Unifying Lightweight Blockchain Client Implementations

Lightweight clients are gaining increasing adoption in existing blockchain deployments, owing to their reduced resource consumption. There are currently a number of libraries that implement lightweight clients (e.g., BIP37, Electrum, LES, filter commitments). Notice that these libraries are intrinsically different and require significant effort to be integrated across blockchain platforms. Additionally, lightweight clients require the cooperation of full nodes, which are expected to invest in their computational (to run filters) and bandwidth resources in order to serve lightweight clients. Existing blockchains however offer no rewards for full nodes in exchange—which offers little incentives for full nodes to correctly serve lightweight clients. In this paper, we shed light on this problem and we show that smart contracts provide a natural and fair environment to deploy and provision filters for lightweight clients. Namely, we propose a scheme, SmartLight, that enables the integration of filters/libraries within smart contracts to support a wide range of lightweight client instantiations. We show that SmartLight can integrate payment routines to reward full nodes to serve lightweight clients. SmartLight can be integrated without modifications in existing blockchains that support smart contracts.