A threshold signature scheme enables distributed signing among $n$ players such that any subgroup of size $t+1$ can sign, whereas any group with $t$ or fewer players cannot. While there exist previous threshold schemes for the ECDSA signature scheme, we present the first protocol that supports multiparty signatures for any $t \leq n$ with efficient, dealerless key generation. Our protocol is faster than previous solutions and significantly reduces the communication complexity as well. We prove our scheme secure against malicious adversaries with a dishonest majority. We implemented our protocol, demonstrating its efficiency and suitability to be deployed in practice.