On the scaling of EMFI probes

Electromagnetic fault injection (EMFI), which is a quite recent fault injection technique compared to laser fault injection, has gained in popularity these last years. Its increasing popularity can be probably explained by its inherent advantages among which the limited required preparation of devices can be viewed as the main one. The principle of EMFI consists in generating a powerful EM pulse in the close vicinity of ICs. To that aim a voltage pulse generator is used to induce a sudden current variation in probes, i.e. coils made of several wire turns around a ferrite core. However, EMFI is considered a fault injection technique with a poor spatial resolution mainly because EMFI probes are quite large. Increasing the spatial resolution of EMFI could be achieved by reducing the dimensions of probes. However, such a task is difficult and implies using more powerful voltage generators. Among the challenges to be addressed to enhance the spatial resolution of probes, one of the first ones is to determine how should be scaled the voltage pulse generators with the scaling of probe dimensions. This paper addresses this question from theoretical and practical points of view.