Paper 2026/2071 Original: eprint.iacr.org/2026/2071 ↗
Soft Analytical Side-Channel Attacks on SHA-2 and HMAC
Abstract
We investigate the use of bit-level Soft Analytical Side-Channel Attacks (SASCA) to recover secret inputs of the SHA-256 hash function, and secret keys of HMAC-SHA-256, using Sentential Decision Diagrams to overcome the computational challenge posed to classical Belief Propagation by multiple-word modular addition. Our attack on HMAC requires no control nor knowledge of the input, and exploits its double manipulation of the key to improve key-recovery performance. We make comprehensive simulations to evaluate the attacker’s recovery capacity for both SHA-256 and HMAC-SHA-256. Finally, we study the profiling capabilities of load instructions in a multiposition EM probe setup on a STM32F303RET6 microcontroller, and use these results to evaluate the capability of our attack against software implementations of HMAC-SHA-256 in a realistic scenario.
Metadata
- Available format(s)
PDF- Category
- Attacks and cryptanalysis
- Publication info
- Preprint.
- History
- 2026-09-17: last updated
- 2026-09-17: published
- Short URL
- https://ia.cr/2026/2071
- License
- https://creativecommons.org/licenses/by-sa/4.0/
BibTeX
@misc{cryptoeprint:2026/2071,
author = {Maxime Lecomte and Julien Maillard and Antoine Moran and Guénaël Renault and Benjamin Smith},
title = {Soft Analytical Side-Channel Attacks on SHA-2 and HMAC},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/2071},
year = {2026},
url = {https://eprint.iacr.org/2026/2071}
}