Evaluation of Magnetoimpedance in Narrow NiFe/Al/NiFe Thin Films for Secured Packaging

The purpose of this study is to evaluate the cybersecurity potential of the giant magnetoimpedance (GMI) effect. To fulfill this objective, it was mandatory to develop the narrowest and the most sensitive GMI element together with an uncommon polarization method that consists in injecting an internal dc bias current in the GMI film to generate a transversal magnetic field in the structure. The impedance of a Ni₈₀Fe₂₀/Al/Ni₈₀Fe₂₀ tri-layer was characterized for different thicknesses, widths, and anisotropy orientations. Each combination of these parameters offers an original outcome of the film that may be used as a specific sensor for cybersecurity purposes. This sensor can be used as an active shield that can be put over a device or included in the package in order to protect it against physical attacks, such as fault injection or invasive attacks. If one of these attacks occurs, any modification of the GMI sensing element induces a change in the impedance response allowing the detection of tampering of the secured packaging. Once the detection is confirmed, various actions can be taken, such as erasing sensitive data or resetting the device.