Succinct Two-Round Two-Party Signing from PCFs

We introduce new two-party threshold signature schemes with strong efficiency and security. The application of our methodology to the two most popular signatures, Schnorr and ECDSA, yields two-round, two-party, stateless and deterministic signing with 4-12 ms of computation on one core of a standard laptop, extremely low communication -- 96 B for Schnorr, and 128 B for ECDSA -- and full concurrent simulatable security. At the heart of our approach is a new pseudorandom correlation function (PCF) for vector-OLE that admits an efficient key generation protocol; we design an end-to-end maliciously-secure and highly parallelizable DKG for this PCF and, using this DKG, we obtain an estimated runtime of 44 s for the (one-time) distributed setup of Schnorr and ECDSA on one core of a standard laptop.