International Association
for Cryptologic Research

In this paper, we present the Webb Protocol, a system for building and governing cross-chain applications that can support shared anonymity set functionality across a set of identical bridged systems on compatible blockchains. The Webb Protocol is composed of two major protocols that deal with storing, updating, and validating of data and state changes that occur on a bridge and that are relevant to replicate on each connected chain. State is efficiently verifiable through the use of merkle trees and privacy is provided using zero-knowledge proofs of membership. Together, one can create applications leveraging distributed state with private property testing capabilities. Both financial and non-financial applications are described as motivating examples within the paper.