In brief

• Researchers at UC San Diego and France’s INRIA forged RSA signatures on a 1,024-bit key inside a hardware security module, the kind of device custodians use to guard crypto keys, without extracting the key.
• Bitcoin and Ethereum sign transactions with elliptic-curve signatures such as ECDSA rather than RSA, and the paper’s claims cover RSA only.
• The attack needed about 2^32 signing requests (roughly 4 billion) and 1,380 CPU core-years, and the authors say it likely poses no immediate threat to most modern RSA deployments, which use padding.