Higher Order Masking of the AES

The development of masking schemes to secure AES implementations against side channel attacks is a topic of ongoing research. Many different approaches focus on the AES S-box and have been discussed in the previous years. Unfortunately, to our knowledge most of these countermeasures only address firstorder DPA. In this article, we discuss the theoretical background of higher order DPA. We give the expected measurement costs an adversary has to deal with for different hardware models. Moreover, we present a masking scheme which protects anAES implementation against higher orderDPA. Wehave implemented this masking scheme for various orders and present the corresponding performance details implementors will have to expect.