Identity-based cryptographic algorithm SM9, which has become the main part of the ISO/IEC 14888-3/AMD1 standard in November 2017, employs the identities of users to generate public-private key pairs. Without the support of digital certificate, it has been applied for cloud computing, cyber-physical system, Internet of Things, and so on. In this paper, the implementation of SM9 algorithm and its Simple Power Attack (SPA) are discussed. Then, we present template attack and fault attack on SPA-resistant SM9. Our experiments have proved that if attackers try the template attack on an 8-bit microcontrol unit, the secret key can be revealed by enabling the device to execute one time. Fault attack even allows the attackers to obtain the 256-bit key of SM9 by performing the algorithm twice and analyzing the two different results. Accordingly, some countermeasures to resist the three kinds of attacks above are given.

This study concentrates on finding all truncated impossible differentials in substitution–permutation networks (SPNs) ciphers. Instead of using the miss‐in‐the‐middle approach, the authors propose a mathematical description of the truncated impossible differentials. First, they prove that all truncated impossible differentials in an r + 1 rounds SPN cipher could be obtained by searching entry ‘0’ in D ( P ) r , where D ( P ) denotes the differential pattern matrix (DPM) of P ‐layer, thus the length of impossible differentials of an SPN cipher is upper bounded by the minimum integer r such that there is no entry ‘0’ in D ( P ) r . Second, they provide two efficient algorithms to compute the DPMs for both bit‐shuffles and matrices over GF(2 n ). Using these tools they prove that the longest truncated impossible differentials in SPN structure is 2‐round, if the P ‐layer is designed as an maximum distance separable (MDS) matrix. Finally, all truncated impossible differentials of advanced encryption standard (AES), ARIA, AES‐MDS, PRESENT, MAYA and Puffin are obtained.

Correlation Power Analysis (CPA) introduced by Brier et al. in 2004 is an important method in the side-channel attack and it enables the attacker to use less cost to derive secret or private keys with efficiency over the last decade. In this paper, we propose R -squared fitting model analysis (RFA) which is more appropriate for nonlinear correlation analysis. This model can also be applied to other side-channel methods such as second-order CPA and collision-correlation power attack. Our experiments show that the RFA-based attacks bring significant advantages in both time complexity and success rate.