Protective sheath for embedded systems

15.1.2019

Not every burglar needs a crowbar – some of them only need a drill thinner than 1 mm in order to get to data. If their attempt is successful, there can be serious consequences, particularly in sensitive areas such as critical infrastructure, banking and finance, or health care. Businesses and hackers have long been locked in a battle, and the technological tricks are getting more and more sophisticated.

© Fraunhofer EMFT / Bernd Müller

Tamper-resistant foil wrapped around an electronics housing.

© Fraunhofer EMFT

“Stored data can only be decoded if the foil is completely intact,” explains Matthias Hiller from Fraunhofer AISEC.

“Given this background, it is no longer enough to place tamper prevention at the software level only,” says Martin König from the Fraunhofer Research Institution for Microsystems and Solid State Technologies EMFT. In the collaboration between Fraunhofer EMFT and the Fraunhofer Institutes for Applied and Integrated Security AISEC and Microelectronic Circuits and Systems IMS, the expertise from the foil development, security, and microelectronics departments complement one another. The solution resulting from this cooperation provides protection against hostile attacks even at system level: it comprises a tamper prevention foil with an electrically conductive grid structure wrapped around the entire circuit board. “After start-up, individual
fluctuations in production of the foil are surveyed as a physical unclonable function (PUF) in order to inspect the integrity from the inside,” explains Matthias Hiller from Fraunhofer AISEC. If the grid is damaged, this automatically initiates deletion of the critical information such as cryptographic
keys.

Great interest

The system offers reliable protection against drill attacks up to a diameter of 300 μm. Approaches are already being developed to improve this protection further in the future. The Fraunhofer researchers are pleased to be able to report interest from industry even at this development stage. “The feedback from potential customers who have taken a closer look at our solution helps us greatly in orienting our protective foil even more closely to the needs of its later users,” says König. In order to continue preparing the protective foil for use in practice, the research team will also test it fully for security gaps in complex attack scenarios. “To maintain the protective effect of our foil, the integrity of the measuring circuits included must also be tested comprehensively,” says Alexander Stanitzki from Fraunhofer IMS. In the future, it ought to be harder for datathieves to reach the desirable information found inside chips.