Post-quantum cryptography (PQC) is becoming increasingly critical for securing Internet of Things (IoT) applications against potential threats posed by quantum computers. However, cryptographic schemes based on mathematically hard problems, such as lattice-based constructions, may face reduced security margins due to ongoing cryptanalytic advancements. In IoT use cases requiring long-term deployment without guaranteed secure updates, symmetric-based signature schemes, such as$\mathsf {SPHINCS+}$, whose security relies solely on symmetric primitives, are considered robust alternatives. Among these,$\textsf {AIMer}$, selected as a finalist in the KpqC competition, is emerging as a promising candidate. This article presents optimized software implementations of$\textsf {AIMer}$for various IoT platforms, ranging from low-end to high-end devices. We propose memory-optimized and time–memory tradeoff implementations for resource-constrained ARM Cortex-M4 devices, and single instruction multiple data (SIMD)-accelerated implementations for AArch64 and AVX2 architectures. Furthermore, we conduct a comprehensive performance evaluation comparing our optimized implementations with other PQC signature schemes. Our results show that$\textsf {AIMer}$achieves significantly smaller signature sizes and faster key generation and signing compared to$\mathsf {SPHINCS+}$across all security levels, making it a viable option for long-term IoT deployment.

Abstract Online authenticated encryption has been considered of practical relevance in light-weight environments due to low latency and constant memory usage. In this paper, we propose a new tweakable block cipher-based online authenticated encryption scheme, dubbed , and its domain separation variant, dubbed . and follow the Encrypt-Mix-Encrypt paradigm. However, in contrast to existing schemes using the same paradigm such as and , and enjoy n-bit security by using larger internal states with an efficient -like hashing algorithm. In this way, 2n-bit blocks are processed with only a single primitive call for hashing and two primitive calls for encryption and decryption, when they are based on an n-bit tweakable block cipher using n-bit (resp. 2n-bit) tweaks for (resp. ). Furthermore, they support pipelined computation as well as online nonce-misuse resistance. To the best of our knowledge, and are the first pipelineable tweakable block cipher-based online authenticated encryption schemes of rate-2/3 that provide n-bit security with online nonce-misuse resistance.

Post-quantum signature schemes based on the MPC-in-the-Head (MPCitH) paradigm are recently attracting significant attention as their security solely depends on the one-wayness of the underlying primitive, providing diversity for the hardness assumption in post-quantum cryptography. Recent MPCitH-friendly ciphers have been designed using simple algebraic S-boxes operating on a large field in order to improve the performance of the resulting signature schemes. Due to their simple algebraic structures, their security against algebraic attacks should be comprehensively studied.