplicate. The labels they create “leverage randomness and uncertainty in the process of application, to generate unique signature features that can be read, and that cannot be replicated,” he says in a press release.
What they’re dealing with, Sun adds, “is the very old job of trying, basically, not to get your stuff stolen. And you can try as much as you can, but eventually somebody is always smart enough to figure out how to do it, so nothing is really unbreakable. But the idea is, it’s almost impossible, if not impossible, to replicate it, or it takes so much effort that it’s not worth it anymore.”
The idea of an “unclonable” code was initially developed to protect the authenticity of computer chips, explains Chandrakasan, the Vannevar Bush Professor of Electrical Engineering and Computer Science. “In integrated circuits, individual transistors have slightly different properties coined device variations,” he explains, “and you could then use that variability and combine that variability with higher-level circuits to create a unique ID for the device. And once you have that, then you can use that unique ID as a part of a security protocol. Something like transistor variability is hard to replicate from device to device, so that’s what gives it its uniqueness, versus storing a particular fixed ID.” The concept is based on what are known as physically unclonable functions, or PUFs.
For the unique silk-based codes, Marelli says, “eventually we found a way to add a color to these microparticles so that they assemble in random structures.” The resulting unique patterns can be read out not only by a spectrograph or a portable microscope, but even by an ordinary cellphone camera with a macro lens. This image can be processed locally to generate the PUF code, then sent to the cloud and compared with a secure database to ensure the product’s authenticity. “It’s random so that people cannot easily replicate it,” says Sun. “People cannot predict it without measuring it.”
And the number of possible permutations that could result from the way they mix four basic types of coloured silk nanoparticles is astronomical. “We were able to show that with a minimal amount of silk, we were able to generate 128 random bits of security,” Maji says. “So this gives rise to 2 to the power 128 possible combinations, which is extremely difficult to crack given the computational capabilities of the state-of-the-art computing systems.”
Marelli says that “for us, it’s a good test bed in order to think out-of-the-box, and how we can have a path that somehow is more democratic.” In this case, that means “something that you can literally read with your phone, and you can fabricate by simply drop casting a solution, without using any advanced manufacturing technique, without going in a clean room.”
Some additional work will be needed to make this a practical commercial product, Chandrakasan says. “There will have to be a development for at-scale reading” via smartphones. “So. that’s clearly a future opportunity.” But the principle shows a clear path to the day when “a farmer could at least, maybe not every seed, but could maybe take some random seeds in a particular batch and verify them,” he says.
While further development is needed to make the silk-based tagging system a practical commercial product, the researchers envision a future where farmers can randomly verify seeds in a given batch using their smartphones. This innovation could significantly reduce the prevalence of counterfeit seeds and improve crop yields for farmers across Africa and beyond.
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Sun, H., Maji, S., Chandrakasan, A.P. and Marelli, B. (2023) “Integrating biopolymer design with physical unclonable functions for anticounterfeiting and product traceability in agriculture,” Science Advances, 9(12). Available at: https://doi.org/10.1126/sciadv.adf1978.