(2026-04) ABRA-CAPA-DABRA; Full break of CAPA
2026-04-13
In a paper presented at CRYPTO18, Reparaz et al. introduce a new model called the
Tile-Probe-and-Fault-Model''. This model proposes to cover more realistic side-channel attacks by considering so-calledcombined'' attacks, in other words attacks using both side-channel leakage and fault injection. In addition, they introduce CAPA, a combined ``Countermeasure Against Physical Attacks'', which is inspired by an MPC protocol called SPDZ. In this paper, by attacking the original Beaver triples generation described in CAPA, we demonstrate that the CAPA countermeasure is not secure in its model, by breaking the countermeasures with a simple resolution of a linear system.