Olingo: Threshold Lattice Signatures with DKG and Identifiable Abort

We present Olingo, a framework for threshold lattice signatures that is the first to offer all desired properties for real-world implementations of quantum-secure threshold signatures: small keys and signatures, low communication and round complexity, noninteractive online signing, distributed key generation (DKG), and identifiable abort. Our starting point is the framework by Gur, Katz, and Silde (PQCrypto 2024). We change the underlying signature scheme to Raccoon (Katsumata et al, Crypto 2024), remove the trapdoor commitments, extend the scheme from two to three rounds, and then apply numerous improvements and optimizations to achieve all the above properties. We provide detailed proofs of security for our new framework and present concrete parameters and benchmarks. At the 128-bit security level, for up to 1024 parties and supporting 2 60 signatures, our scheme has 4.4 KB public keys and 11.3 KB signatures; while signing requires communication of 852 KB per party using the LaBRADOR proof system (Beullens and Seiler, Crypto 2023). An optimistic non-interactive version of our scheme requires only 76 KB communication per party. 1