International Association
for Cryptologic Research

Before the emergence of inscriptions and ordinal protocols, Bitcoin was limited in its applications due to the Turing-incompleteness of its script language. Fortunately, with recent advances in techniques, Turing-complete off-chain execution layers are established via Bitcoin indexers. Yet, existing indexers have their data integrity and availability strongly dependent on the honesty of indexers. This violated the trustlessness and decentralization principle of the cryptocurrency literature. To provide an alternative Bitcoin indexer scheme and overcome the above limitations, we have reallocated the roles of committee indexers (for heavy computations), normal indexers, and light indexers (the client end), and established a fully user-verified execution layer based on our modular indexer protocol. For the trustless relay of data, we have adopted Verkle trees to store and prove the states. Thus, data integrity and availability are guaranteed even in the case of a majority of malicious committee indexers. Ideally, our modular indexer would safely bridge the gap between the Bitcoin layer-1 and applications from BRC-20, and contribute to the further prosperity of the Bitcoin ecosystem.