Techniques for EM Fault Injection: Equipments and Experimental Results

Abstract

This paper will show that EM backside injection (case of flip chip bga packages) has little or no interest. Indeed, a new fault injection technique, called Forward Body Biaising Injection (FBBI), must be preferred to EM injection to produce transient faults, especially when LASER shots are detected by the target. The equipment required to apply a FBBI is low cost and really similar to the one used to produce an EM pulse. It is shown in 3. The main difference is the replacement of the coil producing the magnetic field by a thin tungsten rod in order to directly establish an electrical contact with the substrate. With such a direct contact (instead of a magnetic coupling), the fault can be produced with a low amplitude pulse generator. Additionally, the spatial resolution is expected to be better than with an EM pulse. The two electrical behaviors underlying this simple technique will be described before giving some experimental results obtained on a CRT based RSA, running on a secure device featuring a modular arithmetic co-processor.