Multi Fault Laser Attacks on Protected CRT-RSA

Since the first publication of a successful practical two-fault attack on protected CRT-RSA surprisingly little attention was given by the research community to an ensuing new challenge. The reason for it seems to be two-fold. One is that generic higher order fault attacks are very difficult to model and thus finding robust countermeasures is also difficult. Another reason may be that the published experiment was carried out on an outdated 8 bit microcontroller and thus was not perceived as a serious threat to create a sense of urgency in addressing this new menace. In this paper we describe two-fault attacks on protected CRT-RSA implementations running on an advanced 32 bit ARM Cortex M3 core. To our knowledge, this is the first practical result of two fault laser attacks on a protected cryptographic application. Considering that laser attacks are much more accurate in targeting a particular variable, the significance of our result cannot be overlooked.