arXiv subjects

Hanbeom Shin

Publications and source records attributed to Hanbeom Shin.

2 recordsLinked to original sources

arXiv2026

Optimizing Polynomial Multiplication and Fixed-Weight Sampling for HQC on ARM Cortex-M4

In this paper, we present an optimized implementation of Hamming Quasi-Cyclic (HQC) on the ARM Cortex-M4. We optimize (i) the polynomial multiplication and (ii) the support expansion in fixed-weight sampling, and (iii) propose an optional caching strategy that reuses the public transforms and hash recomputed under a fixed key. For the polynomial multiplication, the fixed-constant multiplications in the Frobenius additive FFT (FAFFT) butterfly spend nearly half of their instructions on VMOV data movements between general-purpose and floating-point registers rather than arithmetic. Because minimizing the XOR count alone can increase the total instruction count, we propose a dirty-aware register-allocation policy and an XOR-operation reordering that reduce the VMOV count by up to 48.1% while leaving the XOR count unchanged. We apply these to a multiplication that combines prior FAFFT-CRT methods, and for HQC-1 we further find a 34% sparser FAFFT modulus that lowers the CRT reconstruction cost. For fixed-weight sampling, we rewrite the support expansion with predicated execution and 4-way unrolling, lowering the per-word cost of its inner loop from 22 to 6 cycles while remaining constant-time. On the NUCLEO-L4R5ZI board, our implementation reduces key generation, encapsulation, and decapsulation by up to 33.1%, 34.6%, and 29.8% over the faster of the two prior state-of-the-art implementations, and the optional caching yields a further reduction of up to 32.7% and 18.9% for encapsulation and decapsulation.

cs.AR↗

arXiv2026

MIFA: An MILP-based Framework for Improving Differential Fault Attacks

At ASIACRYPT 2021, Baksi et al. introduced DEFAULT, a block cipher designed to algorithmically resist Differential Fault Attack (DFA), claiming 64-bit DFA security regardless of the number of injected faults. At EUROCRYPT 2022, Nageler et al. demonstrated that DEFAULT's claimed DFA resistance can be broken by applying an information-combining technique. More recently, at ASIACRYPT 2024, Jana et al. improved DFA by searching for differential trails with a single solution. They showed that, for DEFAULT with a simple key schedule, injecting five faults at the fifth-to-last round reduces the key space to one, and for BAKSHEESH, injecting twelve faults at the third-to-last round achieves the same result. In this paper, we propose a new DFA framework that utilizes a Mixed-Integer Linear Programming (MILP) solver. This framework makes it possible to attack deeper rounds than previously achieved, reducing the number of fault injections required for key recovery. Furthermore, we present a method to determine the most efficient fault injection bit positions by systematically analyzing the input differences from all possible single bit-flip faults, thereby further reducing the required number of faults. This systematic analysis has the significant advantage of allowing us to theoretically calculate the required number of faults. Applying our framework, for DEFAULT, injecting three faults at the sixth-to-last round and two faults at the seventh- and eighth-to-last rounds reduces the key space to one.

cs.CR↗