Researchers from Massachusetts Institute of Technology (MIT) have improved upon the design of a cryptographic ID tag they created years ago.

The tag, which relied on terahertz waves — that are smaller and faster moving than radio waves — originally shared a security vulnerability with traditional RFIDs wherein a counterfeiter could peel the tag off a legitimate item and re-attach it to a fake product and the authentication system would not be able to detect it.

After passing through the tag and striking the object's surface, terahertz waves are reflected, or backscattered, to a receiver for authentication. Source: Ruonan Han, Eunseok Lee, et al

To overcome this security vulnerability, the team leveraged terahertz waves to create an anti-tampering ID tag that is, like its predecessor, still secure and inexpensive.

To eliminate the vulnerability of the tags, microscopic metal particles were added to the glue used to adhere the tag to an object and terahertz waves were then used to detect the unique pattern those particles created on the item's surface. The team explained that this random glue pattern can be used to authenticate the item.

"These metal particles are essentially like mirrors for terahertz waves. If I spread a bunch of mirror pieces onto a surface and then shine a light on that, depending on the orientation, size, and location of those mirrors, I would get a different reflected pattern. But if you peel the chip off and reattach it, you destroy that pattern," the researchers added.

To demonstrate the security improvement, the team produced a 4 sq mm sized light-powered anti-tampering tag and used an accompanying machine learning model to help detect tampering by identifying similar glue pattern fingerprints with more than 99% accuracy.

The researchers suggest that because the terahertz tag is inexpensive to manufacture, it might be possible to implement it throughout the supply chain.

A paper detailing the improvement "A Packageless Anti-Tampering Tag Utilizing Unclonable Sub-THz Wave Scattering at the Chip-Item Interface," was presented at the IEEE Solid State Circuits Conference, held Feb. 18 to 22, in San Francisco, California.