Plasma Go: A Scalable Sidechain Protocol for Flexible Payment Mechanisms in Blockchain-based Marketplaces

The rapid proliferation of decentralized marketplace applications demands scaling solutions beyond pairwise channels in order to facilitate high volumes of consumer-provider payment transactions. While sidechains seem to present a possible solution, there are several challenges in realizing them; while simpler state channels have seen wide adoption (e.g. Lightning network), sidechains are not in wide use yet. In this work, we propose Plasma Go, a sidechain mechanism for payment transactions where the computational and monetary costs of the required on-chain activity do not depend on the number of sidechain transactions. Indeed, Plasma Go combines pairwise payment channels and the Plasma construct of off-chain activity with root-chain notarization, to yield a mechanism where consumers and providers are guaranteed safety of their sidechain funds without the typical requirement of having them be online. We exploit efficient Boneh-Lynn-Shacham signature and key aggregation schemes to design a notarization and fund withdrawal process that mitigates well-known attacks and drawbacks in previous sidechain designs. We show that the computational load of Plasma Go is orders of magnitudes lower than the state of the art scaling solution. We also analyze the tradeoffs between the signature-based Plasma Go approach and the state-of-the-art sidechain technique ZK-Rollups and highlight a design decision for marketplace operators to make in choosing the Layer 2 solution to use.