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The demand for classical cryptography schemes continues to increase due to the exhaustive studies on their security. Thus, constant improvement of timing, power consumption, and memory requirements are needed for the most widely used classical Elliptic Curve Cryptography (ECC) primitives, suiting high- as well as low-end devices. In this work, we present the first implementation of the Edwards Curve Digital Signature Algorithm (EdDSA) based on the Ed448 targeting the ARM Cortex-M4-based STM32F407VG microcontroller, which forms a large part of the Internet of Things (IoT) world. We report timing and memory consumption results based on portable C and targetspecific hand-crafted assembly code implementations of the lowlevel finite filed arithmetics. We optimize the high-level group operations by implementing the efficient scalar multiplication over the Ed448 isogenous map to reduce the computation complexity. Furthermore, we provide a side-channel analysis (SCA) and fault attack protected design by developing point randomization, scalar blinding techniques, and repeated signature, and evaluate the performance. Our optimized architecture performs a signature and verification in 39.88ms and 51.54ms, respectively, where SCA protection can be achieved at less than 6.4% cost of performance overhead. 

The highly secure Curve448 cryptographic algorithm has been recently recommended by NIST. While this algorithm provides 224-bit security over elliptic curve cryptography, its implementation may still be vulnerable to physical sidechannel attacks. In this paper, we present a speed-optimized implementation on a 32-bit ARM Cortex-M4 platform achieving more than 40% improvement compared to the best previous work. Our design can perform 43 scalar multiplications per second on an STM32F4 working at 168 MHz. At 24 MHz, our proposed implementation takes only 3,740k clock cycles. On the other hand, the security of Curve448 is thoroughly evaluated to have a trade-off between performance and required protection. We apply different effective countermeasures to prevent a subset of side-channel and fault injection attacks at the cost of 8%-22% overhead. 

We present an optimized implementation of the post-quantum Supersingular Isogeny Key Encapsulation (SIKE) for 32-bit ARMv7-A processors supporting NEON engine (i.e., SIMD instruction). Unlike previous SIKE implementations, finite field arithmetic is efficiently implemented in a redundant representation, which avoids carry propagation and pipeline stall. Furthermore, we adopted several state-of-the-art engineering techniques as well as hand-crafted assembly implementation for high performance. Optimized implementations are ported to Microsoft SIKE library written in “a non-redundant representation” and evaluated in high-end 32-bit ARMv7-A processors, such as ARM Cortex-A5, A7, and A15. A full key-exchange execution of SIKEp503 is performed in about 109 million cycles on ARM Cortex-A15 processors (i.e., 54.5 ms @2.0 GHz), which is about 1.58× faster than previous state-of-the-art work presented in CHES’18.