decrypt.coarticle

A Clever RSA Attack Fooled a Hardware Vault—Here's What It Means for Crypto

Researchers at UC San Diego and INRIA demonstrated a chosen-message oracle attack that forges RSA signatures on a 1,024-bit key held inside a hardware security module (HSM) without ever extracting the key, by disabling the HSM's FIPS mode to get it to sign unpadded/unformatted values roughly 4 billion times and then computing the private-key operation from the responses (1,380 CPU core-years of work). The attack only applies to unpadded RSA signing oracles — standard PKCS#1 v1.5/PSS padding blocks it — so it doesn't threaten Bitcoin/Ethereum (which use ECDSA) but is relevant to anyone auditing HSM key-custody assumptions or RSA-based blind-signature schemes like Privacy Pass. The authors frame it as further classical evidence to accelerate migration away from RSA ahead of the post-quantum transition.