Key Schedule against Template Attack-Based Simple Power Analysis on a Single Target

Since 2002, there have been active discussions on template attacks due to the robust performance of such attacks. There are reports of numerous proposals to improve the accuracy of prediction model in order to identify the point of interest. To date, many researchers have only focused on the performance of template attacks. In this paper, we introduce a new approach to retrieve the secret information in key schedules, without the profiling phase utilizing secret information. The template attack allows us to reveal the correct key even though the encryption/decryption processes have powerful countermeasures. More precisely, if the templates are sufficiently built in loading/saving the public information, in the extraction phase, the templates already created can be applied to the identical operation about secret information, which allows us to retrieve the secret information even if the countermeasures are theoretically robust. This suggestion becomes another backdoor to avoid hardened countermeasures. In order to demonstrate our proposal, we consider the Advanced Encryption Standard key schedule as a target for attack; however, it cannot be the target of non-profiling attacks in general. Finally, the Hamming weight information of the correct key could be recovered in an XMEGA128 chip, without the secret information. Moreover, we concentrate on the potential possibility of our suggestion since the performance cannot outperform the original methods used in such attacks.