Trout is a novel protocol implementing the first two-round multi-party ECDSA protocol for arbitrary thresholds. Trout additionally benefits from every participant only having to broadcast an amount of bytes independent to the set size, with the zero-knowledge proofs also having prover complexity independent to the set size. This enables Trout to remain a low-bandwidth option even for large signing sets (100+ nodes).

Included in this repository is a Rust API for working with class groups with a subgroup where the discrete-logarithm problem is easy, as posited within CL15. Included are backends premised on gmp via rug (requiring a C toolchain), malachite (offering a pure-Rust variable-time option), and crypto-bigint (offering constant-time options, believed to be the first of their kind for protocols which build upon CL15). These are not claimed to be optimal, with BICYCL remaining the most efficient option at this time.

Additionally included is the implementation of Trout, as required to enable benchmarking. While the implementation as written with good-practice in mind, it does not always propagate the identification of faulty parties at this time (despite collecting and verifying the zero-knowledge proofs as appropriate) and has not been audited. It is not in any way recommended or endorsed for production use-cases at this time.

The Trout paper, including security proofs, has been accepted to a conference and is planned to published on the IACR ePrint server shortly. Note the paper includes benchmarks using BICYCL to facilitate proof verification and either BICYCL or the crypto-bigint stack backend for proving (depending on whether discussing the numbers for the variable-time or the constant-time prover).

The libraries present in this repository have been improved since and may continue to be actively updated.